[From the U.S. Government Printing Office, www.gpo.gov]























                           PHYTOPLANKTON STUDIES IN THE LITTLE MANATEE RIVER


                              SPECIES COMPOSITION, BIOMASS, AND NUTRIENT

                                     EFFECTS ON PRIMARY PRODUCTION












                                           Gabriel A. Vargo

                                     Department of Marine Science

                                      University of South Florida
















              Funds for this project were provided by the Florida Department of
              Environmental Regulation, Office of Coastal Management using funds made
              available through the National Oceanic and Atmospheric Administration under
              the Coastal Zone Management Act of 1972, as ammended. Local administration
              of this work was conducted through contracts with the Southwest Florida Water
              Management District. Project Manager: Michael S. Flannery.





















                             PHYTOPLANKTON STUDIES IN THE LITTLE MANATEE RIVER

                                SPECIES COMPOSITION, BIOMASS, AND NUTRIENT

                                       EFFECTS ON PRIMARY PRODUCTION













                                             Gabriel A. Vargo

                                       Department of Marine Science

                                        University of South Florida










       f4






                Funds for this project were provided by the Florida Department of
                Environmental Regulation, Office of Coastal Management using funds made
                available through the National Oceanic and Atmospheric Administration under
                the Coastal Zone Management Act of 1972, as anmended. Local administration
                of this work was conducted through contracts with the Southwest Florida Water
                Management District. Project Manager: Michael S. Flannery,














                                               TABLE OF CONTENTS
                                                                                          Page
             LIST OF TABLES


             LIST OF FIGURES


             EXECUTIVE SUMMARY


             INTRODUCTION


             METHODS


             RESULTS
                  Station location                                                           4
                  Salinity                                                                   5
                  Extinction coefficients                                                    5
                  Chlorophyll seasonal cycles                                                7
                  Numerical abundance and composition
                    Tampa Bay                                                                9
                    180/00                                                                  10
                    120/00                                                                  11
                      6o/ 00                                                                12
                      0o/ 00                                                                13
                    Ruskin  Inlet                                                           14
                  Phytoplankton community composition in relation to salinity               16
                  Similarity Index                                                          18
                  Diversity Index                                                           19
                  Cell volume and surface area                                              19
                  Production and nutrient addition experiments
                    Tampa Bay                                                               21
                    180/00                                                                  22
                    120/00                                                                  22
                      00/00                                                                 23
                  Effects of nitrogen and phosphorus additions on
                  short-term photosynthesis                                                 23


             DISCUSSION
                  Community composition and abundance                                       26
                  Nutrient addition experiments                                             30

             POTENTIAL FOR EUTROPHICATION IN THE LITTLE MANATEE RIVER                       32


             REFERENCES                                                                     35


             APPENDICIES                                                                    212












                                                      LIST OF TABLES


                                                                                               Page

                     Table 1     Location of Little Manatee River salinity
                                 stations  and the Tampa Bay station by Rivermile      . . . .  39

                     Table 2     Annual mean values for several parameters in
                                 the LMR.and Tampa Bay arranged in rank order      . . . . . .  40

                     Table 3     Percent of surface irradiance at the maxi
                                 depth attained during the irradiance profile      . . . . . .  41
                     Table 4     The annual mean cell concentration, the median      1
                                 cell concentration, and range, all as cells ml-
                                 for species that occurred 1 13 sample dates during
                                 1988-1989 in the Little Manatee River      . . . . . . . . .   42


                     Table 5     The frequency of occurrence for all species at
                                 each station  . . . . . . . . . . . . . . . . . . . . . .      43


                     Table 6     Similarity index of comparisons between community
                                 composition at Tampa Bay with all LMR stations      . . . . .  49

                     Table 7     Values for the Shannon-Weaver diversity index
                                 for the combined replicate counts for each LMR
                                 station   .. . . . . . . . . . . . . . . . . . . . . . . .     50

                     Table 8     Ratios of dark carbon -14 uptake with and without
                                 the addition of ammonium    . . . . . . . . . . . . . . . .    51














                                                     LIST OF FIGURES


                                                                                                     Page

                  Figure    1.   Map of the Little   Manatee River   and nearby Tampa Bay.
                                 The fixed stations, Tampa Bay and Ruskin Inlet are
                                 indicated. See Table I for salinity zone -locations           . . .   52
                  Figure    2.   Variation in the flow rate (ft    3/sec.) for the Little
                                 Manatee River from January 1988 through January 1989          . . .   53

                  Figure    3.   Seasonal variation in the surface salinity       in Tampa Bay         54
                  Figure    4.   'Seasonal variation in the surface salinity      in Ruskin Inlet      55

                  Figure    5.   Surface temperature in Tampa Bay and two Little Manatee
                                 River salinity zones     . . . . . . . . . . . . . . . . . .          56

                  Figure    6.   Surface temperature for Ruskin Inlet and two Little
                                 Manatee River salinity zones      . . . . . .. . . . . . . . .        57

                  Figure    7.   Variation in the extinction coefficient (-k, 1/m) for
                                 Tampa Bay. Missing values are indicated as blanks in
                                 the plot   . . . . . . . . . . . . . . . . . . . . . . . .            58
                  Figure    8.   Ibid, Figure 7 for 18   0/00  .. . . . . . . . . . . . . . . .        59
                  Figure    9.   Ibid Figure 7 for 12    0/00  . . . . . . . . . . . . . . . .         60
                  Figure    10.  Ibid, Figure 7 for 6 0/00     . . . . . . . . . . . . ... . .         61
                  Figure    11.  Ibid, Figure 7   for Oo/oo    . . . . . . . . . . . . . . . .         62

                  Figure    12.  Ibid, Figure 7   for Ruskin   Inlet  . . . . . . . . . .              63

                  Figure    11,  The relationship between the average annual extinction
                                 .coefficient and the average annualchlorophyll
                                 concentration (Lorenzen calculation) for Tampa Bay
                                 (T.B.), Ruskin Inlet (R.I.) and all other LMR salinity
                                 zones. The solid circles represent actual data points,
                                 the 'Y' values are calculated points for an exponential
                                 relationship, The correlation coefficient, omitting
                                 T.B. and R.J. is 0.99   . . . . . . . . . . . . . . . .               64
                  Figure    14.- The relationship between calculated extinction
                                 coefficients for Tampa Bay and Jeffrey-Humphrey
                                 chlorophyll values. The linear regression is explained
                                 in the text  . . . . . .        . . . . . . . . . . .    o . . .      65

                  Figure    15.  Ibid, Figure 14 for Ruskin Inlet     . . . . . . . . . . . . .        66












                                                                                                      Page
                  Figure 16.     The seasonal cycle of Chlorophyll concentration, as
                                 micrograms per liter (ug/1), based on the
                                 Jeffrey-Humphrey calculation for Tampa Bay. Missing
                                 data points are indicated by blanks in the plot.                      67
                  Figure 17.     Ibid,,Figure 16 for 180/oo salinity zone.          . . . . . .   o    68
                  Figure   18.   Ibid, Figure 16 for 12    0 /oo salinity zone  . . . . . . .     o    69
                  Figure   1 9.  Ibid. Figure 16 for the 6     0/oo salinity.zone,    . . .       .    70

                  Figure   20.   Ibid, Figure 16 for Ruskin Inlet.                                .    71
                  Figure   21.   Ibid, Figure   16 for the 0 O/oo    salinity zone,   . . .. . . .     72

                  Figure   22.   Ibid, Figure   16 for the Wimauma station on the LMR
                                 Data supplied by S. Flannery     . . . . . . . . . . . . . . .        73

                  Figure   23.   Tot al phytoplankton counts (cells/milliliter) for Tampa
                                 Bay . . . . . . . . . . . . . . . . . . . . . . .. . . . .            74

                  Figure   24.   Seasonal variation in the composition of phytoplankton
                                 groups, expressed as a percent of total community
                                 abundance, for Tampa Bay    . . . . . . . ... . . . . . . . .         75

                  Figure 25.     Seasonal variation in the abundance of the diatom,
                                 Skeletonema costatum, in Tampa Bay and two LMR salinity
                                 zones. No symbols are plotted for missing data points.                76

                  Figure 26.     Seasonal variation in the abundance of the blue-green
                                 alga, Schizothrix sp. in Tampa Bay and two LMR salinity
                                 zones . . . . . . .     . . . . . . . . . . . . . . . . . . .         77


                  Figure 27.     Ibid, Figure 24 for Dinoflagellates (Dinofl) and
                                 Chlorophytes (Chlor)    . . . . ... . . . . . . . . . . . . .         78

                  Figure 28.     Ibid'. Figure  24 for Silicoflagellates (Silico) and
                                 Prymesiophytes (Prym)    . . . . . . . . . . . . . . . . . .          79

                  Figure 29.     Seasonal variation in total phytoplankton abundance of
                                 the 180/oo salinity zone. No points are plotted for
                                 missing data  . . . . . . . . . . . . . . . . . . . . . . .           80

                  Figure 30.     Seasonal variation in phytoplankton composition
                                 expressed as a percent of the total abundance for a
                                 particular group at the 180/oo salinity zone. Microfl.
                                   microflagellates, Bl-grn        blue-green algae  . . . . . .       81

                  Figure 31.     Ibid, Figure 30 for Dinoflagellates (Dinofl) and
                                 Chlorophytes (Chlor)    . . . . . . . . . . . . . . . . . . .         82

                  Figure 32.'    Ibid, Figure 30 for Silicoflagellates (Silico) and
                                 Prymnesiophytes (Prym)    . . . . . . . . . . . . . . . . . .         83







                 Figure 33.     TotaL pbytoplankton abundance for the 120   /oo salinity         Page
                                zone. Missing symbols indicate missing data     . . . . . ...     84
                 Figure 34.     Seasonal.variation in the pbytoplankton composition
                                expressed as a percent of the total abundance for total
                                diatoms and microflagellates (microfl) at the 120/00
                                salinity zone . . . . ... . . . .               o . o o . . .     85

                 Figure 35.     Ibid, Figure 34 for Dinoflagellates (Dinofl) and
                                Blue-Green algae (BI-Grn)  . . . . .   o o . . . . .   0 0        86

                 Figure 36.     Ibid, Figure 34 for Chlorophytes (Chlor) and
                                Silicoflagellates (Silico).     . . . . . . . . . . . . . .       87

                 Figure 37.     Variation in total phytoplankton abundance for the
                                60/oo salinity zone. Sampling of this zone did not
                                start until April, however no counts are available     for
                                that month,      o o . . . o           o o . . . . . . . . .      88


                 Figure 38.     Variation in  phytoplankton composition expressed as     a
                                percent of the total abundance for diatoms and
                                microflagellates (Microfl)   . . . . . . . o . . . . o . . .      89

                 Figure 39.     Seasonal variation in the abundance of the diatom
                                Skeletonema costatum at Ruskin Inlet (RI), and two LMR
                                salinity zones.    o . . . .. . . . . . . . . . . ... . . .       90
                 Figure 40.     Ibid, Figure 38 for Dinoflagellates (Dinofl) and
                                Blue-Green algae (Bl-Grn).             o        o . . . . . .     91

                 Figure 41.     Seasonal variation in the abundance of the Blue-Green
                                alga, Schizothrix: sp. at Ruskin Inlet (RI) and the
                                60/oo salinity,zoneo      . . . . . . . . .   o . . . . o         92

                 Figure 42.     Ibid, FIgure 38, for Cblorophytes (Chlor) and
                                Prymnesiophytes (Prym).      o o. . . . . . .   o          o .    93

                 Figure   43.   Seasonal variation in total phytoplankton abundance     of
                                the 00/oo salinity zone  . . . . . .   o      o o . . . . .  o    94

                 Figure   44o   Seasonal variation in phytoplankton composition
                                expressed as a percent of the total abundance for
                                diatoms and Microflagellates (Microfl).       o . . . . . . .     95

                 Figure   45.   Ibid, Figure 44 for Dinoflagellates (Dinofl),
                                Blue-Green algae (Bl-Grn) and Chloropbytes (Chlor)     . . . .    96

                 Figure   46.   Ibid, Figure 44 for Prymnesiopbytes (Prym) and
                                Chrysophytes (Chryso),    . . . o o . . . 97

                 Figure 47.     Seasonal variation in total phytoplankton abundance at
                                Ruskin Inlet.    . . . . . .  o o  . . . . . . . . .   0   0      98











                                                                                                   Page
                  Figure 48.     Varia-tion in the composition of the phytoplankton
                                 community expressed as a percent of the total abundance
                                 for diatoms and Microflagellates (Microfl) at Ruskin
                                 Inlet.     . . . . . . . . . . . . . . . . . . . . . . . .           99

                  Figure 49.     Ibid, Figure 48'fo  r Dinoflagellates (Dinofl) and
                               .Chlorophytes (Chlor)   . . . . . . . . . . . . . . . . . . .        100

                  Figure 50.     Ibid, Figure 48 for Blue-Green algae (BI-Grw),
                                 Prymnesiophytes.(Prym) and Chrysophytes (Chryso)      . . . . .    101

                  Figure 51.,    Variation in the abundance of the Chlorophyte, Eutrptia
                                 sp. in Tampa Bay (TB), and two LMR salinity zones. No
                                 points are plotted for missing data or if the species
                                 was not counted.     . . . . . . . . . . . .    . . . . . . . .    102

                  Figure 52.     Ibid, Figure 51 for Ruskin Inlet (RI), and two LMR
                                 salinity zones  . . . . . . . . . . . . . . . . . . . . . .        103

                  Figure 53.     Seasonal variation in the abundance of the
                                 dinoflagellate, Prorocentrum minimum, in Tampa Bay
                                 (TB), and two LMR salinity zones    . . . . . . . . . . . . .      104

                  Figure 54.     Ibid, Figure 53 for Ruskin Inlet (RI) and two LMR
                                 salinity zones  . . . . . . . . . . . . . . . . . . . . . .        105

                  Figure 55.     Variation in composition of the phytoplankton community
                                 expressed as a percent of the total abundance for each
                                 station and salinity zone on the Little Manatee River.
                                 For each of Figures 55 through 79, which are individual
                                 sampling dates, TB is Tampa Bay, RI is Ruskin Inlet,
                                 and 18ppt etc. are each of the 4 salinity-zones. Each
                                 phytoplankton group is coded as in previous figures.               106

                  Figure   56.   see Figure 55.      . . . . . . . . . . . . . . . . . . . . .      107

                  Figure   57.   See Figure   55.    . . . . . . . . . . . . . . . . . . . . .      108

                  Figure   18    See Figure   55*    * *                                            101

                  Figure   59.   See Figure   55.      . . . . . . . . . .    o o  . . . . . . . .  110

                  Figure   60.   See Figure   55o      . o  . . . ...   o . . . . . . .  o  . . . .

