Mangrove forests ecology and response to natural and man induced stressors

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

Coral Reef, Seagrass Beds and Working paper
Mangroves: Their interaction in UNESCO/W.I.L.-F.D.U./
the coastal zones of the Caribbean. IOCARIBE
Workshop.
West Indies Laboratory, Fairleigh
Dickinson University
St. Croix, U.S.V.I.
24-30 May 1982

LIN
MANGROVE FORESTS: ECOLOGYAND RESPONSE
TO NATURAL AND MAN TNDUCED STRESSORS

COASTAL ZONE

INFORMATION CENTER

SD-
397
.M25 Document prepared by Gilberto Cintr6n, Director of the Marine Resources
C56 Division, Department of Na tural Resources of the Commonwealth of
1982 Puerto Rico, and Yara Schaeffer-Novelli, Instituto Oceanografico Univer-
3idade de Sao Paulo, Brasil. Document prepared for use by workshop
participants

CONTENTS Pa ge
1. INTRODUCTION I

2. DEFINITION I

3. DISTRIBUTION 2

4. SPECIES 4

5. ADAPTATIONS AND ZONATION 4

6. ZONATION AND SUCCESSION 7

7. PHYSIOGRAPHIC TYPES 9

7.1 Riverine forests 10
7.2 Fringe forests 10
7.3 Basin forests 11
7.4 Dwarf, forests 12

8. PRODUCTIVITY 12

9. DECOMPOSITION AND UTILIZATION OF LITTERFALL 13

10. FISHERIES 15

11. CLIMATIC CONSTRAINTS ON DEVELOPMENT 16

12. VULNERABILITY TO STRESSORS, 18

12.1 Natural stressors 19

12. 1. 1 Tropical cyclones 19
12.1.2 Tidal waves 23
12.1.3 Eustatic sea level rise and
coastal erosion 23
12.1.4 Hypersalinity 24

12.2 Man induced stressors 27

12.2.1 Channelization 27
12.2.2 Impoundment 27
12.2.3 Sedimentation 28
12.2.4 Thermal pollution 29
12.2.5 Oil 30
12.2.6 Mining 33

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Contents (Cont.)
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13. RECOVERY 33
1 14. CONCLUSION: CONSERVATION NEEDS 37
1 15. BIBLIOGRAPHY 39
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1. INTRODUCTION

Until very recently, mangrove swamps were seen as mosquito-

infested wastelands, unfit for most uses, but convenient sites for open

dumps and sewage discharges. Mangrove management meant "reclama-

tion, " either for agricultural purposes or housing developments. Mangrove

forests are, however, among the most productive ecosystems on the planet.

Their daily rate of organic matter fixation (" 20 g.O.M./m2-day) is about

70 times the maximum value reported for tropical oceanic waters and 6

times the mean for the rates reported for marine flagellate blooms in neritic

waters in the Caribbean (Ryther, 1969; Burkholder et al., 1967). Because

of this high rate of production of organic matter, they are able to sustain

important and valuable populations of fish, shellfish and wildlife and are

prime breeding and nursery grounds for many species.

The main reason that mangroves have been consistently undervalued

and poorly managed in our region is the lack of available information about

the resource, its role and vulnerability. In this paper, we summarize

some basic information about the ecology of these forests in our geographic

region.

2. DEFINITION

The word mangrove is employed to describe a group of plants adapted

to colonize waterlogged anaerobic and saline soils. They grow as trees

or shrubs along most tropical estuaries and sheltered shores. The term is

also used to describe the complex a ssamblage of animals and other plants

a s socia ted with this- forest type.

3.' DISTRIBUTION

Mangroves are limited on a global scale by temperature and their

lack of tolerance to frost. They extend latitudinally beyond the tropics,

reaching in places to 29-301n both hemispheres. At these latitudes, the

mean monthly temperature for the coldest month is between 15 and 1611 C,

the mean annual temperature is 20-221 C and the annual temperature

amplitudes range from 8-131 C. Frosts occur periodically at these areas

and at the latitudinal limits the mangrove forests are poorly developed

and grade into salt marshes dominated by herbaceous vegetation. Black

mangroves (Avicennia sp.) are most frost tolerant and have the widest

latitudinal range. Within the warmer portion of their range temperature

is not limiting but the following other factors remain to be determinants

or modifiers of their degree of development and areal coverage.

Suitable Physiograph : Mangroves develop in low lying areas

subjected to saline intrusions. They develop best where topographic

gradients are very small and saline intrusions penetrate far inland, for

example on broad coastal plains.

Presence of salt water. Mangroves are not obligate halophytes but

salt water removes the competition from plants that lack adaptations to

deal with salt.

Large tidal amplitude: Tidal intrusions force salt wedges into the

low lying areas. Where the tidal amplitude is large and the topographic

gradient small, the mangrove belt may reach several kilometers in thick-

ness.

Precipitation in exce-ss of evapotranspiration (P > PET); Mangroves

develop best in moist regions where there are fresh water surpluses. This

results in abundant land drainage and extensive development of forests in

the areas subjected to sa line - intru s ion s

River discharge Rivers are important geomorphic agents that shape

the earth's surface and create deltaic features over which mangroves

develop. In some regions their discharge may allow mangroves to develop

in very *dry regions where evapotranspiration greatly exceeds precipitation.

In these areas, mangroves develop as riverine forests backed by extensive

salt flats. Mangroves may develop in areas where there are no permanent

A river discharges (coastal fringes), but their development in these areas

is. limited,... The absence of river discharges can -be- mitigated by.the

availability of runoff or fresh water upwellings.

Shelte Mangrove seedlings and mature trees are vulnerable to

uprooting by waves and current scour. They therefore develop best in low

energy environments. They reach the sea only on protected segments of

the coast, on the lee of offshore reefs, shoals or other protective struc-

tures. They line sheltered estuaries and coastal lagoons.

Availability of allocthonous sediments: Sediments from outside

area sare essential for land building and encroachment. Terrestrially

derived sediments bring nutrients that are incorporated by the plants.

Although mangroves may develop in areas where there are very low alloc-

thonous sediment inputs, @the best developed forests are those of riverine

environments that are subjected to periodic deposition of silts.

4. SPECIES

In contrast to the Indo-Pacific region, where mangroves are thought

to have originated, and where there are some 44 species, in the Caribbean

region only seven species are present. These are the red mangroves

Rhizoph mangle R. harrisonni and R. racemosa; the black mangroves

Avicennia germinans and A. schaueriana; the white mangrove Laguncularia

racemosa and the buttonwood Conocarpus erecta. Of the red and black

mangroves, only R. mangle and A. germinans are widely distributed in

the Caribbean. The iabt two species, racemosa (white mangrove) and

C. erecta (buttonWood) are found throughout the region. The buttonwood

is considered a peripheral species and quite often is found in coastal

nonmangrove associations.

5. ADAPTATIONS AND ZONATION

Several environmental factors determine the position of individual

species in a forest. For instance, in a fringe one may observe variations

in terms of tidal exposure, salinity gradients and different soil types and

textures with distance inland. Each species has adaptations that allow

it to cope best with the site's factors with the least metabolic cost.

This means that more energy can be alloted for growth and reproduction

allowing that species to become highly competitive and ultimately

dominant. This may lead to an observable zonation of species in a man-

grove stand.

Red mangroves are usually found at the outer edges of a fringe or

bordering tidal creeks and channels. This species has a large propagule

(seed) that can reach some 30 cm long and weigh 30@-40 g. Upon settle-

ment the sapling quickly develops supporting roots that protect the young

plant from washout. This prop root system is surprisingly responsive to

the environment (Gill and Tomlinson 1977). Very complex prop ro ot mazes

develop in some fringe forests, possibly as a response to wind and wave

stresses. The trees growing on more stable substrates often develop very

erect boles and have proportionately fewer prop roots. These character-

istics: the ability to become implanted ixi. deeper water (up to.30 cm)

and to windstand dislodgement by water movement, contribute to allow

this species to become dominant in the outer fringes. Red mangrove has

a low tolerance to high salinities. It actually develops best at low

salinities (10-200/oo) but will form forests, even where salinities reach

50-55'Yoo. These salinity levels are very close to the limits of its

tolerance, and growth and development are poor under hypersaline

conditions.

