[Federal Register Volume 65, Number 231 (Thursday, November 30, 2000)]
[Notices]
[Pages 71317-71321]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-30542]


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ENVIRONMENTAL PROTECTION AGENCY

[FRL-6909-8]


Water Quality Criteria: Notice of Ambient Aquatic Life Water 
Quality Criteria for Dissolved Oxygen (Saltwater): Cape Cod to Cape 
Hatteras

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of availability of ambient aquatic life water quality 
criteria for dissolved oxygen (saltwater): Cape Cod to Cape Hatteras.

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SUMMARY: Pursuant to section 304(a)(1) of the Clean Water Act (CWA), 
the Environmental Protection Agency announces the availability of the

[[Page 71318]]

completed document titled, Ambient Aquatic Life Water Quality Criteria 
for Dissolved Oxygen (Saltwater): Cape Cod to Cape Hatteras. The 
document contains EPA's recommended national 304(a) criteria for 
dissolved oxygen in saltwater to protect aquatic life. These water 
quality criteria recommendations apply to coastal waters (waters within 
the territorial seas, defined as within three miles from shore under 
section 502(8) of the CWA) of the Virginian Province (Cape Cod to Cape 
Hatteras). However, with appropriate modifications they may be 
applicable to coastal waters (as defined under section 502(8) of the 
CWA) in other provinces of the United States. Under the CWA, States, 
Territories, and Tribes are to adopt water quality criteria to protect 
designated uses. EPA has promulgated regulations to implement this 
requirement (see 40 CFR part 141). EPA's recommended water quality 
criteria do not substitute for the Act or regulations, nor is it a 
regulation itself. Thus, EPA's recommended water quality criteria do 
not impose legally-binding requirements. States, Territories, and 
authorized Tribes retain the discretion to adopt, where appropriate, 
other scientifically defensible water quality standards that differ 
from these recommendations. EPA may change these section 304(a) 
criteria recommendations in the future.
    Because these criteria were under development prior to the Agency's 
revision and implementation of its current processes for notice of data 
availability and criteria development (see Federal Register, December 
10, 1998, 63 FR 68354 and in the EPA document titled, National 
Recommended Water Quality--Correction EPA 822-Z-99-001, April 1999), 
and because EPA believes it is important to invite and consider public 
input in development of draft criteria, we enabled the public to submit 
significant scientific information and views to EPA (see Federal 
Register, January 19, 2000, 65 FR 2954) that might not have otherwise 
been identified during development of these criteria. EPA has reviewed 
the scientific information and views submitted by the public and has 
made revisions to the criteria where appropriate. Even though we are 
not required to respond to specific issues submitted by the public, we 
have provided a brief summary of some of the issues that lead to a 
revision, along with our response, in the section titled Supplementary 
Information.
    This document has been approved for publication by the Office of 
Science and Technology, Office of Water, U.S. Environmental Protection 
Agency. Mention of trade names or commercial products does not 
constitute endorsement or recommendation for use.

ADDRESSES: Copies of the complete document, titled: Ambient Aquatic 
Life Water Quality Criteria for Dissolved Oxygen (Saltwater): Cape Cod 
to Cape Hatteras can be obtained from EPA's National Service Center for 
Environmental Publications (NSCEP) 1-800-490-9198. Alternatively, the 
document and related fact sheet can be obtained from EPA's web site at 
http://www.epa.gov/waterscience/standards/dissolved/ on the Internet.

FOR FURTHER INFORMATION CONTACT: For questions regarding the 
development of the criteria contact Erik L. Winchester, USEPA, Health 
and Ecological Criteria Division (4304), Office of Science and 
Technology, 1200 Pennsylvania Avenue, NW., Washington, DC 20460; or 
call (202) 260-6107; fax (202) 260-1036; or e-mail 
[email protected]. For questions regarding implementation issues 
under State water quality standards programs contact Jim Keating, 
USEPA, Standards and Health Protection Division, (202) 260-3845; or 
email [email protected].

SUPPLEMENTARY INFORMATION:

Introduction

    Section 304(a)(2) of the CWA calls for information on the 
conditions necessary ``to restore and maintain biological integrity of 
all * * * waters, for the protection and propagation of shellfish, fish 
and wildlife, to allow recreational activities in and on the water, and 
to measure and classify water quality.'' EPA has not previously issued 
saltwater criteria for dissolved oxygen (DO) because, until recently, 
the available effects information was insufficient. This criteria 
document is the result of an extensive multi-year research effort to 
produce sufficient information to support the development of saltwater 
DO criteria. The water quality criteria presented in the document 
represent EPA's best estimates, based on the data available, of DO 
concentrations necessary to protect aquatic life and uses associated 
with aquatic life.