                  Figure   61.   See Figure   55.    . . . . .  o o  o .  o o . o  . . . o  . o o o 112

                  Figure   62.   See Figure   55.    . . .  o           . o . . . . .           0 . 113

                  Figure   63o   See Figure   55.         o . . . . o o   . . . . . . . . . . . .   114

                  Figure   64o   See Figure   55.    010 @  o . o * a o   @ o      o   o    a   o e 115

                  Figure   65.   See Figure   55.    . . . o       o    o o      o              0   116












                                                                                                   Page
                  Figure 66. See Figure 55.           . . . . . . . . . . . . . . . . . . . . .      117

                  Figure   67. See Figure 55.         . . . . . . . . .   o . . . . . . . . . . .    118
                  Figure   68. See Figure 55.         . . . . .  o . . .. . . . . . .   o          o 119

                  Figure   69.  See Figure    55o     . . . . . . . . . . . . . . . . . . . .      o 120

                  Figure   70.  See Figure    55.     . . . . . . . . . . . . . .    0  . . . . . .  121

                  Figure   71.  See Figure    55.     . . . . . . . . . . . . . . . . . . . . .      122

                  Figure   72.  See Figure    55.     . . . . . . . . . . . . . . . . . . . . .      123

                  Figure   73.  See Figure    55.     . . . . . . . . . . . . . . . . . . . . .      124

                  Figure   74.  See Figure    55.     . . . . . . . . . . . . . . . . . . . . .      125

                  Figure   75.  See Figure    55.     . . . . . . . . . . . . . . . . . ... . .      126

                  Figure   76.  See Figure    55.     .          o o . o         o . . .  o . . . .  127

                  Figure   77o  See Figure    55.     . . . . . . . . . . . . . . . . . . .      o . 128

                  Figure   78o  See Figure    55.     . . . . o  . . . o o . o o   . . .  o . .      129

                  Figure   79o  See Figure    55.     .     o .  . o . . . o . o o . o o o . o       130

                  Figure   80.  Seasonal variation    in total   phytoplankton abundance for
                                Tampa Bay (T. Bay)    and two LMR salinity zones    . . . . . . .    131

                  Figure   81.  Ibid, Figure 80 for Ruskin Inlet (R. Inlet) and two LMR
                                salinity zones.       . . . o  . . . . . .  o o . o . o o o . . . 132

                  Figure   82o  Seasonal variation in total diatom abundance for Tampa
                                Bay (T. Bay) and two LMR salinity zones      . . . . . .    o . . o 133

                  Figure   83.  Ibid, Figure 82 for Ruskin Inlet (R. Inlet) and two LMR
                                salinity zones.                  o . . . o       o . o      o . o . 134

                  Figure   84.  Seasonal variation in total microflagellate abundance
                                for Tampa Bay (T. Bay) and two LMR salinity zones,          . . . . 135

                  Figure   85.  Ibid, Figure 84 for Ruskin       Inlet (R. Inlet) and two LMR
                                salinity zones.        o o o . o        o o o o . o . o o . . . o 136

                  Figure   86.  Seasonal variation in total dinoflagellate abundance
                                for Tampa Bay (T. Bay) and two LMR salinity zones. .               o 137

                  Figure   87.  Ibid, Figure 86 for Ruskin Inlet (R. Inlet) and two LMR
                                salinity zones.       . . . o      o 0 0    0    0 . . . . . .   0 0 138












                                                                                                      Page
                   Figure 88.     Seasonal.variation in the     abundance of Blue-Green algae
                                  for Tampa Bay (T. Bay) and two LMR salinity zones.
                                  When Schizothrix was present, counts of filaments per
                                  milliliter were made equivalent to cells per
                                  milliliter.          . . . . . . . . . . . . . . . . . . . . .        139

                   Figure 89.     Ibid, Figure 88 for Ruskin Inlet (R. Inlet) and two LMR
                                  salinity zones.      . . . . . . . . . . . . . . . . . . . . .        140

                   Figure 90.    Seasonal variation in total chlorophyte       abundance for
                                 Tampa Bay (T. Bay) and two LMR salinity       zones . . . . . . . .    141

                   Figure 91.    Ibid, Figure 90 for Ruskin Inlet (R. Inlet) and two LMR
                                 salinity zones.       . . . . . . . . . . . . . . . . . . . . .        142

                   Figure 92.    Seasonal variation in the abundance of the diatom
                                 Chaetoceros subtilus in Tampa Bay (TB) and two LMR
                                 salinity zones.       . . . . . . . . . . . . . . . . . . . . .        143

                   Figure 93.    Tbid, Figure 92   for Ruskin Inlet (RI) and two LMR
                                 salinity zones.       . . . . . .                 . . . . . . . . .    144

                   Figure 94.    Seasonal variation in total-cell volume for the diatom,
                                 Skeletonema costatum (Skel C), and total
                                 microflagellates (Microfl)in Tampa Bay      . . . . . . . . . . .      145

                   Fig  ure 95.  Ibid, Figure 94 only for microflagellates.                             146
                   Figure  96.   I-bid, Figure 94 for the 18   0/oo salinity zone    . . . . . . . .    W
                   Figure  97.   Ibid, Figure 95 for the 18    0/oo salinity   zone.      . . . . . .   148
                   Figure  98.   1bid,, Figure 94 for the 12   0/oo salinity   zone  . . . . . . . .    149
                   Figure  99.   Tbid, Figure 95 for the 120/oo salinity       zone  . .. . . . . . .   150
                   Figure  100.   Ibid, Figure 94 for the 6    0/oo salinity   zone  . . . . . .        151
                   Figure  101.   Ibid, Figure 95 for the 60/oo salinity       zone  . . ... . . . .    152

                   Figure  102.   Ibid,  Figure   94 for Ruskin Inlet.      . . . . . . . . . . . .     153

                   Figure  103.   Ibid,  Figure   95 for Ruskin Inlet.      . . . . . . . . . . . .     154
                   Figure  104.   Tbid,  Figure   94 for the 0 0/oo salinity zone    . . . . . . . .    155
                   Figure  105,,  Ibid,  Figure   95 forthe 00/oo salinity zone      . . . . . ... .    156

                   Figure  106.   Primary production with no nutrient additions for
                                  samples collected in Tampa Bay (Station 1) and the
                                  180/oo salinity zone (Station 3). Each point in the
                                  mean of two replicate determinations.          . . . . . . . . . .    157












                                                                                                     Page
                  Figure 107.    Seasonal variation in the production index in samples
                                 without nutrient additions from Tampa Bay and the
                                 18 0/oo salinity zone. No symbols are plotted for
                                 misssing data points. Productivity values         are
                                 normalized to chlorophyll calculated by the Lorenzen
                                 equations.      . . . . . . . . . . . . . . . . . . . . . . .         158

                                                                            0
                  Figure 108.    Ibid, Figure 106 for the 120/00 and 0 /oo salinity
                                 zones . . . . . . . . . . . . . . . . . . . . . . . . . . .           159
                  Figure 109.    Ibid, Figure 107 for the 120/oo and 0      0/oo salinity
                                 zones.                . . . . . . . . . . . . . . . . . . . . .       160

                  Figure   110.  Seasonal variation in the difference between the
                                 calculated Productivity Index (PI) for samples
                                 receiving the indicated nutrient addition and samples
                                 without a nutrient addition (ONOP). Positive numbers
                                 indicate and average increase in the PI with nutrient
                                 addition while negative numbers indicate a decrease.
                                 Station locations and the type of nutrient addition is
                                 given in the Figure heading.         . . . . . . . . . ...            161

                  Figure 111.    See Figure 110.       . . . . . . . . . . . . . . . . . . . . .       162

                  Figure 112.    See Figure 110.       . . . . . . . . . . . . . . . . . . . . .       163
                  Figure 113.    See Figure 110.       . . . . . . . . . . . . . . . ... . . . .       164

                  Figure 114.    See  Figure  110.     . . . . .  . . . . . . .   e . . . . . . . .    1.65

                  Figure 115.    See  Figure  110.     . . . . . . . . . . . . . . . . . . . . .       166

                  Figure 116.    See  Figure  110.     . . . . . . . . . . . . . . . . . . . . .       167
                  Figure 117.    See  Figure  110.     . .. . . . . . . . . . . . . . . . . . . .      168

                  Figure'118.    See  Figure  110.     .0  . . . . . . . . . .. . . . . . . . . .      169

                  Figure 119.    See  Figure  110.     . . . . . . . . . . . . . . . . . . . . .       170

                  Figure 120.    See  Figure  110.     . . . . . . . . . . . . . . . . . . . . .       171

                  Figure 121.    See  Figure  110.     . . . . . . . . . . . . . . . . . . . . .       172

                  Figure 122.    Seasonal variation    in the rate of dark carbon-14
                                 uptake with the addition of ammonium. Values are the
                                 average of replicate samples. See text for the
                                 calculations. Zero values (no difference between
                                 samples with and without ammonium addition) or
                                 negative values (equivalent to zero) are not plotted
                                 and can not be distinguished from missing data.
                                 Location is given in the Figure heading       . . . . . . . . . .     173












                                                                                                       Page
                  Figure   123. See FIgure 122.        . . . . . . . . . . . .     . . . . . . . . .    174

                  Figure   124. See Figure 122.        . . . . . . . . . . . . . . . . . . . . .        175

                  Figure   125.   See Figure 122.      . . . . . . . . . . . . . . . . . . . . .        176

                  Figure   126.   The relationship between productivity in Tampa Bay
                                  samples incubated without nutrient additions and the
                                  Lorenzen chlorophyll values. The solid line
                                  represents a linear regression calculated omitting the
                                  two data points from May 4 and October 11. See text
                                  for further explanation.         . . . . . . . . . . . . . . . .      177
                  Figure 127.     Same as for Figure 126 with      data from the 180/00
                                  salinity zone.       . . . . . . . .. . . . . . . . . . . . . .       178

                                                                                     0
                  Figure 128.     Same as for Figure 126 with      data from the 12 /00
                                  salinity zone.       . . . . . . . . . . . . . . . . . . . . .        179
                  Figure 12'9.    Scatter-plot of the relationship between the
                                  Productivity Index for the 120/oo salinity zone and
                                  the incubation temperature. See text for further
                                  explanation.         . . . . . . . . . . . . . . . . . . . . .        180
                  Figure 130.     See Figure 126. Data for the 00/oo salinity zone.                     181

                  Figure 131.     Seasonal va  riation in ammonium concentration as
                                  ug-at/l. Station location is given the the Figure
                                  heading. Values in the data set indicated as missing
                                  (-1) are not plotted. Values indicated as less than
                                  0.01 are plotted as zero and thus cannot be
                                  distinguished from true zero values.           . . . . . . . . . .    182
                  Figure 132.     See Figure 131.      . . . . . . . . . . . . . . . ... . . . .        183

                  Figure 133.     See Figure 131.      . . . . .   . . . . . . . . . . . . . . . .      184

                  Figure 134.     See Figure 131.      . . . . . . . . . . . . . . . . . . . . .        185

                  Figure 135.     See Figure 131.      . . . . . . . . . . . . . . .. . . . . . .       186

                  Figure 136.     See Figure 131.      . . . . . . . . . . . . . . . . . . . . .        187

                  Figure   137.   Same as for Figure    131 but for nitrate concentration      . . . .  188

                  Figure   138.   See Figure 137.      . . .  0 . . . . . . . . . . . . . . . . .       189
                  Figure   139.   See Figure 137.      . . . . . . . . . . . . . .. . . .... . .       0 190

                  Figure   140.   See Figure 137   . . . . . . . . . . . . . . . . . . . . . .          191

                  Figure   141.   See Figure 137.      . . . . . . . . . . . . .             . . . . .  192


		

															 Page
	Figure 142. See Figure 137........................................................... 193	
	
	Figure 143. Seasonal variation in total dissolved inorganic
			nitrogen (the sum of ammonium and nitrate) as ug-at/1.
			Station locations given in Figure heading.  Data
			points plotted as indicated in Figure 131................................ 194

	Figure 144. See Figure 143........................................................... 195

	Figure 145. See Figure 143........................................................... 196

	Figure 146. See Figure 143........................................................... 197

	Figure 147. See Figure 143........................................................... 198

	Figure 148. See Figure 143........................................................... 199

	Figure 149. Seasonal variation in phosphate concentration as
			ug-at/1.  Station locations given in the Figure
			heading.  Data points plotted as in Figure 131........................... 200

	Figure 150.	See Figure 149........................................................... 201

	Figure 151.	See Figure 149........................................................... 202

	Figure 152.	See Figure 149........................................................... 203

	Figure 153.	See Figure 149........................................................... 204

	Figure 154.	See Figure 149........................................................... 205

	Figure 155.	Seasonal variation in silicate concentration as
			ug-at/1.  Station locations given in the Figure
			heading.  Data points plotted as indicated in Figure
			131.      ............................................................... 206

	Figure 156.	See Figure 155........................................................... 207

	Figure 157.	See Figure 155........................................................... 208

	Figure 158.	See Figure 155........................................................... 209

	Figure 159.	See Figure 155........................................................... 210

	Figure 160.	See Figure 155........................................................... 211



	

	
			













                                            EXECUTIVE SUMMARY



                  The objectives of the phytoplankton component of the Little Manatee River
             project were to investigate phytoplankton species composition and production in
             the estuary and to assess any limiting nutrient conditions and the potential for
             eutrophication. Field, collections for the phytoplankton Study were done
             simultaneously with water quality sampling between January 1988 and January
             1989. At bi-weekly intervals, nutrients, salinity, light penetration,
             chlorophyll a and phytoplankton counts were measured in the 0 ppt, 6 ppt, 12
             ppt, and 18 ppt salinity zones plus Tampa Bay and Ruskin Inlet. Also, at all
             stations except 6 ppt and Ruskin Inlet, primary production was measured on
             incubated water samples and combinations of nitrogen and phosphorus were added

             to assess nutrient limitation.



                  River flows during the study year were characterized by prolonged low flows
             in the spring and high flows in the summer, most notably a major flood during
             September which flushed the entire river with fresh water and significantly
             reduced salinity in Tampa Bay. Light attenuation, expressed as extinction
             coefficients, was greatest at the low salinity stations and lowest near the
             mouth of the river. Extinction coefficients were positively related to
             streamflow, being lowest during the spring dry period when color concentrations

             in the river were reduced,



                  Chlorophyll a concentrations in the river showed a decreasing trend with
             salinity with the greatest seasonal variation occurring at the low salinity
             stations (0 ppt and 6 ppt). Concentrations were generally lower and less
             variable in the 12 ppt and 18 ppt salinity zones. High river flows during
             August and September reduced chlorophyll concentrations to their lowest values
             throughout the estuary, but maximum concentrations were recorded at most
             stations shortly thereafter during a period of decreased river flow which

             allowed restabilization of the water column,



                  The phytoplankton community in the Little Manatee River and adjacent area
             of Tampa Bay consisted primarily of a seasonally varying mixture of diatoms,
             dinoflagellates, microflagellates and chlorophytes with a sporadic occurrence of

                                                   iii











            blue-green algae. With the exception'of a few dates, diatoms or micro-
            flagellates were the dominant groups at all stations. Many algal species were
            found to occur regularly throughout the estuary, suggesting that upriver
            transport of bay water with accompanying cells occurs regularly. However,
            pronounced spatial differences in species composition were observed in the
            estuary and periodic blooms occurred at different times in the various salinity
            zones. Diatoms were most consistently abundant at the Tampa Bay station where
            they averaged 44.8% of total cell counts. Microflagellates were the co-dominant
            group in the bay except during a late summer-fall bloom of the blue-green alga,
            Schizothrix, which occurred in the bay and river after the September flood.
            Microflagellates were generally the dominant group at all river stations,
            particularly the intermediate salinity zones (12 and 18 ppt) and the low
            salinity zones during the summer. Estimates of total cell volume, however,
            showed that this group of small, unidentified species usually comprised less
            total volume than the diatoms. Of all the river stations, total phytoplankton
            counts were highest for the 0 ppt salinity station. Diatom blooms were more
            frequent at this station compared to intermediate salinity zones. Chlorophytes
            were most abundant at this station with a maximum abundance of 7% of total cells

            in late September. High phytoplankton counts and chlorophyll concentrations at
            the 0 ppt station were most likely due to primary production within the upper
            estuary since chlorophyll concentrations at the most downstream freshwater site
            were consistently low. Chlorophyll and phytoplankton counts were reduced at the
            0 ppt station during the summer, due possibly to flushing of the upper estuary'
            by medium to high river flows. Of all the study sites, total phytoplankton
            counts were highest at the Ruskin Inlet station, a eutrophic, channelized inlet
            to the river 2.5 miles above its mouth. At this statio@ there was an almost
            continuous presence of euglenoid flagellate species which are phagotrophic and
            indicative of high organic particle loads.


                 Primary production rates in the river generally followed trends observed
            for chlorophyll concentrations and cell counts, with highest values occurring  at
            the 0 ppt station and progressively decreasing values found.in the 12 ppt and
            18 ppt salinity zones. In short-term (3 hour) experiments, enrichment of
            samples from Tampa Bay and three river stations with combinations of nitrate and
            phosphate did not show a consistent enhancement of photosynthesis. Additions of
            ammonium to dark incubated samples gave results indicating that waters from











             Tampa Bay and the river could be considered nutrient sufficient or borderline
             nitrogen-limited with regard to short-term photosynthesis. Ambient water column
             concentrations of ammonium, nitrate and phosphate indicated that phosphorus was
             always present in excess, while ammonium and nitrate concentrations varied
             considerably and at times were at the limit of detection.


                  The results indicate that short-term phytoplankton production in the
             estuary is not usually nutrient limited, but long-term nutrient limitation of
             growth or biomass may occur. Ong oing second year experiments conducted on
             waters from the 12 ppt zone have shown that nitrogen additions alone can result
             in dramatic long-term increases in chlorophyll levels. Although short-term
             photosynthesis may not be limited with regard to ambient nutrient levels,
             increased nitrogen loading should result in increased phytoplankton levels in
             the estuary and the potential for eutrophication if such loading occurs is high.













                       INTRODUCTION



                             The  Little    Manatee    River    project   was   designed    as    a
                       multi-disciplinary, multi-agency      study    of  a  moderately    impacted
                       watershed in the Tampa Bay estuarine system.       The first year of this
                       study was designed to provide basic information about the physical,
                       chemical and biological components of the river that could be'used for
                       future management decisions.
                             The objectives of the phytoplankton component of this study are to
                       provide information on the seasonal and spatia     1 variation in species
                       composition and to conduct nutrient addition experiments to assess
                       potentia 1 nutrient limitation of this com   munity and the potential for
                       eutrophication in the Little Manatee River,



                       METHODS



                             Water samples for pbytoplankton abundance and species composition
                       were collected twice monthly at 5 locations, in the Little Manatee River
                       and at a station in Tampa Bay, approximately 2.3 miles northeast of the
                       mouth of the river (Fig. 1). Additional water samples for determining
                       the effect of nitrogen and phosphorus additions on carbon-14 uptake by
                       these same populations were taken at 3 of the river stations and at the
                       Tampa Bay station.. Tampa Bay and Ruskin Inlet, in the Little Manatee
                       River, were the only fixed locations.        Rusk in Inlet is a channelized
                       inlet off the Little Manatee River which is surrounded by urban
                       development (Fig. 1). The remaining station locations were determined by
                       salin ity so their geographic location varied throughout the year (see
                       Table 1).     Phytoplankton . abundance and species composition were
                       determined at the following locations and salinity zones: Tampa Bay, 18
                       O/oo, 12 O/oo, 60/oo, Ruskin. Inlet,      and 0 O/oo.     Samples from two
                       stations, the mouth of the river and 9 /oo , were collected on the first
                       two sample dates (1/26/88 and 2/10/88) but were not sampled thereafter.
                       Two other salinity zones, 120/oo and 60/oo replaced these two earlier
                       stations.   Results from the mouth and 90/oo will not be discussed in
                       this report.    Nutrient effects on carbon-14 uptake were determined at
                       Tampa.Bay, 12  0/oo, 6 O/oo and 0 O/oo.