Black and white mangroves tolerate higher salinity levels and thrive

in higher salinity substrates with a greater metabolic efficiency (Carter

et al. 1973). These species are typical of.the inner swamp where tidal

flooding is less frequent and evapotranspiration contributes to accumulate

salts. Black mangroves, are the most salinity tolerant. Scrub forests are

found in soils with interstitial salinities of 90961o. Well developed forests

are found where interstitial salinities are 60-65961o. Although white man-

groves are also fairly tolerant of high salinities, they seem to do best

where these are not so high.

In general, in tropical areas, where there are ample fresh water

flows and interstitial salinities are low, the white mangrove dominates.

In areas where there are pronounced drought periods and salinities are

high, black mangroves may be dominant.

The relative stagnation of water in basin forests requires special

adaptations to allow ventilation of the root system. Black and white

mangroves, have adaptations. to overcome this.problem. They.ventilate

their root system by producing networks. of chimney-like organs

(pneumatophores). These arise from the root and project from the soil

and the stagnant water surface. The surface of the pneumatophore has

minute pores through which gas exchange takes place. In this way

oxygen diffuses down to the root and carbon dioxide is vented out.

These pneumatophores reach 10-30 cm in length depending on the site's

flooding levels. They are never totally flooded for extended time periods

since this would result in the eventual death of the tree.

These species also have small seeds. This is advantageous since

the floating propagules can be disseminated by the weak water flows

typical of these areas. The movement of small seeds is not as easily

hampered by the profuse growth of pneumathophores.

Because of the smaller size of the propagule, the implantation depth

is more restricted (10-15 cm). In general black mangroves appear to tole-

rate deeper and longer flooding than white mangrove. In this respect,

black mangroves'may be dominant in low salinity environments subjected

to large seasonal changes in water level.

The buttonwood is a peripheral species. It has a low tolerance to

salinity but can stand flooding by very brackish waters , usually where

the salinity is less than 5516o. It does well in sandy or rocky substrates

and may be found in areas that are not flooded. A few pure stands of

Conocarpu s occur in Puerto Rico in permanently flooded basins where

salinity. is Jess. than 55,c'o

6. ZONATION AND SUCCESSION

It has been suggested that the zonation observed in a mangrove

swamp is the result of a succession of species (Davis 1940, Macnae

1968). According to Davis , the red mangrove is the pioneer species

that prepares the way for the others. As this species progressively

grows toward the sea , accretion takes place, and in the inner parts of

the prograding fringe it is replaced by the black mangrove. Eventually,

black mangrove is also replaced by the white mangrove, which gives way

to buttonwood or fresh water swamps. This scheme suggests that man-

groves are the 'causal' agent of coastal progradation. It now appears

that mangroves are not the cause of the rapid accretion but that they are

responding to coastal accretionary patterns. In this sense-they contri-

bute to stabilize rapidly accreting banks and shoals but the extent to

which they promote accretion is uncertain '(Bird 1976).

Davis' scheme is applicable only in some instances where sedi-

moint inputs are high and there is active coastal progradation and

freshwater runoff, since in some areas the landward succession could

be arrested by dry conditions. In areas where there are no large fresh-

water and sediment inputs , as in most of the dry portions of the Caribbean

islands, mangroves develop over autocthonous peats. Progradation under

these circumstances is very slow and may be surpassed by the known

rise in sea level which is estimated to be some 3 mm/yr (Emery 1980 as

cited byTtkins and Epstein 1982). . In most instances , mangroves have

retreated landwards due to the submergence of land masses during the

Holocene transgression. Zonation patterns in these sediment starved

areas are a response of the various species to environmental factors and

do not necessarily 'recapitulate' successional patterns.

An analysis of old aerial photography (1936) to ascertain the patterns

of establishment after a hurricane in southwest Puerto Rico (Cintr6n et al.

1980a) shows that there has been little or no peripheral accretion.

Suitable areas were immediately recolonized and the present zonation
pattern'did not result from a successional of species.

7. PHYSIOGRAPHIC TYPES

Mangrove forests vary greatly in their structural development. This

structural variability is the response of the trees: to the sum total of

particular environmental factors, each of which can vary both in intensity

and in frequency of recurrence. Individual forcing functions , or environ-

mental factors , that control mangrove structure include tidal fluctuations

(with daily, monthly and annual cycles), runoff and groundwater perio-

dicity (usually over annual or longer cycles) , nutrient inputs (usually

tied to runoff hydroperiods) , droughts (sometimes over periods of several

years) , soil salinity, etc. It is not usually possible to quantify all these

factors to describe the so-called "energy signature" of each stand.

Snedaker and Pool (1973) and Lugo and Snedaker (1974) developed a clas-

sification scheme that grouped mangrove forest types in units in which
t.he.-ma-jor''for-ding fun-ctions -operate at similar levels within each unit.

Because of this , forest types within each unit share similar structural

characteristics. Originally these authors recognized five types :

(1) fringe forests , (2) riverine forests , (3) overwash fore s ts , (4) ba s in

forests (including hammocks) and (5) dwarf forests (Lugo and Snedaker

1974). More recently, after a review of all the available quantitative

structural data available, we simplified the previous scheme by i ncor-

porating overwash forests as a type of fringe and considering dwarf

forests a type of basin. The description of these forest types , taken

from Cintr6n et al. (1980) and Cintr6n and Novelli (198 1) , follows:

7. 1. Riverine forests

Riverine forests develop along the edges of river estuaries , often

as far inland the toe of the.saline intrusion. In this environment water

flows and nutrient inputs are high. Flood waters bring in silts and

mineral nutrients and these are rapidly incorporated into plant tissue.

On the periphery of the forest, an area of high kinetic energy due to

tidal motion and river discharge, the dominant species is Rhizophora.

sp. , which develops a complex maze of adventitious roots. This root

maze allows the establishment of well developed trees in spite of the

strong water flows. Inland from the fringe one finds stands of

Laguncularia sp. and Avicennia sp. Usually, riverine forests are most

luxuriant in the lower and middle part of the estuary. Generally, inter-

stitial salinities in these forests are lower than in the other types.

They are lowest at times of flood when the salt wedge is driven seaward.

During times of low flow, salt intrudes into the innermost parts of the

estuary, raising the salinity temporarily. Usually interstitial salinities

are in the range of 10-200/oo or less.

7.2. Frincie forests

Fringing mangroves develop along protected shores , over shoals or

spits , often forming overwash islands. Fringes usually have pronounced

gradients in topography, turbulence and tidal amplitude. Damping of the

variation in tidal amplitude and turbulence inside the stand may result

in high interstitial salinities in the inner parts of the fringe. There, the

soil elevations are high and the terrain is less often flooded. In these

inner portions Avicennia sp. may become dominant. On the outer edge

where the levels of kinetic energy are high Rhizopho sp. dominates .

Interstitial salinities in the outer fringe are just above ambient sea water

(39 � 1.39o'o) , but increase to higher levels (59 47w) in the Avicennia sp.

zone (Cintr6n et al. 1980a).

7.3. Basin forests

Basin mangroves are characterized by sluggish laminar water flows

over wide areas of very small topographic gradients. The water turnover

rate is slow. Basins receive and store water seasonally. Because of the

uniform sheet flows strong salinity gradients do not develop within the

basin. Basin forests may be dominated by either Laguncularia sp. or

Avicennia sp. , although mixed stands may be found. Tidal creeks and

drainage channels within the basin are often lined with Rhizophora sp.

Avicennia sp. dominates in basin forests where high salinities prevail

(> 50%) , whereas Laguncularia sp. dominates in low salinity basins .

Mixed forests are found at intermediate salinities (30-400/0').

The structural characteristics of basin forests depend on the hydro-

period. Where flows are weak but constant, forests develop well. In

stagnant basins there may be oxygen depletion, slow nutrient recycling

and reduced growth.

7.4. Dwarf forests

Dwarf forests occur where growth is limited by edaphic factors.

Stands of dwarf Rhizophora mangle develop in some areas of the Caribbean

over peat substrates in basins that do not receive substantial amounts of

terres-trial runoff. Mature red mangrove trees in these basins are usually

less than 2 m tall and often are about 1-1 1/2 m in the inner parts of the

stand. Dwarf stands of R. mangle develop over marl in Florida, USA.