Overview of the Problem

    Hypoxia is defined in this document as the reduction of DO 
concentrations in water below air saturation. Oxygen is essential in 
aerobic organisms for the proper functioning of cellular processes. 
When hypoxia exists, organisms may get an insufficient amount of oxygen 
into their system which results in reduction in cellular energy and a 
subsequent loss of ion balance in cellular and circulatory fluids. If 
oxygen insufficiency persists, death will ultimately occur, although 
some aerobic animals also possess anaerobic metabolic pathways, which 
can delay lethality for short time periods (minutes to days). The 
animals most sensitive to hypoxia are those inhabiting well oxygenated 
environments which are not normally exposed to low DO levels. EPA's 
Environmental Monitoring and Assessment Program (EMAP) for the 
estuaries in the Virginian Province (defined as Cape Cod to Cape 
Hatteras) has shown that 25% of the area of the Province is exposed to 
some degree to DO concentrations less than 5 mg/L. Persistent DO levels 
below 5 mg/L can have an adverse effect on various life stages of 
aquatic organism. EMAP also has generated field observations that 
correlate many of the biologically degraded benthic areas with low DO 
in the lower water column. These two reports serve to emphasize that 
low DO (hypoxia) is a major concern within the Virginian Province. Even 
though hypoxia is a major concern for many waters, a strong technical 
basis for developing benchmarks for low DO effects has been lacking 
until recently.
    In the Virginian Province, hypoxia is essentially a warm water 
phenomenon. In the southern portions of the Province, such as the 
Chesapeake Bay and its tributaries, reduced DO may occur any time 
between May and October; in the more northern coastal and estuarine 
waters, it may occur at any time from late June into September. Hypoxic 
events can occur on seasonal or diel (daily) time scales. Seasonal 
hypoxia often develops as a consequence of water column stratification, 
which prevents mixing of well oxygenated surface water with deeper 
water. Diel cycles of hypoxia often occur in non-stratified shallow 
habitats where nighttime respiration temporarily depletes DO levels. 
Hypoxia may also persist more or less continuously over a season (with 
or without a cyclic component) or be episodic (i.e., of irregular 
occurrence and indefinite duration). The fauna most at risk from 
hypoxic exposure in the Virginian Province are primarily summer 
inhabitants of subpycnocline (i.e., bottom) waters.

Overview of the Protection Approach

    The approach to determine DO criteria to protect saltwater animals 
within the Virginian Province takes into account both continuous (i.e., 
persistent) and cyclic (e.g., diel, tidal, or episodic) exposures to 
low levels of DO.

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The continuous situation considers exposure durations of 24 hours or 
greater. Criteria for cyclic situations cover hypoxic exposures of less 
than 24 hours, but which may be repeated over a series of days. Both 
scenarios cover three areas of protection that are summarized here, and 
explained in more detail in the criteria document: (1) Protection for 
juvenile and adult survival; (2) Protection for chronic (growth) 
effects; and (3) Protection for larval recruitment effects (estimated 
with a generic recruitment model).
    The approach to derive these DO water quality criteria combines 
features of traditional water quality criteria with a new biological 
framework that uses a mathematical model to integrate time (replacing 
the concept of an averaging period) and establish protection limits for 
different life stages (i.e., larvae versus juveniles and adults). Where 
practical, data were selected and analyzed in manners consistent with 
the Guidelines for Deriving Numerical National Water Quality Criteria 
for the Protection of Aquatic Organisms and Their Uses (hereafter 
referred to as the Guidelines).
    The saltwater DO criteria segregate effects on juveniles and adults 
from those on larvae. The survival data on the sensitivity of the 
juveniles and adults are handled in a traditional Guidelines manner. To 
address cumulative effects of low DO on larval recruitment to the 
juvenile life stage (i.e., larval survival as a function of time), the 
new biological approach to deriving criteria uses a mathematical model 
that evaluates the effect of DO conditions on larvae by tracking 
intensity and duration of effects across the larval recruitment season. 
Protection for larvae of all species is provided by using toxicological 
data on the larval stages of nine sensitive aquatic organisms.
    The approach used to derive the new DO criteria deviates somewhat 
from EPA's traditional approach for toxic chemicals outlined in the 
Guidelines. However, where practical, data selection and analysis 
procedures are consistent with the Guidelines. Most of the terminology 
and the calculation procedures are the same, but one should consult the 
Guidelines for a more complete understanding of how these DO criteria 
were derived.
    The juvenile/adult survival and the growth criteria provide 
boundaries within which to judge the DO status of a given site. If the 
DO conditions are above the chronic growth criterion (4.8 mg/L), then 
this site would meet objectives for protection. If the DO conditions 
are below the juvenile/adult survival criterion (2.3 mg/L), then this 
site would not meet objectives for protection. When the DO conditions 
are between these two values, then the site would require evaluation 
using the larval recruitment model that integrates duration and 
intensity of hypoxia to determine suitability of habitat for the larval 
recruitment objective.
    The DO criteria are based entirely on laboratory findings. Field 
observations on the impact of low DO levels support the findings of 
laboratory studies. Field acute effects occurred in juvenile and adult 
animals at 2.0 mg/L, which would be predicted based on the 2.3 mg/L 
juvenile/adult criterion. In the field, behavioral effects generally 
occurred within the range where many of the laboratory sublethal 
effects occurred.