                           Replicate surface samples were taken at each location. Subsamples
                      for one cell count and species composition and carbon-14 uptake were
                      taken from the first replicate after screening the water through a 153
                      um Nitex mesh net to remove detritus and larger zooplankton. The second
                      cell count  sample was taken from the second replicate after screening
                      through the same Nitex mesh. Subsamples for counts and composition (100
                      ml) were    preserved in the field with 2% (final concentration)
                      neutralized formalin and kept dark and cold for transport to the
                      laboratory.    Subsamples for carbon-14 uptake were kept at field
                      temperatures, in the dark, for transport to the laboratory, usually
                      within two hours after collection.          These samples were normally
                      processed within 1-2 hours after return to the laboratory. The same set
                      of replicate water samples was also used by others (SWFWMD, Brooksville
                      Laboratory). for the determination of dissolved nutrients (nitrate,
                      ammonium, phosphate, silicate) and particulate carbon, nitrogen and
                      phosphorus.   Methodology for these analyses can be found in their
                      report. Chlorophyll-a concentrations were determined by FDNR, FMRI, St.
                      Petersburg Laboratory, on each of the replicate surface samples.
                      Chlorophyll was determined spectrophotometrically and concentrations
                      were calculated using two methods: The Lorenzen method (Lorenzen, 1967)
                      which accounts for the presence of phaeopigments, and the standard
                      Jeffrey and Humphrey equations (Jeffrey and Humphrey, 1975) which does
                      not. Both values have been used in this report.        Seasonal chlorophyll
                      cycles are depicted using the Jeffrey and Humphrey calculation since
                      there were several sample dates which were not available from the
                      Lorenzen calculation and because the Jeffrey and Humphrey values more
                      closely   reflected    the   seasonal   variations   in   species     counts.
                      Chlorophyll concentration based on the Lorenzen method is, however, used
                      in the calculation of the productivity index.       Since carbon-14 uptake
                      only occurs in living phytoplankton, the Lorenzen calculation, which
                      corrects for chlorophyll degradation products associated with dead
                      cells, yields an accurate representation of primary production.          When
                      Loren zen chlorophyll values were not available, the productivity index
                      was calculated using the Jeffrey and Humphrey value and will be noted in

                      the text.





                                                            2











                            A single count for phytoplankton abundance and species compostion
                       was  made on- each of the replicate samples using a'*Sedgewick-Rafter
                       counting chamber (I ml volume) on an Olympus phase contrast microscope.
                       Three to seven longitudinal  paths were counted depending upon abundance;
                       microflagellate counts are based on a single path    *  Thus 25-50% of the
                       chamber volume was counted. Periodic determinations were made for the

                       cumulative number of species identified by counting additional paths.
                       The first path accounted for 50-68% of the total species while 83-95%
                       were found within 3 paths. Cell size measurements were made on as many
                       species as feasible. A total of 43 species or groups had shapes which
                       would   yield   measurements    applicable   to   geometric   formulae    for
                       calculation of cell volume (um  3) and cell surface area (um 2). Cell size
                       measurements were made microscopically and with an Image Analyzer

                       System.
                            The effects of nitrogen and phosphorus additions on the potential
                       photosynthetic rate, as measured by carbon-14 uptake, was assessed by
                       partitioning the subsample of the first surface replicate into 60 ml,
                       acid cleaned, glass bottles.       Nitrogen (N) and Phosphorus (P), as
                       nitrate and phosphate, were added to each set of duplicate bottles as
                       follows:   0 N and P; 5 uM N, OP; ON, 2 uM P; 5 uM N, 2 uM P.              in
                       addition,  5 uM N as ammonium was added to 2 additional dark bottles to
                       determine  the effect of N-enhanced dark carbon-14 uptake. An additional.
                       set of duplicate bottles from the 0     0/00 station were used as initial
                       bottles (zero-time controls). This station was chosen since it normally
                       had the highest particulate load.      The initial' bottles were filtered
                       immediately after the addition of one microcurie of carbon-14 to
                       determine the ef fect of adsorption and could also be used to correct the
                       light bottle uptake rates if dark bottle uptake was high (Carpenter and
                       Lively, 1980). However, dark bottle (without added ammonium) rates were
                       always- 10% or less of the light bottle uptake.       Therefore all uptake
                       rates were corrected using dark bottle counts.          The initial bottle
                       counts were not used.     One. microcurie of carbon-14 was added to the
                                                                                -2  -1
                       remaining bottles and they were incubated at 300 uE m        8   for 3 hours
                       at the average ambient river temperature. Temperature was controlled by
                       a circulating water bath. After incubation each bottle received 1 ml of
                            -5
                       a 10    molar DCMU solution to stop further carbon uptake (Eppley and


                                                             3










                      Renger, 1974; Bienfang and Szyper, 1981).     Samples were then filtered
                      onto 0.4 um--Nuclepore filters, dissolved in  a suitable tissue solvent,
                      and after the addition of a scintillation     cocktail, counted in a TM
                      Analytic scintillation counter.    Counts were corrected for quench and
                      DPM (disintegrations per minute) calculated using a known standard and
                      the external standard ratio method.    Carbon uptake was then calculated
                      by the appropriate equations in Strickland and Parsons (1972).       Total
                      carbonate in the sample, which is required for the calculation of carbon
                      uptake, was determined on an Oceanography International Total Carbon
                      Analyzer using triplicate 0.5 ml subsamples of the water used for
                      measurement of carbon-14 uptake.
                          In addition to the above samples and analyses, light measurements
                      were made at all stations. A Li-Cor quantum sensor was used to obtain
                      irradiance readings of Photosynthetica lly Active Radiation (PAR, 400-700
                      nm) at the surface and approximately 0.5 m intervals throughout the

                      water column with a final measurement as close to the bottom as
                      practical.  An extinction coefficient (k) was determined from these
                      readings as the slope of an exponential curve fit of the data.-



                      RESULTS



                      Station Locations



                          The Tampa Bay and Ruskin Inlet stations were the only fixed
                      locations.sampled during this study (see Fig. 1 and Table 1). The Tampa
                      Bay station was located approximately 2.3 miles northeast of the mouth
                      of the Little Manatee River, with Ruskin Inlet approximately 2.5 miles
                      eastward from the mouth.     All other river stations were sampled as
                      regions of constant salinity, therefore their geographical locations
                      varied- throughout the year (Table 1).     Thus, the 180/oo and 120/oo
                      salinity zones were occassionally located outside the mouth of the river
                      in Tampa Bay (Table 1).    During periods of high river discharge (see
                      Fig. 2; e.g. August 30 and September 8, 1988) all salinity zones were
                      located at the mouth of the river or in Tampa Bay. All salinity zones
                      showed a wide geographic variation in their respective locations (Table
                      1).



                                                           4











                         Salinity


                                The seasonal cycle of salinity at Tampa Bay and Ruskin Inlet
                         (Figs. 3 and 4), for those 'dates when salinities are available, is
                         related to variations in river flow (see Fig. 2).        Reduced salinity at
                         both locations in March, July, August and September correspond to
                         periods of increased river flow. :Low river flow during spring and early
                         summer yielded steadily increasing salinity at Ruskin Inlet with values
                         greater than 20   0/00 in late June and early July.           The series of
                         increases and decreases in salinity with a frequency of 2-4 week
                         intervals at Ruskin Inlet during the fall and winter of 1988 and 1989
                         also correspond to variations in river flow. Salinities increase within
                         the 2-week sampling time-frame which suggests relatively rapid mixing
                         with higher salinity water from the river or Tampa Bay.
                         Temperature


                              All locations show a similar seasonal cycle a              nd range of
                         temperature (Figs. 5 and 6).       Rapid reduction in temperature      I during
                         March and September correspond to periods of high river              flow and

                       .increased runoff whereas the decline noted at all locations in

                         November /December was not associated with riverflow.       Winter minima at
                         all locations was 14  0C with summer maxima of approximately 30      0C.    The
                         variation in temperature at any location for a particular sample date
                         was generally within 1 to 2 degrees.




                         Extinction Coefficients



                              Extinction coefficients are calculated as the slope of an
                         exponential curve fit to the fraction of light reaching a given depth
                         versus depth. Therefore, the slope of the line will be higher if light
                         is attenuated rapidly.      Clear, particle free water will have a low
                         exticntion coefficient. The values' are given a negative numbers since
                         they have a negative slope however, a high negative number (i.e. -2.5
                         vs. -0.5) indicates a high extinction coefficient and turbid water.




                                                                5










                            Annual mean values for the extinction coefficient of light
                       attenuation-in the water column increase from the lowest value in Tampa
                       Bay to the highest at the fresh-water station at the head of the river
                       (Table 2).    The 180/oo station had the lowest value for all river
                       stations which corresponds to its ranking for total cell counts and
                       chlorophyll concentration.
                            Seasonal cycles for light attenuation at all stations are seen in
                       Figs. 7 to 12.     All stations show considerable variation that can be
                       related to both streamflow and phytoplankton biomass as chlorophyll.
                       Streamflow alone does not control the extinction coefficient except in a
                       general sense. Lower values (deeper light penetration) occur during the
                       April to early July period of low, constant river flow (see Fig. 2)
                       whereas values at the LMR stations increase during periods of high river
                       flow (August - September).      This is particulary true for the 00/oo and
                       Ruskin Inlet stations where maximum extinction coefficients coincide

                       with periods of increased stream flow.

                            The annual mean extinction coefficients at 4 of the LMR stations
                       can be related to the annual mean chlorophyll concentration (Fig. -13).
                                                                                 2
                       The relationship fits an exponential curve with an r         =  0.99. Tampa Bay

                       and Ruskin Inlet show annual mean coefficients that are lower for a
                       given chlorophyll level than corresponding LMR stations.               Extinction
                       coefficients for Tampa Bay and Ruskin Inlet were plotted against the
                       Jeffrey-Humphrey chlorophyll values for each sample date to determine if
                       a relationship existed. A linear relationship gave the best fit between
                       the two parameters for Tampa Bay (Fig. 14), however,            the correlation
                                          2
                       coefficient of r    .  0.60 (deleting the October 11 data       point) suggests
                       that   fa ctors   other    than   phytoplankton     biomass     (e.g.    sediment
                       resuspension or water color) were contributing to the observed light
                       attenuation.      No  relationship was found between            the calculated
                       extinction coefficient and chlorophyll at Ruskin Inlet          (Fig. 15). The
                       calculated line in that f igure is the same as the 9            easonal average
                       (1.91, Table 2).       Therefore, as in Tampa Bay, factors other than
                       phytoplankton biomass determine the extinction coefficient.
                            Based on the annual average extinction coefficient, the calculated
                       depth of the 1% light level.ranges from 1.59 to 4.0 meters for the 00/oo
                       and Tampa Bay stations, respectively.        Since the bottom depth at most



                                                               6










                        all stations. is 2.5m or less, all locations should have an autotrophic
                        water columsi. -The variation in percent of surface irradiance at each
                        location for each sampling date confirms this (Table 3).         Although the
                        Oo/oo location had less than .1% surface irradiance on 9 of 26 sample
                        dates, the annual average extinction coefficient (Table 2) suggests that
                        the water column at this salinity zone will be completely autotrophic.


                        Chlorophyll a seasonal cycles


                             All seasonal cycles of chlorophyll a .(Chi) shown in Figs. 16 to 22,
                        are based on the values determined by the Jeffrey-Humphrey calculation.
                        In Tampa  Bay the seasonal cycles can be characterized by winter minima
                        (concentrations less than 6 ug -1       -1 . January to March, 1988 and
                        November-December, 1989) with summer-fall.maxima. Concentrations ranged
                        from less than 1 ug 1-  1 to approximately 34ug 1-   1 (Fig. 16). During the
                        period of June through August, concentrations remained relatively
                        constant-at 10 to 15 ug I        The minimum that occurred on September 8,
                        1988 coincides w1th periods of high river flow (Fig. 2) and reduced
                        salinity   (Fig. 3).      The September- October chlorophyll maximum
                        corresponds to a period when river flow stablize          ,d af ter the early
                        September f low maximum. At this time a bloom of the blue-green alga,
                        Schizothrix sp. occurred in Tampa Bay and the LMR (see below).              The
                        annual mean chlorophyll a concentration was 7.46 ug 1-     1 and ranked fifth
                        among the 6 stations (Table 1).
                             Chlorophyll concentrations at 18 O/oo were generally lower than in
                        Tampa Bay with a maximum of 10 ug 1            occurring in May (Fig. 17).
                        Winter values were similar in magnitude to Tampa Bay with relatively
                        constant conce  ntrations during Ju   ne and July.     The September-October
                        maximum seen in Tampa Bay did not occur at this salinity zone although
                        Schizothrix was present. This salinity zone was found in Tampa Bay from
                        August 30, 1988 through December 8, 1988,and at the specific location of
                        the Tampa Bay station on September 22 and October 11 (see' Table 1).
                        .Therefore, chlorophyll values assigned to Tampa Bay for these dates in
                        Fig. 16 can also be interperted as occurring at the 18          0/oo salinity
                        zone.   However, they were not included in calculating the annual




                                                                7











                      averages listed in Table 2. The annual mean concentration of 4.27 ug
                      1-1was the-lowest of the 6 stations sampled (Table 2).
                           At the 12 O/oo salinity zone, chlorophyll concentrations displayed
                      a cycle that differed from Tampa Bay and 18 O/oo with a maximum in
                      early July (Fig. 18)..     Winter minima were followed by relatively
                      constant levels (10 ug 1-     1) during April and May.        A series of
                      short-lived blooms occurred during August and September. This salinity
                      zone also, occurred at the specific location of the Tampa Bay station on
                      September 8, 1988 (see Table 1).        Scbizothrix was present at this
                      salinity on that date.    Chlorophyll values assigned to Tampa Bay can
                      therefore be interperted as occurring at this salinity zone. The annual
                      average chlorophyll concentration at this salinity zone was
                       9.41 ug 1-1 and ranked fourth among the 6 stations (Table 2).
                           The seasonal cycle of chlorophyll at 6   0 /00 (Fig. 19) differs from
                      all other stations with the exception of the August-Sept ember minimum
                      that corresponds to the period of high river flow.      This salinity z  one
                      can best be characterized by a series of blooms with a periodicity that
                      varies from semi-monthly to monthly. The annual maximum occurred in May
                      when the phytoplankton community was dominated by microflagellates and a
                      small Cyclotella sp.. This species was also found at the 00/oo salinity
                      zone on this date.    The annual average chlorophyll concentration was
                      13.63 ug 1- 1, which ranked third highest of the 6 stations (Table 2).
                           Chlorophyll concentrations at Ruskin Inlet (Fig. 20) also    display a
                      cycle which indicates that a series of blooms occurred with about a 1
                      month frequency.    The August-September flushing event also reduced
                      chlorophyll levels at this station. Chlorophyll concentration increased
                      rapidly after the flushing event to the annual maximum of 50 ug 1-     1  in
                      early,November. This peak occurred about one month later than in Tampa
                      Bay.   Cblorophy 11 concentration fluctuated between 10 and 25 ug 1
                      during- the rest of the year with an annual average of 17.79 ug I-
                      (Table 2).
                           The 0 O/oo salinity zone had the greatest annual range of
                      chlorophyll concentrations, varying   from approximately 1 ug 1-   1  during
                      the August-September flushing event, to a maximum exceeding 60 ug 1-   1  in
                      late October when river flow stablized (Fig. 21). Minimum values were
                      found in January 1988 and 1989 and during August-September 1988.         The



                                                            8








                        annual average was    18.32 ug 1-  1  whi ch was the highest of all LMR
                        stations and Tampa   Bay  (Table 2).   The seasonal cbloropbyl.1 cycle at
                        this salinity zone   can also be described as a series       of short-lived
                        blooms with concentrations seldom falling below 10 ug 1   -1
                             Chlorophyll concentrations from the Wimauma station      'on the Little
                        Manatee River are included in this report for comparison     with the 00/oo
                        and other Little Manatee River salinity zones (Fig.22).           They were
                        obtained from Mr. Sid Flannery, SWFWMD.           Althought there are a
                        considerable number of missing values, the general trend at Wimamuma
                        appears to be a, series of short-lived blooms with approximately a
                        monthly periodicity.    The outstanding feature of the seasonal cycle at
                        th is location is the low chlorophyll concentrations. The maximum that
                        occurred-in late July was less than 8 ug 1-   1 with most other values less
                                     1
                        than 4 ug 1-  .  Therefore, the chlorophyll concentration at Wimauma was
                        considerably less than that recorded at the freshwater salinity zone
                        (00/oo)' and at the 180/oo salinity zone; the regio      n with the lowest
                        annual average for the River. Elevated chlorophyll concentrations at the
                        00/oo zone therefore were the result of pbytop*lankton growth between
                        Wimauma and 0   0/oo rather than transport from Wimauma, which is
                        considerably east of the 00/oo salinity zone.
                             In general terms, the period of increased river flow in August and
                        early September reduced chlorophyll concentrat    ions at all LMR stations
                        and Tampa Bay to their annual minimum.        Major blooms 'developed at 3
                        stations (Tampa Bay, Ruskin Inlet and 0 O/oo) shortly thereafter, during
                        a period of decreasing river flow (Fig. 2) which should allow
                        restablization of the water column. At all other times of the year, the
                        seasonal cycle of chlorophyll at all LMR stations can be characterized
                        as a series of blooms with a semi-monthly to monthly frequency that show
                        little relationship to river flow characteristics.