It appears that in both instances (growth over peat and marl) the plants

are being subjected to nutrient deficient (oligrotrophic) conditions.

Dwarf stands of Rhizophora are known from Puerto Rico, St. Thomas

(U.S.V.I.), and Paso de Cattlan in the Dominican Republic.

Dwarfed black mangroves are often found on the landward side of

fringes and basins in seasonally dry areas , immediately adjacent to salt

flats or hypersaline lagoons. The dwarfing factor here is extremely high

levels of salt in the soil.

8. PRODUCTIVITY

Table 1 is a summary of productivity data from Lugo and Snedaker's
(1974) review. The data have been converted from gC/m2-day to grams

of organic matter/m2 -day and presented by forest type. These numbers

were obtained from gas exchange studies and represent total community

metabolism. Riverine forests show very high rates of gross production
(24g 0. M./m2 -day), followed by basins (18g 0. M./m2 -day), and

fringes (1 3.2g 0. M. /m2 -day) . Net , production is the amount of organic

matter left after metabolic losses are accounted for. This is the amount

of organic matter available for growth, foliage and seed production. These

rates are also high. Between 20 and 40% of net production is partitioned

for the production of leaves , flowers , fruits and stipules, which constantly

fall to the,forest floor.

Litterfall rates (dry weight) are highest in ri verine forests
(2.94 - 3.96 g/m2 -day), slightly less in fringe forests (2.0.g/m2 day)

and intermediate in value in basins (1. 9 - 2. 3 g/m2 -day) (Pool et al.

1975). Well developed riverine forests in Puerto Rico have litterfall
rates averaging 4.12 g/m2 -day (Negr6n 1980). A monospecific black
mangrove basin in Puerto Rico averaged 2.29 � 0.30 g/m2 -day (Negr6n

and Cintr6n 1981). Litterfall rates in Avicennia sp. , Rhizophora sp. ,

and Laguncularia sp. stands in Guadeloupe were 3.56, 4.33 and 2.74
g/m2 -day, respectively (Febvay and Kermarrec 1978).

9. DECOMPOSITION AND UTILIZATION OF LITTERFALL

It is now recognized that one of the primary reasons mangrove

areas are so important is because of their high rates of productivity

of organic matter as litter. This material falls to the forest floor where

it starts to decompose. During this time soluble organics are leached

out and the leaf surfaces are colonized by fungi and bacteria. In time

a complex meiofaunal assemblage develops, grazing on the decomposers.

The decomposing material, originally high in carbohydrates and low in

proteins , becomes enriched with microbial protein. The C:N ratio of the

plant material decreases during decomposition. In R. mangle the C:N

ratio decreases from 90,6 to 40.7 during the first 70 days of the decom-

position process (Cundell et al. 1979). These low C:N ratios indicate

the greater nutritional value of the decomposing material. As a result

of decomposition, and the intense activity-of grazing organisms the plant

material is gradually reduced to very small particles. These detrital

particles enriched with microbial tissue, are consumed by detritivores.

These derive their nutrition primarily from the microbial and meiofaunal
assamblage associated with the detrital particle. Once consumed, the

particle is stripped of its microbial and meiofaunal cover and egested.

The undigested stripped particles may become recolonized by microbes,

repeating the cycle anew until all the digestible components are utilized.

As stated earlier, the initial autolysis of the plant material releases

large amounts of dissolved organic matter to the water. This DOM is an

important component of the outflux from mangrove areas, especially from

basins where tidal and freshwater flows are too weak to export particulate

matter. Bacteria are known to be important in the uptake and utilization

of DOM.

Prackash (1971) has shown thatblooms of the bioluminescent

dinoglagellate Pyrodinium bahamense are stimulated by humic substances

from mangrove areas . These humic substances also enhance the produc-

tivity of other neritic diatoms such as Skeletonema costatum and

Thallassiosira nordenskioldii (Prakash et al., 1973). Thus, there is

evidence that the waters leaching from mangrove areas appear to be rich

in biologically active substances which can stimulate or regulate phyto-

plankton production in adjacent waters.

10. FISHERIES

Given the continuous availability of large amounts of nutritious

organic matter in mangrove lined areas , it is not surprising that large

numbers of organisms aggregate and utilize it. The sheltered nature of

these areas also contribute to make them important as nurseries. Man-

grove areas thus export protein to coastal areas in the form of aquatic

organisms that use the mangrove areas for their early development and

then migrate offshore. Well known are the massive migrations of mullets

and shrimp from these areas. This is high quality protein that links man-

groves directly to other coastal systems like coral reefs , seagrass beds

and ultimately to man.

A preliminary analysis of published lists of the fish fauna of man-

grove areas in Florida (USA) , the Caribbean and Brazil shows that there

are more than 275 species of fish belonging to 66 families that are in

some way associated with mangrove areas- in these regions . Turner (197 7)

found a positive correlation between commercial yields of penaeid shrimp,

the area of intertidal vegetation and latitude. The predicted annual

yields per area of intertidal vegetation for the latitudinal range of 0-200

range from 39-159 kg/ha.

11. CLIMATIC CONSTRAINTS ON DEVELOPMENT

Mangroves do not necessarily need rain water, since they extract

fresh water from the sea, but the amount of rainfall influences the extent

of mangrove development in two ways. First, rainfall determines the

rates of soil weathering, erosion and transport, and thus the rate of

formation of deltas and other shallow coastal sedimentary features

Since these areas are the optimal substrate for mangrove growth, their

rate of formation can indirectly determine the extent of coastal man-

groves. Second, high temperatures, causing overall high evapotran

spiration rates in the tropics, would quickly lead to a salt build-up in

the inner parts of mangroves , if it were not for the flushing and leaching

of salts by rainwater. According to Macnae (1966, 1968), mangroves

develop best in Australia in areas receiving more than 2,500 mm/yr.

Below 1 500 mm/yr, salt flats begin to form.

Precipitation and evapotranspiratio

Rainfall in the Greater Caribbean is very low. Open sea areas

receive only 800-1000 mm/yr. However, because of the large amount

of solar radiation received at the surface there is a great deal of eva-

poration and moisture in the air. When the moisture laden air masses

are lifted against the slopes of an island there is condensation and

rainfall develops. The windward slopes of high islands are moist for

this reason. Convection due to heating of the island mass is another

important rain-producing mechanism. Since the land masses gain more

heat than the surrounding seas , convection cells and rainstorms develop

over the hot interior of islands often in the hot summer afternoons.

These rainfall producing mechanisms contribute more rain to the

interior of the larger islands than to the coast. Furthermore, the "leading

edge" of some islands can be drier than the "trailing edge" and the high

islands may have a "rain shadow" zone because of the adiabatic heating

of the subsiding air. Low and small islands get very little rain at all.

On low islands , and in the "rain shadow" side of the larger islands there

are commonly severe water deficits. During the year precipitation is

much less than potential evapotranspiration. Under these circumstances,

although there may be low areas influenced by salt water, mangroves may

be unable to colonize there, due to excessive salt accumulations. The

intense radiation turns these low flat areas into natural evaporation ponds.

Salt crusts form at the surface and interstitial salinities are much beyond

those tolerated by mangroves ( > 9051.).

Under these circumstances mangroves develop as a fringe, quite

often narrow, in which salinity levels are suitable. Because of the steep

salinity gradient inland the landward trees qLdckly become scrubby and

poorly developed. Between the swamp and higher ground one finds a

hypersaline lagoon (often containing dead or dying trees) and salt flats.

Therefore, both rainfall and topography influence the development

of basin and fringe forest types. Where precipitation is greater than

evapotranspiration basin forests are well developed. The interstitial

salinity in these basins is low and they may be dominated by the white

mangrove. Where precipitation levels are less than evapotranspiration

( < 1500 mm) basins begin to degrade until they disappear, giving way

to the formation of broad salt flats and shallow hypersaline lagoons. In

areas where precipitation is less than potential evapotranspiration soil

salinity becomes a dominant factor controlling the structural character-

istics of the forests . Because of the limited amplitude of the tide in

most of the Caribbean, high salt levels may be reached relatively short

distances from the edge of the fringe.

12. VULNERABILITY TO STRESSORS

A stressor may be defined as a condition that causes an energy

drain and a loss of potential energy that could be used to do useful work

in a system (Odum 19.67). The sustained operation of a stressor (a chronic

stressor) constitutes a constant energy drain and prevents the system from

attaining high levels of development. A stressor may also occur periodi-

cally, causing transient episodes during which maintenance costs are

increased. The resiliency of the system is its ability to respond to and

recover from a stressor.

Mangrove areas are subjected to natural and man induced stressors

both of which can impinge on the system in a chronic or acute mode. For

instance, hypersalinity can be a chronic natural stressor in many areas

of the Caribbean. Storms and droughts are examples of acute events.

Some pollutants can be chronic stressors in polluted areas, or behave as

acute stressors during a spill followed by effective cleanup. In general,

it is obvious that in a rigorous environment the structural development

of the forest will be arrested. In more optimum environments develop-

ment will proceed further until the structure is limited by site character-

istics such as nutrient availability, water tumover rate and climatic

limiting factors such as hurricane recurrence rates.

In the following section some natural and man induced stressors

are described and their impact on mangrove forests is discussed. The

reader is referred to Odum and Johannes' (1975) excellent review for

additional information.

12 .1 . Natural Stressors

12.1.1. Tropical cyclones

Cyclonic disturbances develop in the north Atlantic, Caribbean,

and Gulf of Mexico during the months of June thru November, although

they form outside of this "season" in rare instances. These cyclones

have high sustained winds , which near their center reach speeds that

range from 65 km/hr (40 mph) in a tropical depression to more than

119 km/hr (74 mph) in a hurricane. Mangroves are vulnerable to these

disturbances due to their coastal location, their shallow root system

(most of which is in the upper 30 cm of the soil) , the poor cohesiveness

or load bearing ability of most mangrove soils and their exposure to

waves , surge and erosion by strong water flows.

Wind speeds greater than 93 km/hr can cause defoliation and winds

in excess of 130-160 km/hr will bring down trees. Wadsworth and

Englerth (1959) reported that during hurricane Betsy in a black mangrove

forest in southern Puerto Rico, 59% of a sample of 62 trees had been

overthrown. The maximum reported wind.speed in San Juan, 21 km (13

miles) from the storm's center was 185 km/hr (115 mph). These trees

were 26 years old and had diameters (DBH) between 10 cm and 30 cm

(4 to 12 in). Black mangroves have very shallow root systems and lack

prop roots. The canopy structure also appears to influence this type

of forest's sensitivity to wind damage. Canopies of even height without

emergents and gaps are more resistant. Mature low density black man-

grove "orchard" forests appear to be very susceptible to windthrow.

Red mangrove forests , especially in exposed locations , develop

an extraordinarily complex and dense root supporting system. This

anchorage provides excellent protection from windthrow. Upright

(straight'bole) trees are only found inland in sheltered locations. At

the fringes , however, wave scour may be a more severe problem than
wind. High wind speeds also cause extreme flexing of the stems and

separation of the bark from the woody tissue. Violent rubbing between

adjacent branches can cause girdling. Even if the tree is not defoliated

these branches will die and the trees will appear "burned" after the

storm. In an exposed location this type of damage will be more severe

in the windward part of the forest.

Stoddard (1969) recorded the damages to mangrove areas during

hurricane Hattie in British Honduras (Belize). HurTicane Hattie had winds

gusting to 322 km/hr (200 mph). In this area there was absolute devas-

tation within 1. 6 - 3.2 km (1 --n 2 miles) of the storm's track. The zone

of almost complete destruction extended to 32 km (20 miles). In that

zone, only small mangrove patches in the leeward portion of the largest

islands survived.

During storms large amounts of sand and other materials may be

dumped into the mangroves. The accumulation of these materials impairs

gaseous exchange thru lenticels and pneumatophores and may cause wide-

spread mortalities. Usually defoliation ensues within 3-4 weeks.

B$ftesen (1909) described an instance where large amounts of sand and

gravel were washed into Krausse's lagoon (St. Croix, U.S.V.I.) by the

hurricane of 1899. Before the hurricane, the lagoon contained many man-

grove islands with open water channels and bare flats. Dense R. mangle

forest occurred in the western landward side. After the storm, the

vegetation died and the wood was used as fuel for a nearby sugar-mill.

Craighead and Gilbert (1962) and Craighead (1964) have similarly de-

scribed post-hurricane mortalities due to marl deposition over roots in

the Ten Thousand Island area in Florida.

Storm waves in Puerto Rico during hurricane David (1979) uprooted

large tracts of seagrass beds in various areas. This material was

deposited in large quantities ashore. In southwestern Puerto Rico,

seagrass accumulations reached 2 m or more high in places, forming a

dike in front of the mangrove fringe. Large amounts were carried inside

the mangroves. These inordinate accumulations have caused dieoffs in

the mangrove because of smoothering and restrictions in tidal exchange,

leading to hypersaline conditions. Tabb. and jones.(19.62) report similar

occurrences in North Florida Bay as a result of Hurricane Donna.

When fringe trees die but remain standing they eventually lose

their aerial roots and the associated root community (Tabb et al. 1962).

In exposed locations whole cays and fringes may be scoured away by

waves. Large boulders and limestone blocks were deposited by waves

in some mangrove covered coral islands in southwestern Puerto Rico by

Hurricane David. In Cayo Turrumote a boulder rampart 0.5-1 m in height

was deposited against the mangrove forest. Recovery is determined by

the after storm configuration of the coasts . In places sediment deposition

may raise the level of the soil so much that the area cannot be success-

fully recolonized by mangroves. In other areas shoals and other

structures may have been formed and become available for establishment.

Recolonization is slow but ultimately the newly formed banks and shores

become stabilized by seagrasses and mangroves, starting the forest

development cycle anew. Forest development during the first years is

slow and is a function of seed availability. The edges of channels and

shorelines quickly develop thickets. The inner parts of the swamps

usually develop more slowly since the entry of seedlings is impaired by

debris and standing dead trees.
-Alexa-ndter (19:6.7.) reported -that extensiIve flooding by salt water

(salinity 300Q during Hurricane Betsy caused severe plant kills (scorching)

of non-salt tolerant species in the southeastern Everglades. The damage

was..increa.sed..by, impounding ciaus.ed by man made dike.s. The -surface

waters freshened slowly after the storm, taking about two months to re-

vert to normal values.

12.1.2. Tidal waves

Tidal waves are not frequent in the Caribbean but these destructive

waves are known to have caused widespread damage in the past to low

lying coastal areas. In 1946, a tidal wave destroyed a large mangrove

forest situated at the head of Bahla de Samand in the Dominican Republic

(Sachtler 1973). It is estimated that 4500 ha of a total of 6500 ha were

destroyed. The surviving stands were those of black mangroves found in

the innermost portions of the swamp.

The area recovered from this event rapidly. Presently basal area

and density (for stems > 2.5 DBH) in the R. mangle stands are

between 17.5-21.5 m2/ha and 463-714 stems/lia , respectively. Mean

diameter of the stand for this even aged forest (now 36 years old) is

between 19. 6 and 21.9 cm (Cintr6n and Alvarez, unpublished).

12.1.3. Eustatic sea level rise and coastal erosion

Sea level is presently rising at the rate of 30 cm/l 00 years. This

marine transgression has favored the expansion of mangroves over areas

previously occupied by terrestrial plants. There is little doubt that this

has induced a regressive movement in the seaward margin of mangroves

in many areas. Hoffmeister (1974) reports the erosion of a rock pavement

of fossilized roots of black mangroves in Florida. Zieman (1972) has .

found circular beds of Thalassia testudinium growing over red mangrove

peats. These peats were deposited in hammocks which were submerged

by the sea level'rise.-'Extensiv e areas within Card Sound (Florida) show-,

severe fringe erosion. The shallow banks in front of the mangrove fringes

are sand - or seagrass - veneered red mangrove peat deposits. In Pue rto

Rico, peat areas are found on the bottom of shallow embayments overlain

by sand. In Bahfa de Samand (D.R.) there is serious erosion of the fringe

in considerable segments of the mangrove-lined bayhead shoreline.