                        Numerical abundance and composition



                        Tampa Bay


                             Elevated numerical abundance in January and February, 1988 (Fig.
                        23) was not reflected in the seasonal chlorophyll cycle (Fig. 16).
                        Diatoms, primarily Skeletonema costatum, dominated during this period

                                                              9











                      and into March (Fig. 24 and 25).    Low and essentially constant total
                      populat ion -density occurred during the period of low river flow from
                      March through mid-June (Fig. 22) which did not reflect the variable and
                      elevated chlorophyll levels measured during that time period. The bloom
                      that occurred at, the end of June was dominated by the diatom
                      Thalassionema nitzschoides, while S. costatum and Nitzschia pungens, a
                      chain forming pennate diatom, were dominant during the July 28, 1988
                      peak of abundance.     Diatom abundance decrease during spring and
                      displayed an inverse cycle with microflagellate populations (Fig. 24).
                      The two groups contributed greater than 80% of. the total population
                      throughout most of the year. Exceptions to t.his generalization occurred
                      during the period of high river flow during August-Sep t ember, 1988 and
                      September-October when the blue-green alga, Schizothrix sp. became the
                      numerical dominant (Fig. 24 and 26). This latter bloom coincided with
                      the annual chlorophyll maximum (Fig. 16). Schizothrix first appeared in
                      early August when river flow increased (Fig. 2) and salinity decreased
                      (Fig. 3) and persisted to the first November sampling. This blue-green
                      alga was present throughout Tampa Bay during this period (COT, pers.
                      comm.)
                          Dinoflagellate populations were present throughout the year (Fig.
                      27) but never represented more than 5% of the total abundance.
                      Prorocentrum micans was the major contributor to the total population
                      during March and April, 1988. Chlorophytes were rarely present in Tampa
                      Bay although five species were noted during the August-September period
                      of high river flow and reduced salinity (Fig. 27). Other groups (Fig.
                      28) were minor components of the phyt oplankton community.


                      180/oo Salinity Zone


                          The seasonal cycle of pbytoplankton abundance at this salinity zone
                      is distinct from Tampa Bay and all other river stations.            Total
                      abundance at this salinity zone ranked sixth (Table 2) with an annual
                      mean of 2808.8 cell ml-1 which, as with chlorophyll, was the lowest'rank
                      for a river location.   Peaks in abundance occurred in March and July
                      (Fig. 29). The maximum in September reflects counts obtained for Tampa
                      Bay when the 180/oo salinity zone was located at this station.         No


                                                          10








                        chlorophyll data  is available for'the March date, while the July maximum
                        corresponds.- to- a slight increase in chlorophyll.           Both peaks in
                        numerical abundance correspond to increases in the population of
                        microflagellates (Fig. 30), which accounted for 94% and 88% of the total
                        populations in March and July, respectively. With the exception of'          the
                        January-March, 1988 period when diatoms contributed more than 70% of the
                        total numerical abundance, microflagellates dominated numerically at
                        this salinity zone (Fig. 30). Two short-lived diatom pulses occurred in
                        May and July, respectively (Fig. 30).         The May increase was due to
                        Ceratulina bergonii while S. costatum was the most abundant diatom in
                        July (see Fig. 25). Dinoflagellate populations increased in March-April
                        but contributed less than 4% of the total abundance (Fig. 31).              Two
                        Peridinium species, Peridinium sp. and Peridinium aciculiferum, along
                        with Prorosentrum. micans were responsible for this peak, although cell
                        counts were only in the range of 20-40 cells ml-     1.  The August-September
                        bloom of the blue-green alga, Schizothrix sp. was noted at this station
                        and accounted for 47% of the tot   al in September with populations of more
                        than 10,000 filaments ml-       1   (Fig. 26 and 30).         Populations of
                        Chlorophytes were greater and occurred more.frequently than in Tampa Bay
                        but never accounted for more than 1.2% of the total population (Fig.
                        31).   Others, such as silicoflagellates and Pyramimonas were present
                        occassionally but never contributed more than a few percent of the total
                        numerical abundance (Fig. 32).


                        12 /ob Salinity   Zone


                             The annual cycle of total phytoplankton abundance at the 120/00
                        salinity zone can be characterized as a     series of peaks that vary widely
                        in magnitude over the two week sampling interval.           From March, 1988
                        through June, there is little correspondance with the annual chlorophyll
                        cycle (compare Figs. 18 and 33).        Following the July peak of maximum
                        abundance however, the fluctuating cycle is reflected in chlorophyll
                        concentration.    This July maximum can be attributed to a bloom of an
                        unknown    naked   dinoflagellate     which,   unfortunately,     burst    upon
                        preservation and   could not be. identified although it contributed 26.5%
                        of the total cell   numerical abundance (Fig. 35).











                          Microf lagellates dominated this station numerically throughout the
                     year (Fig. @4) -with the exception of the October 11 sampling date.    In
                     September, Schizothrix sp. was the numerical dominant (Figs. 26 and 35)
                     while populations of three diatom species, S. costatum, Chaetoceros
                     subtilus and Leptocylindrus minimus, combined to account for 60% of the
                     total abundance on October 11 (Figs. 25 and 34). However, this October
                     increase was not characteristic of this station where diatom populations
                     contributed less than 30% of the total community abundance during the
                     annual cycle.  Chlorophytes increased in their frequency of occurrance
                     (Fig. 36) but were also a minor component of the community. The maximum
                     in Chlorophytes as a fraction of the total population that occurred in
                     early March was the result of 6 species being present. The phagotrophic
                     Euglenoid flagellate, Eutreptia sp. was the dominant chloropbyte on that
                     date with populations of 28 cells ml- 1.                                       1
                          Total numerical abundance at this salinity zone ranked fifth lowest
                     of the six stations sampled with an annual average of 3260.8 cells ml-  1
                     (Table 2).


                     60/oo Salinity Zone


                          Sampling at. this station for cell counts began in April. However,
                     the April 6 sample was not counted in request for a bottom sample count
                     at 120/oo and the April 20 samples from all stations were lost as a
                     result of incomplete preservation.     Therefore the annual cycle of
                     phytoplankton abundance for this salinity zone begins in May, 1988.
                          The general trends of total numerical abundance (Fig. 37) resemble
                     the annual chlorophyll cycle (Fig. 19) with a maximum in May, lower
                     population density during late summer (August-September) and a series of
                     peaks in October, November, and January, 1989. Two diatoms, S. costatum
                     and S. costatum combined with Thalassiosira pseudonana were the primary
                     diatom species responsible for the October and December peaks,
                     respectively (Fig. 38 and 39), although the cell count for the December
                                                    -1
                     peak was less than 1000 cell ml . However, microflagellate populations
                     were the numerical dominants throughout most of the year at this
                     salinity zone (Fig. 38).     Peridinium aciculiferum, was the species
                     responsible for the increased dinoflagellate contribution to the



                                                         12











                       community during June and July (Fig. 40).     Schizothrix was also found
                       at this salinity zone with a population maximum at the end of September
                       (Fig. @ 40 and 41), but represented a lower percentage o     f the total
                       abundance than at higher salinity zones. On September 8 this salinity
                       zone was located just outside the mouth of the river but by the next
                       sample date, September 22, it was located 4.1 miles upstream (Table 1) .
                       Schizothrix was first found on September 8 followed by a population
                       increase on September 22. The seed population could have been entrained
                       in this lower salinity water and with subsequent growth between
                       .September 8 and 22, produced, the elevated population..      Alternately,
                       since the bloom started in Tampa Bay following the major salinity
                       reduction in August, and it was found at all higher salinity zones,
                       entrainment from Tampa Bay by tidal mixing is more likely.
                            Fresh -water species of chlorophytes showed an increased frequency
                       of occurrance at this salinity zone although their contribution to the
                       total community abundance was still less than 2.5% (Fig. 42). Peaks in
                       their percent contribution to the total community in May and mid-June
                       were due to two different Scenedesmus species, while a mixture of 6
                       species contributed to the August peak.       Akistrodesmus falcatus was
                       responsible for the October maximum and Euglenoid flagellates were
                       prevalent in December-January, 1989.      Transport of these freshwater
                       species from upstream regions probably occurred.      Although they were
                       identified in preserved samples, they had the appearance of being live
                       cells at the time of collection. The annual average was 4314 cells ml
                       at this salinity zone ranked fourth in total abundance.


                       00/oo Salinity Zone


                            Generally, the ' annual cycles of total phytoplankton numerical
                       abundance and chlorophyll concentration showed similar trends at this
                       fresh-water station (Figs. 43 and 21). There is a relative consistency
                       in total numbers throughout the year with a major bloom during the first
                       sampling in October which corresponds to elevated populations of the
                       diatom S. costatum (population density greater than 30,000 cells ml
                       Fig. 39).   Populations of two Cyclotella spp. were  wresponsible for the
                       continued dominance of diatoms during the second October sample (Fig.


                                                            13











                      44) which coincided with the chlorophyll maximum no        ted on that date
                      (Fig. 21). -'Microflagellates represented a greater proportion of the
                      community from March through September    and either co-dominated or showed
                      an inverse relationship with diatom abundance at other times (Fig. 44).
                            Chlorophytes represented a greater percentage of the total
                      population at this fresh-water station than at all other stations with a
                      maximum of approximately 7% in late September (Fig. 45). Populations of
                      Akistrodesmus, at 40 to 50 cells ml-          1,  were the most abundant
                      representatives of the Chlorophyta on this sampling date.                  The
                      blue-green algae  , Schizothrix sp., did not penetrate to this salinity
                      zone. Blue-green algae (e.g. Merismopedia sp.) were relatively rare but
                      always present (Fig. 45). other groups (Fig. 46) made up less than 1%
                      of the total phytoplankton community. Despite the major October bloom
                      with population levels of greater than 35,000 cells ml-        1, the annual
                      average for this station was 4712.1 cells ml-    I which ranked third among
                      the six stations (Table 2).



                      Ruskin Inlet



                            The annual cycle of abundance at Ruskin Inlet closely resembles
                      that of Oo/oo with a relative consistency in total numbers throughout
                      the year and a major peak in abundance in early October (Fig. 47). The
                      cycle of abundance did not entirely reflect the seasonal cycle in
                      chlorophyll concentration (see Fig. 20). Maximum abundance occurred on
                      .October 11 whereas the chlorophyll maximum occurred on November 7.
                      Other chlorophyll peaks in February and April are mirrored by cell
                      counts but the July chlorophyll peak occurs one sample date after a peak
                      in    abundance.    No   good   explanation   can   be   offered   for    this
                      dissimilarity.


                                                        1
                            The annual average. of total phytoplankton was the highest of all
                      stations at 9391.1 cells ml        ,  almost double that noted for the
                      fresh-water station and 3-fold greater than at 180/00 (Table 2).
                      Microflagellates and diatoms show a complex seasonal pattern of
                      numerical dominance with inverse shifts at about monthly intervals (Fig.
                      48).





                                                             14











                           Skeletonema costatum occurred   throughout the year at this station
                       and -was re-sponsible for the October maximum with populations that
                       exceeded 80,000 cells ml- 1  (Figs. 39 -and 48).  This species, combined
                       with a small unidentified Thalassiosira species, was responsible for the
                       continued numerical , dominance of diatoms through November (Fig. 48).
                       The S. costatum bloom on October 11 did not coincide with the annual

                       chlorophyll maximum on November 7.       Although S. costatum was the
                       numerical dominant on November 7, its' population density had decreased
                       to 12,000 cells ml -1    This S. costatum bloom did not, coincide with
                       August-October Schizotbrix bloom in Tampa Bay.      This blue-green alga
                       occurredin Ruskin Inlet from August through September (Figs. 41 and 50)
                       but was reduced to trace population levels at the time of the S.

                       costatum bloom.
                           Of particular interest is the almost. continuous presence of
                       chlorophyte-populations, especially the Euglenoid flagellates, Eutreptia
                       and Euglena spp. which are phagotrophic and associated with high organic
                       particle loads.  These two genera contributed approximately 20% of the
                       total abundance during January, 1988, July, and January, 1989 (Figs. 49
                       and 52).    Similarly, dinoflagellate populations were continuously
                       present in Ruskin Inlet, although at low population levels.             The
                       dinoflagellate bloom,in early Febuary, which accounted for almost 8  0% of
                       the total abundance (Fig. 49) was due to a naked species which burst
                       upon preservation.    A bloom of a species which showed the same
                       characteristics upon preservation occurred at   the 120/oo salinity zone
                       in July, 1988.    The minor peak in dinoflagellate abundance in April
                       (Fig. 49) resulted from the increased abundance of Prorocentrum minimum.
                       This species was present at Ruskin Inlet and all other stations at low
                       (less than 50 cell.ml-    population levels (Figs. 53 and 54). It is a
                       known red-tide species in other areas (e.g. Chesapeake Bay) and may be
                       responsible for fish-kills.     There have been anecdotal reports        of
                       red-water In Ruskin Inlet, but our sampling program did not appear to
                       coincide with.a bloom of this species.
                            Although Schizothrix sp. was found at Ruskin Inlet during the
                       August-September blue-green bloom period (Fig. 41), it was not the
                       numerical dominant for this group during the August peak noted in Fig.
                       50.  Merismopedia punctata was the major contributor in August, while


                                                            15











                       Sc hizothrix and Nostoc sp. (trichomes) combined to contribute 4% of the
                       total populittion density in September.         The population density of
                       Schizothrix at Ruskin Inlet was considerably lower than at any other
                       River salinity zone (compare Figs. 26 and 41). Although the presence of
                       this species suggests that transport from- Tampa Bay occurred, the low
                       population levels indicate that competition from other species or
                       environmental conditions were not favorable for growth.


                       Phytoplankton community composition in relation to salinity


                            Variation in the phytoplankton community composition, as indicated
                       by changes in the contribution made by several groups to the total
                       abundance, at the various fixed stations and salinity zones of the LMR
                       for each sampl   ing date is depicted in Figs. 55 to 79.               Several
                       generalities are evident.      Diatoms and microflagellates contribute a
                       greater percentage of the total phytoplankton abundance throughout the
                       year than  all other groups combined. The only exception to the dominance
                       of these  two groups occurred during September, 1988 at all locations
                       except 00/oo when the Schizothrix bloom occurred in Tampa Bay and the
                       LMR.   Microflagellates become increasingly important at all river
                       stations in spring and are the numerical dominants throughout the
                       summer, and with the exception of one or two stations on varying        sample
                       days, they are the numerically dominant group during the August-October

                       Schizothrix bloom.