12.1.4. Hypersalinity

As discussed earlier, hypersalinity is a chronic stressor in most

coastal areas of the Caribbean and is one of the dominant factors con-

trolling the structural characteristics of these forests. Carter et al.

(1973), Burns (1976), Hicks and Burns (1975), and Lugo et al. (1975)

have demonstrated that there are increases in respiration and decreases

in net productivity with increases in soil salinity. The higher mainte-

nance costs are also associated with stunting. As interstitial salinities

increase the canopy height decreases (Cintr6n et al. 1978, Fig. 1). The

diameter of the trees also decreases as well as basal area , wood volume

and complexity index (Mar-ffnez et al. 198 1).

The control that salinity exerts over the physiographic character-

istics of astand in an arid environment is exemplified by some mangrove

islands on the south coast of Puerto Rico (Cintr6n et al. 1975, 1978).

The development of a mangrove island over time is shown schematically

in figure 2. Initially mangroves colonize shallow banks, expanding

laterally over them. The growth of the trees at the outer margins is more

vigorous and these trees may attain greater heights . Circulation to the

inner parts of the island may be reduced by active growth at the margins.

Red mangroves in the core are replaced in time by black mangroves as

salinities increase. If soil salinities remain high but stable an island

will develop an outer ring of red mangroves and an inner core of well

developed black mangroves. Where salinities are too high the core will

consist of dwarfed blacks. If circulation is further restricted there will

be a dieoff at the core leaving an annular island with a hypersaline

lagoon as in step 5 of figure 2.

Wave flushing at the windward edge of the island allows the red

mangrove fringe to be thicker than on the protected side of the island

(Fig. 3). In fact, where there is unimpaired circulation the island may

remain in stage I or 2 indefinitely. The maturation process takes place

in the islands in more sheltered localities.

Fringes may also suffer from a similar aging process. In time

extensive areas of the inner swamp die and shallow lagoons and salt

flats are formed. These diebacks occur following periods of drought.

In dry regions, mangrove areas may be unstable with coverage fluctuating

between periods of expansion (usually following storms or a succession

of very wet years) and contraction (usually triggered by a succession of

dry years). In very dry areas, basins may disappear- altogether leaving

only a thin red mangrove fringe backed by shallow bare hypersaline

lagoons and salt flats.

These areas of dead mangroves are a common feature in dry coast-

lines. Bacon (1970) described the "Red Swamp," situated between the

Blue and Caroni Rivers in Trinidad. Examination of aerial photographs

taken between 1942 and 1966 showed a gradual expansion of the dead

areas. Reclamation work in the region may have been responsible for

accelerating this dieoff by interfering with water movements.

Servant et al. (1978) report the characteristics of one of these

hypersaline areas on the islet of Fajou in Guadeloupe. This area is

separated by a porous bar from the sea. Seawater penetrates the basin

and evaporates , concentrating salts within. Salinities are reduced

transiently during episodes of heavy seas when water washes into the

basin or when heavy rains leach some of the salts away. This stressful

cycle is a common feature of many shallow hypersaline lagoons in the

Caribbean area. In most of these and areas the system is delicately

poised and man's intervention by reducing water flows or impounding

areas by structures such as causeways and roads often exarcebates
'A
these naturally occurring stressful conditions causing mortalities too.

12.2. Man Induced Stressors

12.2. 1. Channelization, diversion of fresh water

Channelization and fresh water diversion schemes are extremely

damaging. Mangroves are open systems and require continuous nutrient

inputs to maintain their high rates of productivity and other ecosystem

processes. Furthermore, in and areas reduction of fresh water input

quickly results in the onset of hypersaline conditions and mangrove

dieoff.

12.2.2. -Impoundment

Impoundment is another stressor that leads to rapid deterioration

and death of mangrove areas. Diking cuts off mangroves from nutrient

flows' it may raise water levels or lengthen the hydroperiod, causing

the lenticels and pneumatophores to-become covered with water. This

impairs or stops gas exchange. In other instances lowering water levels

or reducing flows causes salinity to increase rapidly as salt water

eva pora te s .

In 1965, the Department of Agriculture of Puerto Rico built a dike

impounding a 177 ha mangrove stand and flooding it to a I m depth. The

purpose was to artificially create a habitat for wading birds. A massive

dieoff followed immediately. The area had contained an extensive and

well developed black mangrove forest (DBH^- 10 cm). Only those trees

on higher ground survived and then did so by producing extremely long

pneumatophores (36.1 cm � 0.5 as against 10-15 cm in normally flooded

areas) . There has been very limited natural restoration of the area. The

dikes restrict tidal flushing so that during the dry season the impounded

area dries up. The loss of the canopy exposes the impounded water and

soil to the sun and extreme overheating during the dry season. Dissolved

oxygen in the heated surface water (temperature > 30tO C). drops below.

0. 5 mg/L.

White mangroves have recolonized some areas by becoming estab-

lished over the stumps of fallen trees., The water depth reached during

the wet season appears to limit the areas that can be colonized by man-

groves.

Impoundment can also occur when roads are built through mangrove

basins if.care is not taken to preserve water flows. Patterson-Zucca

(1978) has described the impact of road building on a mangrove swamp.

M
In St. Thomas I construction of a road near Compass Point isolated and

killed a small mangrove area. Hypersalinity may have been the cause of

that dieoff.

12.2.3. Sedimentation

Mangroves are adapted to high sedimentation environments, but

sudden deposition of large quantities of sediments can cause mortality.

Under natural conditions , excessive sedimentation occurs as a result of

catastrophic penomena like storm generated waves or floods. Man,

however, is often the cause of severe sedimentation problems in some

mangrove areas. Cintr6n and Pool (1976) reported that sand extraction

from a coastal dune for airport construction reduced the dune height

from 12 m to only 3m. During 1967, storm waves overwashed the

residual dune, carrying large amounts of sand into a mangrove forest.

Sand deposition varied from more than one meter to a thin sand veneer

more. than. 260 m, inland.. All*the mangroves, were killed where sand

deposits were higher than 30 cm, and some trees died where the sedi-

ment depth was between 20 and 3'0 cm. The area covered by the sand

wedge has been colonized by Australian. pine (Casuarina equisetifolia).

Kolehmainen (cited by Odum and Johannes , 1975) noted an area in

Puerto Rico where fibrous waste from a sugar mill escaped from settling

ponds and killed most of the trees in a black mangrove QL. germinans)

stand.

Deposition of dredge spoils into mangrove areas will also cause

large scale mangrove mortalities. During the late 1960's , dredged

material was discharged into the Punta Picda penninsula on the north

coast of Puerto Rico., causing the total d.estruction.of a large. mangrove

tract. This area too has been extensively colonized by Australian pine.

Deforestation and loss of soil can increase the rate of sedimenta-

tion in low lying swamps, causing shallow lagoons to become salt flats

and killing inner swamp trees.

12.2.4. Thermal pollution

In shallow stagnant areas water temperatures may reach more than

430 C (1100 F) . These areas are not reseeded since temperatures may

be limiting (Craighead 1964). McMillan (1971) reported that temperatures
of, 39-14-00, C' for 418'.hlours.' ca-us, ed'd elat@h o f-I rooted but s1te' mless A . germinan s

seedlings.

The cooling water plumes from electric generating plants often

approach.thi -temperature. In Puerto Rico, Banus and Kolehmainen. (197.6)

ha ve suggested that temperatures above 380 C (1000 F) define the begin-

ning of deterioration of mangrove trees. These stressed trees have small

leaves (Lugo and Cintr6n, 1975), are partially defoliated (only terminal

leaves remain) , chlorotic and produce dwarfed seedlings. The mangrove

root community is much more sensitive to high temperatures than the

mangrove trees (Kolehmainen et al. 1974). The species composition and

biomass of mangrove root communities was unaffected by temperatures

below 340 C (930 F). Between Wand 350 C (93 and 950 F) the number of

species decreased abruptly, and above 350 C (950 F) the number of species

was inversely related to the water temperature. At higher temperatures ,

37.5-39.70.C (99.5-103.50 F) , blue green algae.became common, forming

floating mats in the water surface.