                            it is difficult to discern a consistent pattern in total
                       phytoplankton counts from Tampa Bay up-river to zero salinity (Figs.
                       80,81), although the average total counts for each station and salinity
                       zone (Table 2) suggest a. trend with highest populations in the Bay,
                       reduced abundance at 180/oo and gradually increasing abundance upstream.
                       Ruskin Inlet, although it had thehighest annual mean total count is not
                       included because it is a eutrophied arm            of the river.        Diatom
                       populations were more abundant in Tampa Bay than at- any of the LMR
                       locations (Figs. 82,83) comprising an annual       average of 44.8% of the
                       total phytoplankton counts. Diatom populations varied from a minimum of
                       17.5% of the total counts at 12  0 /oo to 31.4% at  00/00. Microflagellates
                       were therefore the numerically dominant group at all river locations



                                                              16









                        with annual means that ranged from 64.,8% of the total counts at 00/oo to
                        76.1% at 12'0/oo'.  In Tampa Bay, microflagellates comprised an annual
                        average of 43.9% of the total count.        These values are reflected in
                        Figs. 84 and 85 and in Table 4 which summarizes the annual mean
                        abundance for species and groups that occurred on 13 or more sampling
                        dates. The annual mean, median and range of abundance for all species
                        identified, irregardless of location is presented.in Appendix Table 3.
                        Total counts for each major group arranged by location for each sampling
                        date are summarized in Appendix Table 4 and the same information
                        arranged by sampling date for each location. is in Appendix Table 5. The
                        combination of diatoms and microflagellates represented a range of 86.6%
                        to 96.2 % of the total phytoplankton abundance at all stations. Several
                        diatom species occurred at all stations; Skeletonema costatum, Nitzschia
                        closterium,   Nitzschia     longissima,    Thalassiosira    pseudonana     and
                        Chaetoceros subtilus (Tables 4,5 and Figs. 25,39,92 and 93).                S.
                        costatum and     the   two Nitzschia     spp. . show a broad euryhaline
                        distribution. The presence of S       cogtatum at 0  0/oo is unusual as is
                        discussed later-.   Chaetoceros subtilus (Figs.-92,93) however, occurred
                        more frequently at intermeadiate salinities (12 and 60/,oo, Table 5)      than
                        at  higher    salinities.     Diatoms    such   as   Chaetoceros     socialis,
                        Leptocylindrus minimus, Certaulina bergonii, Asterionella glacialis and
                        Tbalassionema nitzschoides occurred more frequently at higher salinities
                        (Table 5).
                             Although dinoflagellates (Figs. 86 and 87) were never abundant in
                        the Bay or the LMR, several species were present at all locations.
                        Prorocentrum minimum, Peridinium aciculiferum and Gymnodinium spp. were
                        found at all salinity zones (Table 5) while       Gonyaulax occurred at all
                        locations except Oo/oo. P. minimum was found most frequently in Ruskin
                        Inlet and Tampa Bay (Table 5) although the        highest populations were
                        found *in Ruskin Inlet (Figs. 53 and 54).         P. aciculiferum occurred
                        within the river and Ruskin Inlet with greater frequency than Tampa Bay
                        (Table 5) suggesting a preference for low to intermediate salinities.
                             The seasonal abundance of blue-green algae is governed more by the
                        August-October Schizothrix bloom than by salinity (see Figs. 26,41 and
                        88.,89). As noted above, the August and September maxima were the result'



                                                                17











                      of a bloom of this species. Only one species, Nostoc sp., occurred at
                      all location.-(Table 5) but only for a limited period.
                          Chlorophytes, as one might expect, occurred more frequently at the
                      lower salinity zones (Table 5, Figs. 90,91).      Scenedesmus quadracauda
                      and Schroederia setigera were occassionaly found in Tampa Bay after
                      periods of elevated river flow.     Eutreptia spp. and other euglenoids
                      were most common in Ruskin Inlet (see Figs. 51,52, Tables 4,5). These
                      species are indicators of organic rich areas and are associated with
                      eutrophication. They rarely occurred at other locations.


                      Similarity Index


                           This index is based on the presence or absence of a species in the
                      combined replicate counts  for each station. The community in Tampa Bay
                      for any given sampling date was compared to all LMR stations (Table 6).
                      Although there is considerable seasonal variation in similarity at a
                      given station, the general trend is for a decrease in the annual average
                      similarity from the mouth to the head of the river.     The fact that 20%
                      of the species found in Tampa Bay also occurred at 00/oo salinity with a
                      fair degree of consistentcy indicates the euryhaline nature of the
                      community in Tampa Bay and suggests that transport of Bay water with
                      accompanying cells to the head of the river occurs regularly. Although
                      34 of the 204 species or groups identified were found at 0  0/oo and Tampa
                      Bay (see Table   5), most were blue-greens and chlorophytes; species
                      characteristic   of  fresh water     habitats.   tstuarine   diatoms    and

                      dinoflagellates  such as N. closterium, N. longissima, S. costatum, C.
                      subtilus and P.  minimum, which are commonly found at higher salinities,
                      occurred at the  freshwater location which suggests up-river transport.
                           Ruskin Inlet displays  as much similarity with Tampa Bay as does the
                      120/oa salinity zone with   an annual averag e of 0.36.   The salinity at
                      Ruskin Inlet varied considerably throughout the annual cycle (Fig. 4).
                      Similarity index values averaged greater than 0.3 at Ruskin Inlet when
                      salinity was greater than 110/oo; which also emphasizes the euryhaline
                      nature of the phytoplankton community.






                                                           18..











                        Diversity Index


                             The Shannon-Weaver diversity index       is a measure of the species
                        richness (number of species) and the proportion of the total community
                        that species   represents.   Therefore, it can also be viewed as an index
                        of the eveness of distribution of populations within a community.            Low
                        values will be calculated if few species are'present or if a few         species
                        contribute the bulk of the          total population abundance,       i.e.,    a
                        relatively monospecific bloom.
                             The seasonal variation in diversity is        high at   all stations and
                        exhibits, a wide range (from 0.0 at Tampa Bay on June 15 when only one
                        species was identified to genus to -4.599 in Ruskin Inlet on August 10,
                        Table 7). The annual means indicate increasing diversity and eveness of
                        distribution among species in the upstream direction.            However, the
                        annual.variability at each river station suggests,that there would be no
                        significant difference between the annual means for each river station.
                        The annual means for both Tampa Bay and Ruskin Inlet are lower than for
                        the other river stations which reflect the periodic blooms dominated by
                        one or two species that occur at these two stations. Although both have
                        high species richness (i.e. a high number of species present) , the
                        dominance in the community by one or two'species, with others present In
                        low relative abundance, yields a low Shannon-Weaver index.



                        Cell Volume and Cell Surface Area



                              Cell size measurements were made on a total of 43 species which
                        could be approximated by geometric shapes from which volume and surface
                        area  could be calculated. An average cell size, based on measurements
                        of the same species from different sampling dates, was used in. all
                        calculations of total cell volume and surface area. Although cell size
                        for a given species did vary between samples, the variation was small
                        relative to differences in total abundance. Since the objective of this
                        part of the study was to determine if the numerical dominant also
                        dominated I th e community with respect to cell volume and surface area,
                        parameters which have ecological and physiological relevance, the
                        average cell size was used in all calculations.



                                                                19












                            Total cell volume and total cell surface area for all available
                       species is -presented in a table in Appendix 1.        Since data were not
                       available for all species counted at each station, total cell volume and
                       surface area could not be calculated. Therefore, since microflagellates
                       and the diatom, Skeletonema. costatum, were the numerical dominants at
                     .essentially all stations for most of the year (see Table 4 and Appendix
                       1), they were chosen to highlight the annual cycle of cell volume (see
                       Figs. 94 to 105).
                            In Tampa Bay (Figs. 94,95), microflagellates and S. costratum
                       co-occurred on 20 of 26 sampling dates.            Total cell volume for
                       microflagellates was greater than for S. costatum. on only two of those
                       dates (April 6 and June 29).        On April 6, the diatoms Chaetoceros
                       neogracile and Ceratulina bergonii and several minor species dominated
                       the community with respect to cell volume (3,170,283 um      3     Similarly,
                       on June 29, the diatom Thalassionema. nitzschoides was both the numerical
                       and cell volume dominant (17,474,836 um  3 ).
                            At 180/oo, microflagellates and 9. costatum, co-occurred on 20 of 26
                       sampling dates with microflagellate cell volume greater than.S. costatum
                       on 4 dates (Appendix 1). However, with the exception of the December 8
                       sampling   date,    total   diatom    cell    volume   was    greater     than
                       microflagellates (Figs. 96,97).     The same result was obtained for the
                       120/oo station (see Figs. 98,99; Appendix 1) with May 18 being the only
                       date when microflagellates dominated numerically and by cell volume.
                            S. costatum and microf lagel late s co-occurred on 19 sampling dates
                       at the 60/oo salinity zone with 9 dates when microflagellate cell volume
                       was greater then S. costatum      (Figs. 100,101).   As at other stations,
                       total diatom cell volume reduced the times when microflagellates
                       dominated numerically and volumetrically to 3.        Although the overall
                       abundance of microflagellates was greater at Ruskin Inlet than at any
                       other IMR station, this group was never dominant with respect to cell
                       volume (Figs. 102,103).     At Oo/oo, microflagellaites and S. costatum
                       co-occurred on 18 of 26 sampling dates yet flagellates dominated
                       volumetrically on only one of those dates (see Figs. 104,105). However,
                       there is a question of the viability of S. costatum. at this location.
                       Cells always had a dense appearance without distinct chloroplasts and
                       the intracellular space was much reduced. A definitive determination of



                                                             20










                       viability cannot be made, so  for the purpose of this study we will only
                       report this--species presence and contribution to the community with no
                       assumption of viability.



                       PRODUCTION AND NUTRIENT ADDITION EXPERIMENTS


                       Voiumetric Production Rates (mgC M-3   hr- 1) and Productivity Index (mgC
                       mgChl-1 hr-


                           Volumetric productivity and    the productivity index (PI) are based
                       on the ON,OP replicate samples incubated at approximately 300 uE m   -2  s-1
                       at the temperature at which samples were collected. . The irradiance
                       value  was   chosen    to   yield   maximum   production   rates    without
                       photoinhibition responses. With a surface irradiance of 1900 uE M-2      a-1
                       this value is approximately 16% of the surface intensity. Based on the
                       annual average extinction coefficients (Table 2), an irradiance of 300
                       uE m_2 s-I would be found between Min and 1.6m at the 0     0/oo and Tampa
                       Bay stations, respectively. It should, therefore be close to an average
                       water column. irradiance.   Since light was constant for all sampling
                       dates, productivity and the PI should only vary with temperature,
                       biomass or nutrient availability.


                       Tampa Bay


                            Volumetric production rates in Tampa Bay were generally low
                                                                                 -3    -1
                       throughout the Fall and Spring with values of 50 mgC m        hr   or less
                       (Fig. 106). From June through August, production increased dramatically
                       with elevated rates all greater than 100 mgC M-3    hr- 1.  The maximum in
                       early June corresponds to a period of low cell counts (see Fig. 23) with
                       microflagellates numerically dominant (see Fig. 24) and minor diatom
                       populations. Chlorophyll concentrations were elevated from the previous
                       sample date (see Fig. 16).       The annual minimum    occurred in early
                       September during the period of maximum river flow (Fig. 2). The peak
                       that occurred on the last sample date in September is displaced by one
                       sample period from the October chlorophyll maximum but occurs when the
                       community was dominated by the blue-green alga, Schizothrix. The annual



                                                            21








                     average for production at the Tampa Bay station was 89.88 mgC m_3      hr-I
                     whic h ranked-second of 4 stations (Table 2).
                          The PI displays considerable seasonal variation, with values that
                     range from less than I to greater than 20 (Fig. 107).        Lowest values
                     occur during April and May when cell counts were low and chlorophyll
                     concentrations were highly variable.        Microflagellates numerically
                     dominated the community with diatoms comprising less than 20% of the
                     total abundance.   However, for the remainder of the year, the PI was
                     greater than 5 which can be considered indicative of nutrient replete
                     populations (Curl and Small, 1965, Eppley et al., 1973, Eppley, 1981).
                     From September through January, 1989, the PI was relatively constant
                     despite wide variations in chlorophyll and total abundance.


                     180/oo Salinity Zone


                          Volumetric production rates at this salinity zone were relatively
                     constant throughout the year (Fig. 106).     Rates were always less than
                               -3   -1
                     100 mgC m    hr   with an annual minimum during the September period of
                     high river flow.    In September and October, when the 180/oo salinity
                     zone was located  in Tampa Bay, production rates for the Bay were assumed
                     to be equivalent  to 180/00.
                           The consistency of production rates at this station correspond to


                                                                                 3    1
                     its low ranking in total population abundance and chlorophyll
                     concentration.   With an annual average of 50.89 mgC m        hr    it was
                     again the lowest ranked station (Table 2).
                          However, populations at this station displayed the highest PI (see
                     Table 1) which also showed a high degree of consistency (Fig. 107)
                     despite a four-fold variation in chlorophyll concentration and wide
                     fluctuation in total abundance.     All PI values at this salinity zone
                     were above -5, with the majority above 10, which is indicative of
                     nutrient sufficient populations.


                     120/oo Salinity Zone


                          As at 18 0/oo, the annual cycle at this salinity zone displays less
                     variation than in Tampa Bay with volumetric production rates generally



                                                          22













                                             -3
                        less than 100 mgC m     hr-' (Fig. 108). However values greater than 100
                        occur f rom -@June through early August.     The maximum occurs during the
                        first sample in July and corresponds to the chlorophyll maximum and the
                        maximum in total abundance. There is no general relationship with total
                        abundance, however, since this station displayed the greatest sample to
                        sample variation of any location (see Fig. 33).
                              The PI is essentially constant throughout the year at approximately
                        10 mgC mgCh1      hr      The essentially constant PI for this station
                        suggests that production was strictly a function of biomass with no
                        nutrient limitation#


                        00/oo Salinity Zone


                              Volumetric production rates at this salinity zone'display a high
                        degree of annual variation (Fig.108) reflecting a similar degree of
                        variability in chlorophyll concentration (see Fig. 21).             Decreasing
                        production during July, August and September reflects low cell counts
                        (see Fig. 43), low chlorophyll 'concentrations and Increasing stream
                        flow.   The October production maximum corresponds to the chlorophyll.
                        maximum.and a diatom bloom of the genus Cyclotella.
                              The' PI displays the same consistency- noted for the previous
                        salinity zone (Fig. 109) although values are lower during fall and
                        winter.    The maximum value of 17' occurred on September 22, when
                        chlorophyll and cell counts were low and microflagellates contributed
                        80% of the total abundance.
                              This salinity zone had the highest mean annual production rate
                        (122.25 mgC M-3   hr-') but ranked lowest with a PI of 8.79 mgC mgCbl_
                        hr-1  (Table 2).


                        Effects    of   Nitrogen    and    Phosphorus    Additions    on    Short-term
                        Photosynthesis


                              Potential  nutrient limitation of short-term p    hotosynthesis (3 hr.
                        incubations) and potential nitrogen limitation of the community was
                        assessed in two ways: 1. Nitrate and phosphate alone and in combination
                        were added to  replicate bottles incubated in the light at.300 uE m     -2 s -1


                                                               23











                      to assess if stimulation, inhibition or no effect occurred during
                      photosynthesis and, 2. An ammonium addition was made to replicate dark
                      bottles to determine the effect on carbon-14 uptake in the dark. The
                      latter effect was assessed by calculating the ratio of CPM (counts per
                      minute) in the dark bottles (D) with (+) and without (-) ammonium and by
                      calculating the actual production rate in the ammonium addition bottles
                      over and above the standard dark bottle correction (Table 8; D+/D-
                                                   3     1
                      CPM/CPM; VD+ - V D- = mgC m- hr-        Addition of ammonium to nitrogen
                      limited populations should enhance  dark carbon-14 uptake (Morris et al.,
                      1971; Elrifi and Turpin, 1987).
                           The effect of nitrate and phosphorus additions on photosynthesis is
                      shown in Figs. 110 to 121 for the four stations at which carbon-14
                      uptake measurements were made.      The results are expressed as the
                      difference in the average photosynthesis rates between the bottles
                      receiving a nutrient addition and those receiving no addition (ON, OP).
                      Thus a positive value indicates an enhancement of photosynthesis as a
                      result of the nutrient addition while a negative value indicates
                      inhibition.    The productivity    index   rather than     the volumetric
                      production rate was used since the differences will be smaller numbers
                      which reduces the range of values used in the plots.            Since all
                      photosynthesis measurements were. only done in duplicate, statistical
                      analyses were not performed. However, if the difference between the PI
                      index for any nutrient addition and the index for ONOP was equal to or
                      greater than 2, the range of each replicate was examined. If the range
                      for each treatment overlapped, then I inferred there was no difference

                      between treatments.

                           Additions of    nitrate   and   phosphate   had   little   effect    on
                      photosynthesis at any station.     Differences between samples with and
                      without nutrient additions were generally less than 2.          There were
                      however some specific sampling dates at each station where the ranges of
                      the paired bottles did not overlap.       For example, in Tampa Bay the
                      addition of nitrate alone reduced photosynthesis in the July 28 sample
                      (Fig. 110), while the addition of phosphate alone or in combination had
                      no effect (Figs. 111,112). Although there appears to be an enhancement
                      of photosynthesis by the addition of nitrate and phosphate to the June
                      15 sample (Fig. 110), the ranges of both sets of replicates overlapped


                                                           24











                       considerably.  Phosphate alone reduced photosynthesis in the Feb. 10
                       sample (Fig, 111), but no other effect was noted.,        The addition of
                       nitrate and phosphate in combination produced a trend for reduction in
                       photosynthesis throughout the y  ear (Fig. 112), however, none of the
                       differences were significant.
                            At 180/oo the addition of nitrate enhanced photosynthesis only in
                       the July 14 sample (Fig. 113), whereas    the.addition of phosphate alone
                       and in combination with nitrate enhanced carbon-14 uptake in samples
                       from June 29 through August 10 (Figs. 114,115).         This is somewhat
                       enigmatic since phosphate concentrations at this station were always
                       pr esent in excess with concentrations never less than 45 ug 1  -1  (4.7 ug

                       at
                            The degree of stimulation/ reduction in samples from the 12 O/oo
                       salinity zone showed a mixed seasonal response.          Nitrate addition
                       yielded a significant enchancement only in the January 24, 1989 sample
                       (Fig. 116). Phosphate additions enhanced photosynthesis in March, July
                       and January, 1989 while causing a significant reduction in August (Fig.
                       117). When added in combination with nitrate,     phosphate only enhanced
                       photosynthesis in October (Fig. 118).
                            At 0 O/oo, the addition of nitrate alonei phosphate alone and in
                       combination reduced photosynthesis significantly on only two dates,
                       April 18 and August 30 (Figs. 119,120,121). Neither inorganic nitrogen
                       or phosphorus concentrations were depleted in the water column on either
                       date and the August sample coincided with minimum chlorophyll
                       concentrations and low numerical abundance.