12.2.5. Oil

Mangroves are extremely sensitive to oil pollution because of

fouling of the gas exchange surfaces. Heavy coating of the intertidal

root region or pneumatophores invariably causes death of the trees. In

addition to acting as a mechanical barrier oil contains soluble toxic

fractions. These compounds can be toxic to the roots and to the microbial

populations in the soil.

The initial response of mangroves exposed to severe oil fouling

appears to be defoliation. Defoliation may be partial or total, depending

on the amount of oil remaining in the roots and substrate. Following the

Peck Slip oil spill in eastern Puerto Rico, the heavily impacted areas lost

50% of the canopy in 43 days and 90% after 85 days (Cintr6n et al. 1981).

Total loss of the canopy was irreversible in the oil stressed red mangroves.

In the marginal areas where the trees were exposed to sublethal amounts

of oil defoliation was followed by production of smaller, often deformed,

new leaves.

Lugo et al. (1981) have suggested that different forest types exhibit

different susceptibility to oil pollution. For instance , riverine forests

appear to be least vulnerable to oil pollution since the surface fresh-

water flows move the oil slicks away. Oil spilled in the ocean has little

chance of entering the river mouth since salt water enters as a bottom

flow. The greatest vulnerability for this forest type would occur during

the dry season when surface flows are reduced or if the spill occurs up

river or inside the estuary. In exposed locations, sand bars formed in

front of river mouths can hinder oil penetration.

Basin mangroves are most susceptible to stressors that originate

inland and therefore are less vulnerable to seaborne oil. Often (but not

always) basins are isolated from fringes by berm. Basins are most

vulnerable during periods of spring tides. They can be severely impacted

by spills that originate from inland facilities and pipelines. Since oil

would be retained for a long time in a basin its effects would be devas-

ta ting -

Fringe and overwash forests are the most vulnerable to seaborne

oil. Oil enters the fringe and accumulates inside. In the outer edge of

the fringe water motion assists in cleansing the root surfaces. For this

reason, there may not be any-defoliation of the trees in the outer edge

and complete canopy loss inside. In very sheltered locations, however,

defoliation may be total.

Presently, there are no practical means to remove oil from man-

grove areas . For this reason, it is imperative to prevent the entry of

oil by using booms and sorbent barriers. Oil tends to penetrate into the

porous mangrove sediments'and persist for very long time periods.

Residual amounts of oil are still found in Bahra Sucia in southwestern

Puerto Rico after a spill that occurred in 1973. In areas in which there

are high rates of water exchange oil is leached out and seedlings are

brought in so that recuperation from an acute event occurs quickly.

Where large residual amounts of oil persist recovery may be considerably

delayed. In fact, residual amounts of oil may impede the reestablish-

ment of a well developed stand.

The "successful" establishment of red mangrove seedlings in an

area impacted by oil does not mean that the site is on its way to recu-

peration. Red mangrove seedlings are very tolerant to stressors but this

tolerance decreases as the plant develops and requires more from the

external environment rather than from its ample storages, This indepen-

dence is prolonged by the slow growth rate of the seedlings (0. 4 - 0. 5

cm/mo during the first months). This, and the continual replacement

of dead seedlings by new arrivals gives the false impression that natural

regeneration is occurring. It seems however, that when significants

amounts of oil remain in the sediment, seedlings dieoff as their initial

high tolerance decreases. The development of saplings into mature

trees may be dependent upon the rage at which oil is leached or degrad4d.

12.2.6. Mining

There are no known mining activities currently occurring in man-

grove areas of the Caribbean. The energy crisis has pressed considera-

tion of the use of peats as energy sources and mining of these peats has

been contemplated in the Negril's Great Morass in Jamaica.

In Puerto Rico, sand was mined from mangrove lined coastal lagoons

during the 1960's. This activity created pits 18 m deep in places in

lagoons whose original depth was only 1-2 m. These pits trap saline

water and are depositional basins for organic sediments with high oxygen

demands. As a result, the pits are persistently anoxic below 2 m, the

BOD5 in the bottom waters often exceeds 200 mg/L and NH4 as (N) may

be in excess of 15 mg/L (Ellis 1976).

13. RECOVERY

Natural ecosystems have growth strategies and adaptations that

allow them to recover from periodic natural perturbations . Because of

this inherent resiliency ecosystems will restore themselves sponta
neou-sly once the disturbance has subsided. Assuming that there are no

residual effects left by the stressor(s) an ecosystem will normally revert

to a state very similar to its pre-stressed condition. Under the influence

*of residua:1 stressors and/or an. increase'.d. necurrence rate of.acute events

the system will only achieve a simpler Ieve I of organization (Odum 1981)

In general, then, human intervention in the restoration process

could be limited'to removing the'stressor that is causing the degradation

and allowing the system to restore itself. It is wasteful and useless to

attempt to restore areas artificially if the stressor has not been removed

or residual amounts are left.

In the case of mangroves, the rate of recovery in a benign environ-

ment is a function of the size and proximity to seed sources. The

conservation of ample seed stocks insures quick and natural regenera-

tion with minimal human intervention.

In some areas , it may be desirable to accelerate the recovery of

a stand by preparing the terrain and insuring an even distribution of

seedlings by planting. Pulver (1976) gives some preliminary guidelines

for the transplant of saplings (0.5-1.5 m in height). Planting saplings,

however, is more difficult and costly than planting seedlings and the

saplings must be removed from natural stands. The following points

should be considered before artificial restoration is attempted:

Select candidate sites. carefully.. If the area has contained

mangroves before, determine the cause of loss and make

sure the stressor has been removed. Naturally, "blank"

areas may be hypersaline or too elevated for successful

.-.establishment.

Because of the ease of handling and planting, red mangroves

are one.of the -mos.t. suitable species for riestoration'.projects

but they may not always be appropriate. The selection of

the species to plant should be made on the basis of the

dominant species at nearby locations having similar eleva-

tion, hydroperiods and exposure.

Soil elevation should be low enough that the area is

frequently flooded by tidal water, and there is adequate

circulation. Stagnant areas tend to overheat.

Measure interstitial (soil) salinities. Areas with inter-

stitial salinities above 55%, are not suitable for restoration

by red mangroves.

Areas must be sheltered from wave action and current

scour.

Remove dead standing wood and clean-up the area. Floating

or falling debris will uproot and damage planted seedlings.

Control the spacing of seedlings, Dense plantings result
in stagnation' (slow growth) due to excessive c.ompetition.

For Rhizophora sp. the recommended spacing for seedlings

is 0.6-1.2 m (Watson 1928).

Recently, fallen seeds-may be collected from nearby man-

grove areas or they may be collected from trees. Use only

ripe seeds. For red mangrove, use those. seeds in which

the abscission layer has developed (these are easily

detached from the parent tree). Select healthy seeds and

discard malformed or damaged propagules. Maintain the

collected material wet and avoid exposing it to overheating

during transportation and before planting. Seeds can be
carried in an inexpensive 'foam icebox or a wet burlap sack.

Red mangrove seedlings should not be inserted too deeply

in the..substrate.. The seed should be planted deep enough

so that it will not fall over (Watson 1928). For a 20-30 cm

seedlings the planting depth should be 4-7 cm.

Since initial growth rates and mortality of red mangrove seedlings

are very low it is impossible to judge the success of a restoration

h's observations . The restored area
pro-ject on the basis of a few mont

should be checked annually to replace dead saplings and/or remove

unwanted new arrivals.

14. -CONCLUSION: - CONSERVATI.ON NEEDS

Island coastal marine ecosystems are in jeopardy in many areas of

the Caribbean, due to high populations, mounting pressures to develop,

a limited land base, and inadequate impact assessment procedures.

In..the smaller. i.slands inland-and.coa$tal ecosystems are intimately-

linked. Inland activities like deforestation, agriculture on steep slopes ,

raising of domestic animals , road building and many others can increase

sediment levels in estuarine and coastal waters , contributing to the

degradation of coastal ecosystems. Protection of the marine resources

depends on developing land use practices that will not impair the

productivity of mangroves, seagrass beds and coral reefs .

Society derives direct benefits from the conservation of these

coastal ecosystems. They are part of the resource base upon which

islands depend. There are very practical reasons for their conservation,

including the products they yield (fisheries) and their role in protecting

the coasts from storm damage, as well as their more intangible values.