                            Ammonium additions enhanced dark carbon-14 uptake on a majority of
                       sampling dates at all stations based on the calculation of V      D+ - V  D-
                       (Figs. 122 to 125)    However, the ratio of D+/D- exceeded 2 only on 2
                       occasions (July 128 at 180/oo and April 18 at 120/oo, Table 4) with
                       almost all values falling in the range of 1 to 2. Therefore the degree
                       of enhanced dark carbon-14 uptake following nitrogen addition must be
                       considered as a trend indicative of nutrient. sufficient to borderline

                       nitrogen limitation.








                                                            25













                     DISC USSION



                     Community composition and abundance


                          The phytoplankton community in the Little Manatee River and at   the
                     Tampa Bay station consists of a seasonally varying mixture of
                     representative species of diatoms, dinoflagellates, microflagellates and
                     chlorophytes with a sporatic occurrance of blue-green algae. A total of
                     91 taxa of diatoms (some only to genera), 35 dinoflagellate taxa, 57
                     chlorophytes, 6 blue-green alga genera, 3 silicoflagellates and several
                     representatives of other diverse microalgal groups were identified and
                     @counted. Microflagellates, which consisted of a diverse group of
                     unidentified species, were not identified to a specific taxon but were
                     counted as-a group. The number of taxa are comparable to the extensive
                     list of phytoplankton summarized by Steidinger and Gardiner (1985, see
                     their Table 1). Similarly, total abundance at the LMR Tampa Bay station
                     is comparable to that reported by the City of Tampa (COT, 1981) for
                     their Station 13 in mid-Tampa Bay and exhibits a similar seasonal cycle
                     with lower population density during March, April and May and a series
                     of blooms throughout the summer, fall and winter. Seasonal average cell
                     counts for the LMR reported by Turner and Hopkins (1974) are lower than
                     the annual averages calculated for this study (Table 2). However, their
                     station locations appear to have been near the mouth of the river which
                     had the lowest average total abundance. Differences in counting methods
                     must also be taken into account and perhaps more importantly, there is
                     no information available on inter-annual variability for the LMR.
                          Seasonal phytoplankton community dynamics in the LMR and at the
                     Tampa Bay station. can be characterized as exhibiting a series of
                     re-occurring blooms with a semi-monthly to monthly frequency. With the
                     exception of the period of increased river flow in August-September and
                     the Schizothrix bloom in Tampa Bay which invaded the river, there is no
                     distinct seasonal pattern of abundance common to all-river locations.
                     However, populations of several species and groups displayed a
                     seasonality in abundance and,dominance that occurred at the Tampa Bay
                     station and all river locations suggesting a linkage between the river
                     and Tampa Bay.



                                                         26











                             The ubiquitous diatom, Skeletonema costatum, can be considered the
                        dominant species during the entire year in the LMR and Tampa Bay.               It
                        was an important component (both numerically and as cell volume) of
                        blooms at all stations.       Steidinger and Gardiner (1985 and references
                        therein) and Turner and Hopkins @1974) also described this species as
                        the dominant in the entire Tampa Bay system.           Blooms of other diatom
                        species    (e.g.    Ceratulina     bergonii,    Thalassionema       nitzschoides)
                        contributed substantially to the community during summer blooms at
                        salinity zones greater than 120/oo.            Several Cbaetoceros spp.        (C.
                        subtilus, C. socialis and C. neogracile) were almost always present in
                        all salinity zones and contributed to the dominance of diatom
                        populations with respect to total- cell volume (see Appendix 1).
                        Microflagellates, which includes picoplankton sized cells (0.2 to 2.Oum)
                        were numerically dominant in. Tampa Bay during spring and fall and in
                        Ruskin Inlet during spring and summer.           However, this group was the
                        numerical dominant at all other LMR stations for most of the year. This
                        was particulary true for the 12            and 6  0/oo salinity zones where
                        microflagellate populations contributed 76.1% and 65.3% of the total
                        phytoplankton abundance, respecitively.         Diatoms contributed 31.4% of
                                                      0
                        the total abundance at 0 /oo which contrasts with the intermediate
                        salinity ranges where diatom abundance decreased (27.2% at 18        0/oo, 17.5%
                        at 12 0 /oo, and 21.3% at 60/oo). -Similar results for Tampa Bay were
                        reported by Dragovich and Kelly (1964) and summarized by Steidinger*and
                        Gardiner (1985).     In estuaries, coastal and oceanic waters this group
                        can contribute 30    to 90% of the biomass and primary production (Malone,
                        1977, 1980; Durbin et al., 1975; Takahashi and Bienfang, 1983, Stockner,
                        1988).    Although   numerically important in        the LMR and Tampa Bay,
                        microflagellates did not dominate with respect to cell volume. Nutrient
                        uptake rates and     growth rates (to a limited      extent, Banse, 1982) are
                        cell size dependent and water column production has been related to cell
                        volume and surface area (Smayda, 1965, Paascbe, 1960).               Measurements
                        required    to evaluate the role of micro f lagel lates in the LMR
                        phyto plankton community at the functional and process level have not
                        been made, nor is there information available on their contribution to
                        food web dynamics in the LMR system. Such information must be obtained
                        for a complete evaluation of this group in the phytoplankton community
                        dynamics of the Tampa Bay sy    st em.

                                                                 27











                          The number of taxa recorded during this study suggests a high
                      degree of species richness or diversity in the phytoplankton community.
                      Calculations of diversity (Table 7), however, yield annual averages that
                      range from 1.231 to 1.833. Margalef (1968) indicates values of 2.5 are
                      common for actively growing coastal phytoplankton populations, 3.5 to
                      4.0 in the latter stages of succession and less than 2.5 for estuaries
                      while ranges of I to 2.5 occur in eutrophic lakes.         Ignatiades and
                      Mimicos (1977) derived values of 3.15 and 2.37 for unpolluted and
                      polluted coastal waters respectively.    Similarly, indices in the range
                      of 0.4 to 2.6 with an annual mean of 1.7 were calculated for the highly
                      polluted Newark Bay, N.J. (McCormick   and Quinn, 1975). Values for the
                      LMR and Tampa Bay are within the same range   as found in Newark Bay with
                      annual averages of approximately 1.7. McCormick and Quinn (1975) used
                      the same calculation of diversity as in this report and used Genus as
                      the lowest taxonomic criterium.      Therefore the Newark Bay and LMR
                      diversity estimates are entirely comparable. Low diversity indices and
                      high annual average biomass are indicative of an eutrophic estuary.
                      Elevated nutrient levels, particularly phosphate, silicate and ammonium,
                      are also indicative of    an enriched estuary.     The lack of nutrient
                      limitation of short-term photosynthesis (discussed below) suggests
                      nutrients were not limiting photosynthesis and were sufficient to
                      support the phytoplankton standing crop.
                           Eutrophication within the LMR is, however, a matter of degree.
                      Stations at 00/oo and Ruskin Inlet, with elevated biomass, cell counts
                      and production (00/oo) are at one end of the spectrum, while the 180/oo
                      salinity zone was at the other.      This latter station had the lowest
                      total abundance, chlorophyll concentration, production and highest PI in
                      the river (Table 2); characteristics which are not indicative of
                      eutrophication. Annual mean values for ammonium and phosphate at Ruskin
                      Inlet, 180/oo and 12 O/oo were 0.072 and 0.351, 0.088 and 0.333, 0.087
                      and 0.324 mg 1     respectively. Silicate concentrations were higher at
                      Ruskin Inlet and 12 O/oo than at 180/oo (3.54, 3.03 and 2.21 mg 1-
                      respectively), but this element was always available in excess.       Since
                      the average extinction coefficient at 18  0/oo yields a 1% light level of
                      3.9 meters, well below the average bottom depth for this salinity zone,
                      factors other than light or nutrients must be governing phytoplankton


                                                           28










                        abundance and production. Although the conclusion regarding the LMR as
                        a eutrophic --system may not apply directly to the 180/oo salinity zone,
                        excess nutrient availability and its diversity index-does not exclude

                        it.
                             Several other points regarding species composition in the LMR and
                        Tampa Bay are of       interest.   Transport    of  the blue-green alga,
                        Schizothrix, which invaded the river from Tampa Bay, the presence of
                        Skeletonema costatum at the 00/oo station and the annual average of 20%
                        of Bay species at 0   0/oo (Table 6) indicates significant interaction
                        between the mouth and head of the river.          Transport of freshwater
                        species to Tampa Bay also occurred but, as noted above (see Similarity
                        Index section),  the presence of several species of estuarine diatoms,
                        commonly found in Tampa Bay suggests upstream transport does occur.
                        Although the S. costatum. bloom in October at the fresh water station
                        coincided with a bloom at all other stations and Tampa Bay, and there is
                        a question about the viability of this species at this low salinity, its
                        presence is relevant to any future studies or models of carbon flux and
                        trop.hic interactions in the LMR.
                             Phytoplankton biomass, as indicated by chlorophyll levels, is
                        primarily a product of growth in the river system.               Chlorophyll
                        concentrations at the Wimauma station (see Fig. 22), which is upstream
                        from all LMR salinity zones, were considerably lower than the 00/00
                        salinity zone and all other regions of the LMR.        Therefore, elevated
                        biomass in the LMR is the result of growth within the river system.
                             The eutrophic character of Ruskin Inlet is further emphasized by
                        the almost year-round presence of two motile Chlorophytes, Eutreptia sp.
                        and Euglena sp.. Both genera are phagotrophic and are associated with
                        areas of high organic pollution (S. Wicks'. pers. comm.).           Attention
                        should also be paid to the presence of Prorocentrum minimum as a member
                        of the community in Ruskin      Inlet.   This species is responsible      for
                        massive red-tide blooms in other areas (e.g. Chesapeake Bay: Tyler and
                        Seliger, 19 81) and is euryhaline and eurythermal.
                             Another species of interest is the chain forming pennate diatom,
                        Nitzschia pungens. This species was.a significant component of the July
                        28 bloom in Tampa Bay and occurred at all other stations except 00/00.
                        It is now known to produce domoic acid, a toxic excitory amino acid,



                                                              29











                       which has recently been implicated as the causative agent of Amnesic
                       Shellfish Poisoning. Over 100 people from Prince Edward Island, Canada
                       became intoxicated. with symptoms that, in their advanced stage, cause
                       memory loss (Smith et al., 1989; Subba Rao and deFritas, 1989 and Todd
                       1989).   Little information is available about the quantity of toxin
                       produced, clonal variation or the population levels necessary to cause
                       shellfish toxicity.


                       Nutrient addition experiments


                            The use of short-term photosynthesis measurements with nutrient
                       additions as a measure of potential nutrient limitation has been
                       summarized by Elrifi and Turpin (1987) for nitrogen and by Lean and Pick
                       (1981) for phosphorus in fresh waters. In     both cases, photosynthesis is
                       reduced over the short-term as a result of competition for available
                       carbon skeletons and directing available energy to nutrient uptake when
                       cells are nutrient limited.      This reduction in carbon-14 uptake was
                       measured in the first tens of minutes to 2-3 hours by Elrifi and Turpin
                       (1987) after the addition of nitrate, nitrite or ammonium         to nitrogen
                       deficient cells and within the first 3 hours for phosphorus additions to
                       cultures and natural populations of freshwater phytoplankton (Lean and
                       Pick, 1981). Uptake rates of N or P by nitrogen and phosphorus limited
                       cells in the light are enhanced relative to nutrient sufficient cells
                       (see Morris, 1980 and Harris, 1986), which, over the long term (24 hours
                       or longer), results in enhanced photosynthesis and biomass proportional
                       to the concentration of the limiting nutrient.
                            Enhancement of carbon-14 uptake in the dark upon the addition of
                       ammonium was used. as an indicator of N-limItation in cultures and
                       natural populations by Morris et al. (1971) and Yentsch et al. (1977).
                       Elrifi and Turpin (1987) subsequently postulated a mechanism for this
                       enhanced CO 2  uptake in the dark and demonstrated enhancement in the
                       ratio of dark uptake with and without ammonium in cultures over a range
                       of N-limited growth.       The ratio    increased to approximately 3 in
                       populations under severe nitrogen limitation while a ratio of 1 was
                       indicative of nutrient sufficient populations.




                                                              30










                              Enrichment of samples f rom Tampa Bay and 3 'LMR            stations with
                        nitrate    and   phosphate    does   not    show   consistent    reduction     (or
                        enhancement) of photosynthesis.        There is a general trend toward a
                        reduction of photosynthesis with both N and P addition at all stations,
                        however this cannot be statistically demonstrated.             When signif icant
                        (with respect to a difference greater than 2) reduction or enhancement
                        did occur, the results were not consistent with water column nutrient

                        levels.
                              The enhancement of dark carbon-14 uptake upon the addition of
                        ammonium did yield    consistent ratios greater than 1 at all stations for
                        a majority of sampling dates. With the exception of D+/D- ratios (CPM
                        with ammonium/CPM without ammonium).greater than 2 at 18        0/oo on July 28
                        and at 12 0 /oo on May 18 (Table 8), all ratios were les       s than 2. Using
                        the results reported by Morris et al. (1971) and Elfifi and Turpin
                        (1987) as a basis for determining N-limited populations, communities in
                        Tampa Bay and the LMR could be considered nutrient sufficient or
                        borderline N-limited for short-term photosynthesis. This conclusion is
                        supported by the average annual PI, which for all locations was greater
                        than 8 (Table 2).       Values of 3 or less are generally indicative of
                        nutrient limited populations or populations from oligotrophic waters,
                        whereas values above 5 are generally indicative of nutrient replete
                        populations (Curl and Small, 1965; Malone, 1971; Eppley et al., 1973).
                        Additionally, when environmental conditions do not limit photosynthesis,
                        there should be a direct relationship between the photosynthetic rate
                        and biomass. This. relationship was examined for Tampa Bay and the LMR
                        production stations (Figs. 126 to 130). In Tampa Bay, the relationship
                                                               2
                        yield a correlation coefficient (r        of 0.64 if the two outlying points
                        'from May 4 and October 11 are deleted.. At 180/oo, 120/oo and 00/oo, the
                         .2
                        r     values are 0.59, 0.96 and 0.83,. respectively (Figs. 127,128 and
                        130).   All suggest, especially the relationships at 120/oo and 00/00,,
                        that production was governed by the biomass present with no nutrient
                        limitation.    Light was constant during the incubation periods and there
                        was no relationship between the PI and temperature (e.g. at 120/oo, Fig.
                        129). If we assume that our experiments measured something close to the
                        real P      value for the water column then, the results suggest that
                               max
                        neither     temperature     nor    nutrients     were     limiting     short-term



                                                                 31











                      photosynthesis rates in Tampa Bay or the 3 LMR salinity zones.
                                                                                          0/00
                           This c6nsistency in the PI index, especially for the 12               and
                      00/oo salinity zones, is even more remarkable given the changes in
                      community composition based on numerical abundance that occurred at

                      these and other stations. Variations in PI with both the size structure
                      and composition of phytoplankton communities are well documented (see
                      Malone, 1980a,b).     Taguchi (1976) reported that P     max  normalized to
                      chlorophyll (i.e. the PI index) decreased rapidly with cell size between
                      5 and 10 um spherical diameter and remained relatively constant for
                      species   with    diameters   between    25   and   170   um          Although
                      microflagellates were the numerical dominants at 120/oo throughout the
                      year , S. costatum or other diatoms dominated with' respect to cell
                      volume.   This Implies that the diatom populations were of primary
                      importance from a physiological and, therefore, process standpoint.
                      This remains to be tested.     Another interpretation of this consistency
                      in the PI is that all components of the community were equally efficient
                      at photosynthesis under the prevailing environmental conditions.



                      POTENTIAL FOR EUTROPHICATION IN THE LMR



                           Although     the   data    suggests    that    short-term,      potential
                      photosynthesis was not nutrient limited, this should not be taken to
                      imply that limitation of longer-term growth or biomass did not occur.
                      Discontinuous nutrient supplies, patchiness (both temporal and spatial)
                      and high uptake rates during periods of nutrient availability will allow
                      cells to fill internal storage compartments which can then be utilized
                      to maintain photosynthetic rates (see Eppley, 1981).            Coastal and
                      oceanic phytoplankton populations can exhibit photosynthetic rates,
                      uptake rates and compositional ratios. which are indicative of nutrient
                      sufficient populations (Sakshaug, 1980; Eppley, 1981) when in situ
                      nutrient levels are virtually undetectable. As long as biomass remains
                      low and relatively constant (at steady-state as in a chemostat),
                      resupply rates via remineralization processes regulate growth and
                      production (Smayda, 1983).     Increasing the rate of remineralization or
                      the absolute availability (concentration) will allow an increase in
                      growth and, therefore, biomass.         In this sense, the steady-state



                                                             32











                       population may not exhibit indications of nutrient limitation but growth

                       and biomass.would be considered as limited.