Tourism, an important source of income, can be developed to take

advantage of their uniqueness and great beauty. Natural reserves or

parks can be established to protect especially important areas; these

attract local. as well as international tourism and also stimulate

scientific research, all of which benefit the local economy. They are

valuable educational assets.

On a more modest scale small projects can be developed to take

advantage of areas of particular s-cenic beauty.. This kind of project,

when designed for mangroves , 'need's to take into account the fact that

mangrove areas are naturally prone to flooding; structures built in these

areas are susceptible to recurrent damage by flood waters and storms

unless they are'constructed with flooding.in mind. Because of -the

danger of storms, no permanent population centers should be encouraged

to develop in mangroves , 'since the occupants would alway's be at risk.

In summary, mangroves are among the most productive coastal

ecosystems known to science. In addition to their aesthetic and

recreational values, they form an important part of the economic resource

base of Caribbean islands because of their intimate ties to coastal

fisheries, seagrass beds and coral reefs. In many areas they still

evoke negative reactions , because of a lack of understanding of their

importance. Though highly resilient in the face of natural stressors ,

mangrove forests are extremely vulnerable to many stressors caused by

human activity,. including sedimentation, channelization, diking, drain-

ing, and many kinds of pollution. An understanding of their role in

coastal protection and the nurture of fish and wildlife should lead to

more enlightened mangrove management practices throughout the

Caribbean.

15. BIBLIOGRAPHY

Alexander, T. R. 1967. Effects of Hurricane Betsy on the southeastern
Everglades. Quart. J. Fla. Acad. Sci. 30(l):10-24.

Bacon, P. R. 1970. The Ecology of Caroni Swamp, Trinidad. Central
Statistical Office, Trinidad. .68 pp.

Banus, M., and S. W. Kolehmainen. 1976. Rooting and growth of red
mangrove seedlings from thermally- stressed tress. Pp. 46-53.
In: G. W. Esch and R. W. McFarland (Eds) Thermal Ecology II.
CONF 750425 Technical Information Center ERDA Springfield, Va.

Bird , E. C. F. 1976. Coasts. An introduction to systematic geomor-
phology, volume 4, Australian National University Press
Canberra, 282 p.

B$@ergesen, F. 1909. Notes on the shore vegetation of the Danish West
Indian Islands. Bot. Tidsskr. 29:201-59.

Burkholder, P. R. , L. M. Burkholder, and L. R. Almod6var. 1967.
Carbon assimilation of marine flagellate blooms in neritic waters
of southern Puerto Rico. Bull. Marine Sci. 17(l):1-15.

Burns , L. A. 1976. A model of mangrove ecosystems , rationale, data
analysis, and model formulation. pp. 53-84. In: H. T. Odum
(Ed) Guidelines for management of mangroves in south Florida.
Contract No. 14-1610004-426. Final Report to U.S . Dept. of
the Interior. Center for Wetlands , Univ. of Fla. Gainesville, Fla.

Carter, M. R. , L. A. Bums, T. R. Cavinder, K. R. Dugger, P. L. Fore,
D. B. Hicks, H. L. Revells, and T. W. Schmidt. 1973. Eco-
systems analysis of Big Cypress Swamp and estuaries. EPA
904/9-74-002, U. S. Environmental Protection Agency, Region IV,
Atlanta. 478 pp.

Cintr6n, G. , A. E. Lugo, D. J. Pool, and G. Morris. 1975. Los man-
glares de las costas 6ridas.de Puerto Rico e islas adyacentes.
Memorias del Segundo Simposio Latinoamericano sobre Oceanografra
Biol6gica. Universidad de Oriente, Cumancl Venezuela. 2:137-150.

Cintr6n, G. and D. T. Pool. 1976. Efectos de la deposici6n de arena e
inundaci6n en un manglar en'Puerto Rico. Tercer Simposio Latino-
americano de Oceanograffa Biol6gica. San Salvador, El Salvador.

Cintr6n, G. A. E. Lugo, D. 1. Pool, and G. Morris. 1978. Mangroves
of and e.nviron-ments.-in..Puerto Rico and adjacent islands i@ Bio--.- - --
-tr6pica 10(2):110-121.

Cintr6n, G. , A. E. Lugo, and R. Martfnez. 1980. Structural and
functional properties of mangrove forests. A Symposium Signaling
the Completion of the ."Flora of Panama , " University of Panama.
To be published in: Monographs in Systematic Botany, Missouri
Botanical Garden..

Cintr6n, G. C. Goenaga, andA. E. Lugo. .1980a. Observaciones
sobre la ecologfa de las franjas de manglar en zonas dridas.
Memorias del seminario sobre el estudio cientifico e impacto
humano en el'ecosistema d.e manglares. UNESCO, Montevideo.
405 p.

Cintr6n, G. , A. E. Lugo, R. Martfnez, B. B. Cintr6n, and L. Encamaci6n.
1981. Impact of oil in the tropical marine environment. Technical
Publication, Division of Marine Resources, Dept. of Natural
Resources of Puerto Rico.

Cintr6n, G. and Y. Schaeffer-Novelli. 1981. Introducci6n a la ecologfa
del manglar. Seminario sobre ordenaci6n y desarrollo integral de
las zonas costeras, Guayaquil, Ecuador, 18-27 May 1981. 20 p.
EC/80/006.

Craighead, F. C. 1964. Land, mangroves, and hurricanes. Fairchild
Trop. Garden Bull. 19:5-32.

Craighead, F. C. and V. C. Gilbert. 1962. The effects of Hurricane
Donna on the vegetation of southern Florida. Quart. 1. Fla. Acad.
Sci 2 5:1-28.

Cundel, A. M., M. S. Brown, R. Stanford, and R. Mitchell. 1979.
Microbial degradation of Rhizophora mangle leaves immersed in
the sea. Estuarine and Coastal Marine Science, 9:281-286.

Davis H. 1940. The ecology and geologic role of mangroves in
Florida. Carnegie Inst. Washington Pub. 517:303-412.

Ellis , S. R. 1976. History of dredging and filling of lagoons in the
San Tuan Area, Puerto Rico. U . S. Geological.Survey, Water
Resources Investigations 38-76. U. S.G.S. Ft. Buchanan,
P. R. 25 p.

Etkins., R. and E. S. Epstein. 1982. The rise of global mean sea level
:.. . . I as -an indication- of -climatic change... Science 215(453-0):287@289-._

Febvay, G. and A. Kermarrec. 1978. Formation de la litiere en foret
littorale et en foret de montagne humide. Bulletin de Liaison du
Groupe de Travail, Mangroves et Zones Cotiere, Guadeloupe,
4:7 9-80.

Gill, A. M..and P. B. Tomlins. on.. 1977.. Studies on the growth of the
red mangrove (Rhizophora mangle L.). 4. The adult root system.
Biotr6pica, 9(3):145-155.

Hicks, D. B. and L. A Burns . 1975. Mangrove metabolic response
to alterations of natural freshwater drainage to southwestern
Florida estuaries. Pp. 238-255. In: G. E. Walsh, S. C. Snedaker,
a nd H. 1. Teas (Eds). Proc. of the International Symposium on
Biology and Management of Mangroves. East-West Center,
Honolulu, Hawaii.

Hoffmeister, 1. E. 1974. Land from the sea. University of Miami Press ,
Coral Gables, Fla. 143 p.

Kolehmainen, S. E., T. 0. Morgan, and R. Castro. 1974. Mangrove
root communities in a thermally altered area in Guayanilla Bay,
Puerto Rico. Pp. 371-390. In: T. W. Gibbons and R. R. Scharitz
(Eds) Thermal Ecology. CONF. 730505. U. S. AEC. Augusta, Ga.

Lugo, A. E. and S. C. Snedaker. 1974. The ecology of mangroves.
Ann. Rev. Ecology & Systematics 5:39-64.

Lugo.,.A. E. and G. Cintr6n. 1975. The.mangrove forests of Puerto Rico
A and their management. Pp. 825-846. In: G. E. Walsh, S. C.
Snedaker, and H. J. Teas (Eds). Proc. of the International
Symposium on Biology and Management of Mangroves. East-West
Center, Honolulu, Hawaii.