                            Examination of the water column concentrations of ammonium,
                       nitrate, total dissolved inorganic nitrogen (DIN), and phosphate (Figs.
                       131 to 154), indicates that phosphate is always present in excess while
                       ammonium, nitrate and DIN concentrations vary considerably and are at
                       times at the limits of detection in the LMR and Tampa Bay.           Ammonium
                       concentrations, however, vary widely and contribute most of the nitrogen
                       to the total DIN supply. Although there is usually measureable DIN in
                       the water column, the ratio of Nitrogen: Phosphorus (N:P) either as
                       nitrate or DIN were low with values less than 2 for most of the year in
                       the LMR and Tampa Bay.     Ratios of the same magnitude were compiled by
                       Fanning and Bell (1985) and by Turner and Hopkins (1974) for Tampa Bay
                       and its tributaries.      They also describe their relationship with
                       potential nitrogen limitation of phytoplankton communities.             Under
                       conditions of low N:P ratios, increasing the concentration of available
                       nitrogen should yield increased biomass.
                            Nitrogen additions to samples collected at the 120/oo salinity zone
                       in the LMR and Tampa Bay are being conducted as part of the second year
                       study.   Preliminary results for the first five months , are shown in
                       Appendix 2. With the exception of the      April sample in both Tampa Bay
                       and the, river, nitrogen additions yield a dramatic increase in
                       chlorophyll levels, particularly in the greater than 12 um size
                       fraction.   This size fraction is dominated by chain-forming diatoms,
                       particularly S. costatum and Chaetoceros spp.. Both can be considered
                       r-selected species (Kilham and Kilham, 1980) that can outcompete others
                       due to high nutrient unlimited growth rates. The addition of silicate
                       alone and in combination with 25 uM nitrogen does not increase yield
                       over the nitrogen addition alone (Appendix 2). High silicate levels in
                       the LMR and Tampa Bay (Figs. 155 to 160) with concomittent low N:Si
                       ratios should favor the selection of diatoms over other groups of
                       phytoplankton (Sommer, 1986; Doering et al., 1989) which will dominate
                       the community if their intrinsic growth rates are high.         If silicate
                       concentrations in the LMR were low, with concomittent low nitrogen
                       levels, then groups such as flagellates or nitrogen fixing blue-green
                       algae would have the ability to outcompete diatom populations.


                                                             33











                     Blue-greens and other nuisance algae predomina  te in lakes at N:P ratios
                     higher than--found in Tampa Bay and the LMR (Schindler, 1977; Barica et
                     al., 1980).   Therefore it is plausible to suggest that the community
                     structure in the LMR and Tampa Bay, with a dominance by diatom
                     populations and a "normal" community composition of flagellates and
                     diatoms is dependent upon the availability of silicate.
                          Increased nitrogen loading of this estuarine system will increase
                     the phytoplankton yield as our Year 2 experiments demonstrate and as the
                     low N:P ratios suggest.       The fact that this report suggests the
                     phytoplankton community     is nutrient sufficient with        respect to
                     short-term photosynthesis does not negate the previous statement.
                     Little to no growth is observed in samples receiving no nitrogen
                     addition in our current work.          Therefore, the community is at
                     steady-state with respect to in situ nutrient levels, or some other
                     environmental factor is limiting   growth. Since nitrogen addition     alone
                     Increases yield, other growth factors are not limiting. The potential
                     for increased eutrophication in the LMR and Tampa Bay is, therefore,
                     high if increased nitrogen loading occurs.































                                                           34













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                      Malone, T.C. 1980a. Algal Size. In: The Physiological Ecology of
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                      Margalef, R. 1968. Perspectives in Ecological Theory. Univ. of Chicago
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                      McCormick, J.M. and P.T. Quinn. 1975. Phytop    lankton diversity and
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                                                             36











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                       Morris, 1. 1980-. The Physiological Ecology of Phytoplankton. Univ. of
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                                                         38











                 Table I : Location of Little Manates River salinity stations and the Tampa Bay station
				   by Rivermile.  Rivermiles were measured as distance from the mouth.  Negative
				   numbers indicate distance into Tampa Bay measured in the channel from
				   navigation marker #1.  Positive numbers are distances from the mouth toward
				   the head of the river.


                 Date/Station    T. Bay      18%             12%              6%             0%          R. Inlet

                 01/26/88        -2.27*       -0.22           N.D.            N.D.          5.7          2.50*
                 02/10                        -0.31           N.D.            N.D.          6.1
                 02/24                         0.44           1.95            3.40          6.5
                 03/09                         0.00           0.83            3.00          4.65
                 03/22                        -1.82          -0.18            1.53          4.15
                 04/06                         0.00           2.55            6.00          7.2
                 04/20                         1.30           3.60            6.25          8.45
                 05/04                         1.85           3.70            6.15          8.35
                 05/18                         2.55           6.10            7.23         10.23
                 06/01                         3.70                           8.30         10.46
                 06/15                         4.80           6.60            8.60         10.45
                 06/29                         5.10           6.16            9.60         10.63
                 07/14                         3.50           5.19            8.34          9.85
                 07/28                         1.40           3.50            5.30          7.19
                 08/10                         0.00           0.34            1.15          4.24
                 08/30                        -1.23          -0.91            0.00          3.40
                 09/08                        -2.10          T.Bay            -0.81         0.0
                 09/12                        T.Bay           1.53            4.10          6.25
                 10/11                        T-Bay          -0.45            4.20          6.25
                 10/25                        -0.19           1.00            2.72          7.10
                 11/07                        -1.45          -1.18            1.40          4.55
                 11/21                        -0.37           0.95            4.70          7.83
                 12/08                        -1.46           0.80            3.80          7.19
                 12/20                         0.00           1.51            4.65          7.19
                 01/11/89                      0.00           2.70            4.44          7.6
                 01/24                        T.Bay          -1.55            0.91          4.24


                 Average          -2.27      +0.65          +2.19            +4.37        6.76         +2.50

                                                                                                          0
                 Range             0          -2.10to5.10    -1-55to6.60     -0.81to9.6     O.OtolO.63


                 *fixed location
















                                                                  39
 



                                                                                              .  I
                                       M'=''M M'Mi'M W! M tow M'M M M











                      Table 2   Annual mean values for several parameters in the LMR and Tampa Bay arranged In rank order.


                            Total Counts              Chla                Extinction Coeff.     Photos_ynthesis         P.I.
                      Rank Station     cells El-      Station pit         Station a  -1         Station       -3hr-1    Station    nRCWRCh1-  hr-

                      I     R.Inlet    9391.1         OL         18.32    Ox        -2.88       Ox         122.25       IBX        12.34

                      2     T.Bay      6007.0         R.Inlet    17.79    6X        -2.01       T.Bay       89.38       12X        11.41

                      3     Ox         4712.1         6X         13.63    R.Inlet   -1.91       12X         84.85       T.Bay      10.66

                      4     6X         4314.0         12X         9.41    MOR       -1.61       18X         50.89       Ox           8.79


                      5     12%.       3260.8         T.Bay       7.46    12X       -1.54

                      6     18%.       2808.8         18X       4.72.     18X       -1.19


                      7                                                   T.Bay     -1.15










                   Table 3    Percent of surface irradiance at the maximum depth attained during the
                              irradiance profile. Maximum depths were all within 0.5 m or less of the
                              bottom.



                   Date          T. Bay        MOR         lax          12%         6X          Ox          R. Inlet

                   01/26/88       7.5           2.5        14.5         N.D.        N.D.        0.2         0.8
                   02/10          N.D.          N.D.        N.D.        N.D.        N.D.        N.D.        N.D
                   02/24         20.0          16.5         6.8         4.0         3.5         0.1         5.7
                   03/09         17.0           N.D.       10.0         2.9         0.3         0.05        0.8
                   03/22         24.6           5.3         9.6         5.0         4.3         0.6         0.6
                   04/06          8.3           N.D.       16.7         4.8         2.1         0.8         9.8
                   04/20         13.9          10.9        12.3         3.5         9.8         14.3        7.3
                   05/04          7.6          28.8        14.5         7.2         2.3         5.4         7.5
                   05118          N.D.          N.D.        N.D.        N.D.        N.D.        N.D.        N.D.
                   06/01          2.4           7.2         6.4         1.2         2.4         N.D.        2.7
                   06/15          0.6           9.9        11.5         0.5         3.9         8.5         1.5
                   06/29          0.6          12.7         2.2         7.9         1.4         17.5        5.2
                   07/14          1.5           6.5         3.1         1.1         1.2         4.9         4.9
                   07/28          5.2          .8.2         4.8         1.3         0.3         0.02        2.7
                   08/10          4.1           N.D.        2.8         1.8         1.0         0.3         0.3
                   08/30          2.9           0.09        3.0         2.4         0.7         0.05        0.5
                   09/08          N.D.*         N.D.        N.D.        N.D.        N.D.        N.D.        N.D.
                   09/22          2.8           1.0         N.D-.**     0.4         0.4         0.04        0.1
                   10/11          2.7           4.5         N.D.**      2.9         1.6         0.6         3.9
                   10/25          5.2           N.D.        4.9         1.8         9.3         0.08        0.9
                   11/07          5.1           1.7         1.9         5.8         1.6         4.5         1.2
                   11/21          7.7          10.4         9.6         2A          4.1         0.6         2.3
                   12/08         14.3           5.7         9.6         0.4         4.7         3.4         4.4
                   12/20         11.2           N.D.*      16.2         11.4        1.5         8.3         4.2
                   01/11/89       6.5           N.D.*      10.1         1.9         10.4        30.2        6.7
                   01/24          9.8           0.7         N.D.**      7.4         7.8         1.3         0.5



                       N.D. - No Data

                       *On this date the MOR station was        equivalent to the 18% station.
                       **On this date the 18X station was equivalent to Tampa Bay.












                                                                   41










             Table 4   The annual mean cell concentration, the median cell concentration, and range, all as cells-ml-           for species that
                        occurred 4 13 sample dates during 1988-1989 in the Little Manat6e River. Data presented as: mean, median (range).

             Group              Species                        Tampa Bay      l8x            12X            6z              Ox             Ruskin Inlet
             flagellates        microflagellates               1664, 1906     1581, 1585     1925, 2185     2272, 3306      2713, 2485     2881. 2699
                                                               (137-3777)'    (1-7011)       (1075-4499)    (1071-5783)     (49-5326)      (372-5919)
             diatoms            unident. pennates              98, 14                                                       42, 36
                                                               (3-2003)                                                     (9-254)
                                Chaetocaros socialis           85, 70
                                                               (9-666)
                                Nitzschla closterium           89. 7          34. 3
                                                               (1-950)        (1-423)
                                Chaetoceros neogracile         41, 13
                                                               (1-754)
                                Leptocylindrus minimus         97. 17
                                                               (5-1978)
                                Ceratulina berganit            44, 11
                                                               (1-943)
                                Skeletonema costatum           3309. 686      429, 187       296. 257       365. 114        1565, 349      5147, 1310
                                                               (40-23740)     (52-3126)      (71-1924)      (0-2384)        (11-31331)     (14-80358)
                                Thalassionema nitzschoides     228, 33
                                                               (7-5419)
                                Chaetoceros subtilus           82, 28         165, 64
                                                               (4-674)        (5-1485)
                                Nitzschia longissima                                                                        4. 5           2, 4
                                                                                                                            (1-43)         (2-10)
                                Rhizosolenta setigera          10, 11
                                                               (1-89)
             Dinoflagellates    Prorocentrum minimum           3, 3                                                                        95, 33
                                                               (1-18)                                                                      (2-1213)
                                Prorocentrum micans            10, 8
                                                               (1-91)
                                Gymnodinium species                                                                         11, 7
                                                                                                                            (1-137)
             Chlorophytes       Schroederia   setigera                                                      8, 6            12, 13         9, 5
                                                                                                            (2-122)         (1-117)        (1-170)
                                Scenedesmus  quadracauda                                                    14, 3
                                                                                                            (3-58)
                                Rutreptle species                                                                                          38. 28
                                                                                                                                           (5-403)




















            Table 5    The frequency of occurrence for all specie    s at each station. Values are the number of sampling dates the species was
                       observed out of a total of 26 possible sample dates.


            TAXCD                    Species                                 Tampa Bay      l8x          12X       6Z      Ox          Ruskin Inlet


            Diatoms
                               102   unIdentifled pennates                   14               9          10         7      18          9
                               105   Chaetoceros socialis                    12             it           9          0         0        3
                               106   Nitzschia closterium                    13             18           11         5         2        12
                               107   Chaetoceros neogracile                  12               9          6          2         0        6
                               108   Nitzschia sigma                          3               1          1.         0         1        2
                               109   Leptocylindrus minimus                  16             10           8          3         0        8
                               110   Leptocylindrus danicus                   7               2          2          2         1        1
                               113   Ceratulina bergonii                     18               7          6          2         0        5
                               114   Eucampia cornuta                         3               1          0          0         0        0
                               115   Chaetoceros compressum                   8               4          0          0         0        0
                               116   RhIzosolenia fragillissima               2               1          1          0         0        0
                               117   Thalassiostra oestrupil                  5               3          1          0         0        1
                               118   Thalassiostra deciptens                 10               2          1          7         6        11
                               119   Amphora species                          6               3          1          0         0        3
                               120   Nitzschia longIssima                    12               8          11       12       13        .13
                               121   Rhizosolenia calcar-avis                 4               2          0          0         0        0
                               122   Rhizosolenia setigera                   13               9          5          1         0        2
                               123   Skeletonema costatum                    20             20           20       19       18          23
                               124   Rhizosolenta alata                       4               1          0          0         0        0
                               125,  Thalassiosira pseudonana                 5               8          10         7         7        11
                               126   Rhizosolenia delicatula                  5               1          0          0         0        1
                               127   Amphiprora species                       4               2          1          2      it          I
                               128   Rhizosolenia hebetata                    2               0          0          0         0        0
                               133   Amphiprora surfrelloides                 0               0          0          0         0        0
                               136   RhIzosolenia stolterforthii              2               1          0          0         0        0
                               137   Chaetoceros diversum                     2               1          0          0         0        0
                               138   Amphora cymbellfera                      1               0          0          0         0        1
                               139   Chaetoceros simplex                      1               1          0          0         0        1
                               140   Thalassiostra rotula                     I               1          0          0         0        .1
                               142   Asterionella glacialls                  10               3          0          0         1        0
                               141   Thalasslosira aJleni                     1               2          0          0         1        2
                               145   Dimerogramma fluvum                      0               1          0          0         0        0
                               147   Melosira nummoloides                     2               1          0          0         3        1


















            TAXCD                  species                              TmWa Bay      l8x       12X        6X        Ox        Ruskin Wet

           Diatoms
                             150   Nitzschia pulchella                                  0         0         0         0        0
                             151   Chaetoceros danicum                   2              1         0         0         0        0
                             152   Chaetoceros lorenzianus               4              5         0         0         0        0
                             153   Nitzschia pungens                    11              4         5         3         0        2
                             154   Chaetoceros curvisetus                3              1         0         0.        0        1
                             155   Chaetoceros subtilus                  7              8        16        16         4        9
                             156   Chaetoceros polygonum                 1              0         0         0         0        0
                             157   Dactylosolen mediterraneous           1              0         0         0         0        0
                             158   Chastoceros didymum                   2              0         0         0         0        0
                             160   Chaetoceros laciniosum                0              1         0         0         0        0
                             161   Amphiprora alata                      0              1         0         0         0        0
                             163   Melostra varians                      0              0         0         0         2        0
                             166   Nitzschia seriata                     1              0         0         1         0        0
                             180   Coscinodiscus centralis               0              1         0         0         0        0
                             185   Synedra species                       I              I         I         1         0        0
                             186   Coscinodiscus concinnus               0              1         0         0         0        0
                             190   Actinoptychus splendens               0              0         0         0         0        0
                             191   Thalassionema nitzscholdes           14              6         4         1         0        3
                             194   Coretheron hystrix                    2              0         0         0         0        0
                             196   Hemiaulls hauckii                     3              0         0         0         0        0
                             197   Tropidonsis lepidoptera               1              0         0         1         2        0
                             203   Bacteriastrum elongatum               1              0         0         0         0        0
                             204   Hemiaulis sinensis                    1              0         0         0                  0
                             208   Thalassiostra sp. (w/debris)          8              1         8         4         3        10
                             214   Guinardia flaccida                    2              0         1         0         0        0
                             218   Coscinodiscus radiatus                0              0         1         0         0        0
                             222   Cyclotella meneghiniana               0              0         0         0         1        1
                             224   Nitzschia rigida                      0              0         0         0         1        .0
                             230   Biddulphia pulchella                  1              0         0         0         0        0
                             231   Thalassiosira hyalina                .1              0         0         0         0        0
                             236   Thalassiothrix frauenfeldianum        3              0         0         0         0        0
                             238   Bacillaria paxillifera                1              0         0         1                  0
                             241   Skeletonema tropicum                  0              0         0         0         0        0
                             242   Thalassiosira grsvida                 0              1         1         0         1        0
                             244   Coscinosira polychorda                3              0         0         0         0        0
                             248   Rhizosolenia inermis                  0              0         0         0         1        0
                             249   Chaetoceros gracile                   1              0         0         0         0        0




















             TAXCD                   Species                               Tampa Ray      lex         12X       6X       CIL      Ruskin Inlet
             Diatoms           250   Rucampia zoodiacus                      1              0         0          0         0        0
                               251   Chaetoceros breve                       I              1         0          0         0        0
                               253   Chaetoceros deciplens                   0              0         1          0         0        0
                               254   Melos1ra species                        4              0         0          2         3        0
                               257   Attheya species                         0              0         0          0*        1        0
                               263   Cyclotella species                      0              3         4          5        12        6
                               267   Hastogloea species                      0              1         O@         0         0        0
                               273   Hantzschia species                      0              0         0          0         0        1
                               278   Havicula species                        3              1         2          0         0        0
                               279   Nitzschia species                       1              0         2          0         1        0
                               280   Coscinodiscus species                   3              0         0          0         0        1
                               281   Pleurosigma species                     5              2         0          2         4        0
                               282   Chaetoceros species                     5              2         2          0         0        0
                               284   Llcmophora species                      0              0         0          0         0        0
                               289   Gyrosigma species                       1              0         0          1         1        1
                               295   Chaetoceros p.eruvianus                 1              0         0          0         0        0
                               296   Thalassiosira aestivalls                0              0         0          0         0        1
                               298   Nitzschia lineata                       0              0         0          0         1        0
                               299   Cyclotella species (small)              0              1         2          7         7        1
                               300   Thalassiosira species                   1              0         0          0         0        0
                               301   Cyclotella species (large)              0              0         1          1         6        0
             Microflagellates  101   microflagallates                      24             22                    19       25       24
             Dinoflagellates
                               103   burst dinoflagellate                    5              0         3          7         1        3
                               Itl   Prorocentrum minimum                  13               6         6          4         3      15
                               112   Prorocentrum micans                   15               4         4          0         0        3
                               134   Peridinium nipponicum                   0              1         0          0         0        0
                               144   Peridinium turbo                        1              0         0          0         0        0
                               146   Gonyaulax polyedra                      0              1         .0         0         0        0
                               148   Peridinium tuba                         5              2         1          0         0        0
                               162   Peridinium trochoideum                  0              0         0          0         1        2
                               164   Ceratium hircus                       11               3         2          0         0        1
                               165   Oxytoxum scolopax                       1              0         0          0         0        0
                               167   Proocentrum gracile                     2              1         1          0         0        0
                               187   Gonyaulax grindlyl                      0              0         1          0         0        0
                               188   Peridinium aciculiferum                 1              8         10         8         1      11



















             TAXCD                  Species                              Tampa Bay     18X       M           6x       a%      Ruskin Inlet

             Dinoflagellates
                              189   Gonyaulax diacantha                    0             0         0          0        0        0
                              195   Peridinium concinum                    3             0         1          2        0        1
                              198   Gonyaulax spinifera                    0             3         4          0        0        2
                              201   Peridinium depressum                   1             0         0          0        0        0
                              202   Perldinium claudicans                  1             1         0          0        0        0
                              205   Peridinium divergens                   2             0         0          0        0        0
                              206   Peridinium oblongum                    I             1         0          0        0        0
                              207   Dinophysis caudata                     2             1         1          a        0        2
                              209   Amphidtnlum globosum                   0             0         1          0        0        0
                              211   Gonyaulax polygrama                    3             4         3          7        0        3
                              212   Gymnodinium estuariale                 0             0         0          0        0        0
                              215   Ganyaulax digitalis                    2             0         1          1        0        2
                              .216  Peridinium brochii                     0             0         1          0        0        0
                              219   Gonyaulax monilata                     3             1         4          0        0        1
                              229   Oxytoxum gigas                         1             0         0          0        0        0
                              262   Amphidinium species                    1             0         0          1        0        0
                              276   Gymnodinium species                    5             5         7          9       13        9
                              283   Oxytoxum species                       1             0         0          0        0        0
                              287   Scrippstella species                   5             4         4          2        4        9
                              291   Coolia species                         2             1         0          0        0        0
                              29T   Perldinium species                     7             4         3          5        0        6
                              303   Peridinium crassipas                   0             0         1          0        0        0
             Blue-greens
                              104   Blue-green filaments                   I             I         a          2        6        4
                              171   Herismopedia punctata                  1             0         0          2        6        5
                              210   Anabasnopsis trichomes                 0             0         0          0        0        0
                              217   Schizothrix species                    8             5         6          4        0        4
                              221   Spirulina species (trichomes)          0             0         0          0        0        1
                              227   Oscillatoria species (trichomes)       0             0         0          0        0        2
                              228   Nostoc species (trichomes)             3             1         1          3        2        4
                              258   Hicrocystis species                    0             0         0          0        1        0
                              270   Ohrmidium species (trichomes)          0             0         0          0        1        0
             Chlorophytes
                              100   Crucigenia species                     1             0         0          1        7        5
                              130   Akistrodesmus species                  0             1         2          0        0        1
                              131   Euglena species                        0             2         2          4        5        6
                              135   Scenedesmus quadracauda                1             1         2          9       14        5
                              149   Asterococcus superbus                  0            @o         0          0        1        0

















              TAXCD                   Species                              Tampa Bay      18X        12X         6X      COL       Buskin Inlet

              Chlorophytes
                                168   Scanedesmus acuminatus                 0                                    3        6         2
                                169   Cruc.igenia fenestrata                 0             0           1          0        0         0
                                170   Tetrastrum staurogeniaeforme           0             0           1          0        0         0
                                172   Akistrodesmus gracilis                 0                         0          1        3         1
                                173   Akistrodesmus falcatus                 1             0           0          5      11          6
                                174   Clostridium species                    0             0           0          0        1         0
                                175   Scenedesmus bijinga                    I             1           0          4      11          4
                                176   Schroederia setigera                   2             0           6         14      14         13
                                177   Phacus pleuronectus                    0             0           1          0        1         0
                                178   Selenastrum gracile                    0             0           0          1        4         2
                                179   Tetraedron species                     0             0           0          0        1         1
                                181   Scenedesmus actus                      0             1           1          1        2         0
                                182   Tetrastrum species                     0             0           0          1        3         1
      -4                        183L  Akistrodesmus convolulus               0             0           0          0        0         1
                                184   Tetrastrum haterocontum                0             0           0          0        2         0
                                192   Schroederia anchora                    0             0           0          0        1         0
                                193   Scenedesmus arcuatus                   0             0           0          0        2         0
                                199   Crucigenia quadratus                   0             0           0          1        0         1
                                213   Staurastrum paradoxym                  1             0           0          0        0         1
                                220   Scenedesmus abundans                   0             0           0          0        3         0
                                223   Agmenellum quadrupliatum               0             0           0          0        0         1
                                226   Franceia tuberculata                   0             0           0,         0        1         0
                                233   Akistrodesmus acuminatus               0             0           0          0        2         0
                                234   Actinastrum hantzschi '1               0             0           0          0        3         0
                                235   Micractinium pusillum                  0             0           0          0        3         0
                                237   Pediastrum borfanum                    0             0           0          0        1         0
                                239   colonial chlorophyte                   0             0           0          1        1         0
                                240   Scenedesmus denticulus                 0             0           0.         0        1         0
                                243   Akistrodesmus fractus                  0             0           0          0        1         1
                                246   Treubania crassispina                  0             0           0          0        0         1
                                247   Polyedriopsis spinulosa                0             0           0          0        1         0
                                252   Pediastrum simplex                     0             0           0          0        0         1
                                255   Pediastrum species                     0             0           0          0        0         1
                                256   Gloenkia species                       0             0           1          0        0         0
                                259   Oocystis species                       0             0           0          0        0         1
                                261   Phacus species                         0             1           0          0        4         1
                                264   Dictyosphaerium species                0             0           0          0        2         0



















            TAXCD                  species                              Tampa Bay     lax        12X        6X       Ox      Ruskin InUt

            Chlorophytes
                             265   Westella species                      0              0         0          0        2        0
                             268   Scenedesmus species                   0              1         1          0        3        1
                             269   Gloeocapsa species                    0              0         0          0        1        0
                             274   Selenastrum species                   0              0         0          0        1        0
                             275   Franceia species                      0              0         0          0        1        1
                             277   Hicratinium species                   0              0         0          0        1        0
                             285   Eutreptia species                     2              5         9          5       11       15
                             286   unknown Chlorophyte                   0              0         0          0        2        0
                             288   Actinastrum species                   0              0         0          1        0        0
                             290   Desmidium species                     0              0         0          0        0        0
                             193   Kirchneriella species                 0              0         0          0        1        0
                             302   unidentified Chlorophyte              0              a         0          0        1        0
                             304   Crucigenia tetrapedia                 0              0         0          0        1        0
            Silicoflagellates
      00                     132   Dictyocha fibula                      2              0         1          0        0        0
                             141,  Ebria tripartita                      3              2         2          0        0        0
            Chrysophytes
                             266   Dinobryon species                     0              0         0          0        2        1
                             297   unknown Chrysophyte                   0              0         0          0        0        1
            Prymesiophyte
                             271   Pyramimonas species                   I              1         0          1        1        3












                  Table 6          Simllarity index of comparisons between community composition at
                                   Tampa Bay with all LMR stations.

                                                             Station
                  DATI         HOR        18%           12%             6X             R. Inlet         Ox


                  1988
                  1/26         0.51       0.60                                         0.49             0.22
                  2/10         0.60       0.64                                         0.44             0.16
                  2/24         0.57       0.47                                         0.37             0.22
                  3/9                     0.45          0.48                           0.33             0.19
                  3/22         0.57       0.62          0.70                           0.35             0.22
                  4/6                     0.61          0.44                           0.49             0.21
                  4/20         N.D.       N.D.          N.D.            N.D.           N.D.             N.D.
                  5/4                     0.43          0.50            0.24           0.62             0.19
                  5/18                    0.60          0.20            0.14           0.33             0.18
                  6/1                     0.40          0.25            0.14           0.50             0.18
                  6/15                    0.25          0.22            0.13           0.22             0.29
                  6/29                    0.50          0.33            0.24           0.50             0.13
                  7/14                    0.36          0.34            0.26.          .0.41            0.19
                  7/28                    0.57          0.38            0.23           0.37             0.19
                  8/10                    N.D.          0.55            0.34           0.20             0.09
                  8/30                    0.62          0.53            b.21           0.18             0.26
                  9/8                     0.44          N.D.            0.40           0.34             0.36
                  9/22                    0.32          0.51            0.59           0.32             0.20
                  10/11        0.35       N.D.          0.52            0.37           0.27             0.16
                  10/25                   0.36          0.33            0.08           0.31             0.24
                  11/7                    0.50          0.36            0.23           0.22             0.12
                  11/21                   0.24          0.29            0.16           0.23             0.24
                  12/8                    .0.48         0.27            0.14           0.47             0.27
                  12/20                   0.42          0.11            0.25           0.36             0.17

                  1989
                  1/11                    0.23          0.31            0.25           0.39             0.24
                  1/24         0.24       N.D.          0.53            0.31           0.32             0.21
                  Annual'                 0.445         0.388           0.248          0.360            0.205
                  Mean


                               N.D.   No Data



















                                                                49











                   Table 7           ValVas for the Shannon-Weaver diversity index                 for the combined
                                     replicate counts for each LMR station. Identification to Genus was
                                     the lowest taxonomic criterium used for the calculation; therefore
                                     flunidentified" groups and microflagellates were not            .included.



                   DATZ    TAMPA MY        MDR         1 V.        121        9X        &L       R Inlet aL

                   1988
                   1/26      -0.450       -2.279       -0-839                -1.673              -2.226      -2.863
                   2/10      -0.684       -1.211       -1-312                                    -0.895      -2.137
                   2/24      -0.577       -1.020       -1.268                -2.079              -1.309      -0.938
                   3/9       -2.385                    -2.445      -2.986                        -1.936      -0.973
                   3/22      -3.029       -2.559       -4.068      -3.174                        -2.415      -2.448
                   4/6       -1.452                    -1.794      -2.016                        -1.641      -1.899

                   .5/4      -1.214                    -0.670      -2.285             -1.701     -1.195      -1.534
                   5/18      -0.360                    -1.454      -1.279             -2.104     -0.768      -0.264
                   6/1       -1.023                    -1.830      -0.903             -1.259     -0.141      -1.421
                   6/15      -0.000                    -1.049      -0.484             -1.413     -0.082      -2.157
                   6/29      -0.492                    -1.272        1.556            -1-916     -0.120      -1.803
                   7/14      -2.927                    -0.457      -1.747,            -1.764     -0.619      -2.232
                   7/28      -0.858                    -1.877      -2.399             -2.045     -1.525      -2.090
                   8/10      -0.909                     N.S.       -1.609             -2.607     -4.599      -2.566
                   8/30      -1.879                    -3.010      -2.313             -2.193     -2.535      -1.777
                   9/8       -1.844                    -1.499       N.D.              -2.142     -2.102      -1.621
                   9/22      -1.249                                -1.786             -0.726     -1.653      -2.812
                   10/11     -1.526       -0.689        N.D.       -0.549             -0.878     -0.044      -0.610
                   10/25     -2.052                    -2.495      -1.520             -1.491     -1.209      -1.291
                   11/7      -0.845                    -1.586      -1.226             -1.924     -0.390      -2.596
                   11/21     -1.288                    -1.128      -1.403             -1.662     -1.725      -1.899
                   12/8      -2.032                    -2.055      -1.374             -1.338     -1.941      -1.679
                   12/20.    -0.341                    -1.944      -1.887             -2.013     -2.177      -2.089


                   1989
                   1/11      -0.963                    -2.829      -1.478             -2.127     -2.177      -2.089
                   1/24      -2.440       -1.992        N.D.       -2.100             -2.038     -1.348      -2.643

                   Annual    -1.231                    -1.757      -1.718             -1.755     -1.409      -1.833
                   Mean


                                 N.D. - No Data
                                  N.S. - Not Sampled












                                                                         50













                  Table a         Ratios of dark carbon -14 uptake with and without the addition of
                                  ammonium. Ratios are expressed as: CPM with ammonium / CPM without
                                  ammonium (D+/D-) and as the average uptake rate in the dark bottles
                                  with ammonium minus the a   erage uptake rate in dark bottles without
                                         ium (V D+-V D- ; mgCm- hr-1).


                                  T. Bay                 NOR                 9X                   0%
                  DATE       D+/D-    V +-V        D+/D-   V    -V      D+/D-   VD+-VD-      D+/D-   VD+-VD-
                                         D  D-              D+ D -


                  1988
                  1/26       1.18        +0.32     1.09     +0.02       0.92        -0-       -0-     -0-
                                                         l8X
                  1988
                  2/10       1.58        1.17      1.98     +1.25       0.73 IZY. 0.90        0.48     N.S.
                  1988
                  2/24       1.21        0.14      0.76       -0-       1.15      0.11        1.57     0.54
                  3/9       .1.39        0.46      1.11       0.13      1.28      0.78        1.34     0.34
                  3/22       1.29        0.46      1.68       0.92      1.49      0.45        1.59     0.52
                  4/6        1.19        0.47      1.24       0.93      1.81      1.68        1.59     1.42
                  4/20       1.14        0.37      1.32       0.42      1.30      0.52        1.39     0.86
                  5/4        1.73        0.85      1.62       0.87      1.17      0.30        1.38     0.74
                  5/18       0.85        -0-       1.34       0.69      2.34      1.91        1.72     1.58
                  6/1        1.47        1.32      1.32       0.70      1.23      0 39        0.99     -0-
                  6/15       1.09        0.37      1.61       1.37      1.14      0,49        0.91     -0-
                  6/29       1.36        0.86      1.66       1.46      0.98.     -0-         0.0      -0-
                  7/14       0.73        0-        1.63       1.20      1.91      3.81        1.16     0.30
                  7/28       1.35        1.03      2.21       2.89      0.82      -0-         1.48     0.39
                  8/10       1.14        0.68      0.69       -0-       1.38      1.44        1.06     0.11
                  8/30       1.12        1.16      0.93       -0-       1 04      0.22        0.90     -0-
                  9/18       1.38        0.28      0.92       -0-       N:S.      N.S.-       1.19     0.09
                  9/22       0.82        -0-       N.S.       N.S.      0.82      -0-         1.13     0.44
                  10/11      1.69        2.35      N.S.       N.S.      0.86      -0-         1.12     0.26
                  10/25      1.27        0.92      1.06       0.17      1.08      0.24        1.49     1.36
                  11/7       1.56        0.13      1.43       0.38      1.27      0.30        1.32     0.34
                  11/21      1.13        0.14      1.19       0.19      1.13      0.18        1.86     1.10
                  12/8       1.41        0.35      1.11       0.10      1.38      0.30        1.63     0.83
                  12/20      1.05        0.06      1.37       0.32      0.95      -0-         1.26     9.24


                  1989
                  1/11       1.54        0.59      1.28       0.28      1.62      0.76        1.24     0.44
                  1/24       0.63        -0-       N.S.       N.S.      0.78      -0-         1.02     0.02

                             -0-       L-D =  0 or negative

                             N.S       Not Sampled






                                                                51









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