Lugo, A. E. , G. Evink, M. M. Brinson, A. Broce, and S. S. Snedaker.
1975. Diurnal rates of photosynthesis , respiration, and transpira-
tion in mangrove forests of Florida. Pp. 335-350. In: F. B.
Golley and E. Medina (Eds). Tropical Ecological Systems ,
Springer-Verlag, N. Y.

Lugo, A. E. , G. Cintr6n, and C. Goenaga. 1981. Mangrove ecosystems
under stress. Pp. 129-153. In: G. W. Barrett and R. Rosemberg
(Eds). Stress Effects on Natural Ecosystems - Tohn Wiley & Sons
Ltd

Macnae, W. 1966. Mangroves in eastern and southern Australia.
Austral. J... Bot.. 14:67-,104...

Macnae, W. 1968. A general account of the fauna and flora of man-
grove swamps and forests in the Indo-West-Pacific region.
Advances Marine Biol. 6:73-270.

Martfhez, R., L. Encarnaci6n, G. Cintr6n, L. Cruz, and M. Aponte.
1981. Cara cter:rs tica s.estructurales de los manglares de Puerto
Rico. Proceedings VII Simposio Latinoamericano sobre Oceano-
gra ffa Biol6gica. 15-19 Nov.. 1981, Acapulco, Mexico.

McMillan, C. 1971. Environmental factors affecting seedling
establishment of the black mangrove on the central Texas coast.
Ecology 52:927-30.

Negr6n, L. N. 1980. La producci6n de hojarasca en el manglar ribe-
reho del Espiritu Santo. M.S. thesis, Univ. of Puerto Rico,
Rio Piedras, P. R. 73 pp.

Negr6n, L. and G. Cintr6n. 1981. Estructura y funci6n del manglar
de Laguna Toyuda, Mayaguez, Puerto Rico. Proceedings VII
Simposio Latinoamericano sobre Oceanograffa Biol6gica, 15-19
Nov. 1981 ,Acapulco, Mexico.

Odum, E. P. 1981. The effects of stress on the trajectory of ecological
succession. Pp. 43-47. In: G. W. Barrett and R. Rosemberg
(eds) , Stress Effects on Natural Ecosystems. Tohn Wiley & Sons
Ltd .

Odum, H. T. 1967. Work circuits and systems stress. Pp. 81-138.
In: Symposium on Primary Productivity and Mineral Cycling in
Natural Ecosystems (H.E. Young Ed.). Univ. of Maine Press.
Orono, Maine.

Odum, W. E., and R. E. Tohannes. 1975. The response of mangroves
to man induced environmental stress. Pp. 52-62. In: E.
Ferguson Wood and R. E. Tohannes (Eds), Tropical Marine
Pollution. Elsevier Oceanography Series, Amsterdam, Netherlands.

Patterson-Zucca, C. 1978. The effects of road construction on a man-
grove ecosystem. - M.S. thesis, Univ. of Puerto Rico, Rfo Piedras
P. R. 77 pp.

Pool, D.. A.. E. Lugo, and S. C. Snedaker. 1975. Litter production
in mangrove forests of, s outhern -Florida and Puerto Rico.. Pp.. 213-.!237.
-In: G. E'. Walsh, S. C. Snedaker, and H. 1. Teas (Eds) , Proc.
of the International Symposium on Biology and Management of
Mangroves. East-West Center, Honolulu, Hawaii.

Prakash, A. 1971. Terrigenous organic matter and coastal phytoplankton
fertility. In: 1. D. Costlow (Ed) , Fertility of the Sea. Proc. Int.
SyMp.. Fertility Sea., Sao Paulo, Brasil. Gordon and Breach Science
Publishers, London and. New York.

Prakash, A. , M. S. Rashik, A. Jensen, and D. V. Subba Rao. 1973.
Influence of humic substances on the growth of marine phytoplankton:
Diatoms. Limnol. Oceanogr. 18:516-524.

Pulver, T. R. 1976. Transplant techniques for sapling mangrove trees,
Rhizophora mangle , Laguncularia racemosa , and Avicennia germinans ,
in Florida. Florida Marine Research Publications No. 22. Florida
D.N.R. Marine Research Laboratory, St. Petersburg, Florida. 14 pp.

Ryther, 1. H. 1969. Photo synthesis and fish production in the sea.
Science, 166:72-76.

Sachtler, M. 1973. Inventario y fomento de los recursos forestales:
Repilblica Dominicana, Inventario Forestal. PNUD/FAO FO:SF/DOM
8 Informe T6cnico 3. Roma.

Servant, 1. , N. lean-Bart, and 0. Sobesky. 1978. Le phenomene "Etang
Bois-Sec": Une zone d'hypersalure en mangrove. Bulletin de
Liaison du Groupe de Travail, Mangroves et Zones Cotiere,
Guadeloupe, r:,64-6.5.

Snedaker, S. C. and D. Pool. 1973. Mangrove forest types and bio-
mass. Pp. C-1 , C-13. In: The role of mangrove ecosystems in
the maintenance of environmental quality and a high productivity
of desirable fisheries . Final report to Bureau of Sport Fisheries and
Wildlife. Contract No. 14-16-008-606, Center for Aquatic Sciences.

Stoddart, D. R. 1969. Post-hurricane changes on the British Honduras
Reefs and Cays: Re-Survey of 1965. Atoll Res. Bull. 131:1-25.

Tabb , D. C. , D. L. Dubron, and R. B. Manning. 1962. The ecology
of morthern Florida Bay and adjacent- estuaries . Florida State
Board Conserv. Tech. Ser. Pub. No. 39. 81 pp.

Tabb, D. C. , and A. C. Jones. 1962. Effects of Hurricane Donna on
the aquatic fauna of North Florida Bay. Transactions of the
American Fisheries Society. 91(4):375-378.

Turnert E. R. 1977. Intertidal vegetation and commercial yields of
Penaeid shrimp. Transactions of the American Fisheries Society.
106(5):411-416.

Wadsworth, F. H. and G. H. Englerth. 1959. Effects of the 1956
hurricane on forests of Puerto Rico. Caribb. Forester 20:38-57.

Watson, 1. G. 1928. Mangrove forests of the Malay Peninsula.
Malayan Forest. Rec. 6:1-275.

Zieman, J. C. 1972. Origin of circular beds of Thalassia (Spermato-
phyta: Hydrocharitaceae) in south Biscayne Bay, Florida , and
their relationship to mangrove hammocks. Bull. Marine Sci.
Gulf Caribb. 22(3):559-574.

CT orcranic matter/m2.dav
Gross Net
Primary Total 24 hr Primary
Forest Type Productivity Respiration Productivity

Riverine 24.0 11.4 120 6

Basins 18.0 12.4 5.6

Fringes 13.2' 11.3 8.8

Hammocks 3.8 1.2 2.6

Dwarf 2.8 4.0 --

Table 1. Summary of primary productivity and respiration data
for different mangrove forest types. Based on Lugo
and Snedaker (1974) review.

0 SAN ILDEFONSO
Y= -0. 20 X + 16.58 0 PUERTO DEL MANGLAR
R2 0.72 (WET)
13 PUERTO DEL MANGLAR
(DRY)
.,&MAR NEGRO
e ISLAND 1.
BAHIA MONTALVA
0 ISLAND 2
10 BAHIA MONTALVA
MONA ISLAND
C30

0 00

0 30 40 50 60 70 80

SOIL SALINITY (0/00)

mangroves
Fig. 1 . Relationship between tree height and soil salinity in
of arid- coastlines of Puerto--Rico and adjacent islands (Cintr6n
et al., 1978).

I- INITIAL COLONIZATION
OF -OFF SHORE BANK

th-dut di rh
2- LATERAL GROWTH OVER
BANK

3- DEATH OF RHIZOPHORA AT
THE CORE'AN D'@ COLONIZATION
BY AVICENNIA
I R
3a-ALTEr"%"NATE STAGE AVICENNIA
GROWTH STUNTED. STUNTED OR
DEAD RHIZOPHORA AT CORE.

.4- ISLAND WITH STUNTED
AVICENNIA CORE.

5- MATURE ISLAND WITH
HYPERSALINE LAGOON.

Fig. 2. Conceptual scheme of mangrove succession for mangrove islands in
and coastlines (Cintr6n et al. 1978).
77-

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