Revisions to the Draft Document

    Approximately half of the views and information submitted by the 
public on the draft DO criteria addressed science or technical issues, 
and the other half addressed implementation issues. EPA considered only 
the science issues when making revisions to the criteria. EPA will 
review the implementation issues when developing future implementation 
guidance. The more significant revisions due to science issues are 
summarized here.
    First, some commentors indicated that the larval recruitment model 
should not be based on the mud crab (Dyspanopeus sayi) alone. Based on 
further review of the toxicity information for other species, we have 
revised the dose-response curve in Figure 5 by using a final acute 
value (FAV) approach (see the Guidelines) to generate a new final 
larval survival curve that reflects responses of all nine species 
tested. Figures 5a and 5b have been replaced by a ``Final Larval 
Survival Curve'', and Figure 5c has been removed. These changes to the 
larval recruitment approach necessitated that changes also be made to 
Figures 6, 7, 12, 14 and 17. Overall, these changes had minimal effect 
on the criteria. The point (4.64 mg/L) at which the larval recruitment 
curve levels off in the revised criteria is only slightly greater than 
the point (4.45 mg/L) in the draft document.
    Second, some commentors raised issues about the effect that 
differences in larval life history requirements among species in the 
Virginian Province might have on the applicability of the larval 
recruitment model across species and regions in the Province. The 
consideration of all nine species in development of the larval 
recruitment model addresses this issue. Also, in an appendix we added 
an assessment of sensitivity that might be expected with the life 
history model parameters D (duration of larval development) and R 
(length of larval recruitment season). The sensitivity analysis was 
performed using the individual larval recruitment curve for the mud 
crab. The sensitivity of the model to these two parameters was 
evaluated by increasing or decreasing D while holding R constant, by 
holding L constant and increasing R, and varying both D and R at the 
same time. A range of values were chosen for this analysis that we 
believe encompass a reasonable range in species-specific larval life 
history requirements in the Virginian Province, and because the upper 
and lower ranges are relatively extreme values that can test the 
overall assumptions and sensitivity of the model. The results indicate 
that the DO curve associated with no greater than 5 percent cumulative 
impairment of seasonal larval recruitment is most sensitive to a 
simultaneous decrease in D and increase in R. Under these conditions, 
the protective DO value at 44 days (the length of mud crab larval 
development season) decreases. This evaluation shows that the model can 
easily be adjusted to account for latitudinal variations in life larval 
life history requirements, or even seasonal variations in timing of 
hypoxia events concurrent with larval development periods. The results 
also indicate the Virginia Province criteria are protective of most 
species under most conditions, but that in some site-specific 
situations they may be overprotective. In the absence of site-specific 
data that would suggest a lower level of DO may be acceptable, EPA 
believes that in order to ensure that most organisms and their uses are 
protected it is appropriate to derive Province-wide criteria that may 
be overprotective in some cases.
    Third, some commentors suggested that the 5 percent cumulative 
reduction in larval seasonal recruitment may be too low a protection 
goal. EPA disagrees. Larval life stages are important and this 
protection goal is meant to protect them at a critical point in their 
development and transition to the juvenile life stage, which for many 
species corresponds to times of the year when hypoxia conditions occur. 
We selected this Province-wide protection goal because it is consistent 
with the approach outlined in the 1985 Guidelines for deriving ambient 
aquatic life water quality criteria, because 5 percent is also 
consistent with the level of protection afforded to juvenile and adult 
life stages, and because, in absence of data that suggests otherwise, 
this level of reduced larval recruitment from DO alone is believed to 
be

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protective of most species. EPA recognizes that large losses of larval 
life stages occur naturally, and that many species may be able to 
withstand a greater than 5 percent loss of larvae, from low DO or 
otherwise, without an appreciable effect on juvenile recruitment. On 
the other hand, this may not be the case for certain highly sensitive 
species or populations that are already highly stressed, for example an 
endangered species. This may also not be the case where there are other 
important natural or anthropogenic stressors that contribute to a loss 
of the larval life stage. In such situations, it may be that a 5 
percent loss in larval recruitment from DO alone is not protective 
enough, and environmental risk managers may need to evaluate the 
Province-wide 5 percent protection goal in light of their site-specific 
factors that may contribute to a cumulative loss in seasonal larval 
recruitment. Also in response to this issue, an appendix was added to 
the document that shows, by using the mud crab as an example, how the 
larval recruitment criterion would change if the acceptable percentage 
impairment was increased. This example demonstrates the flexibility in 
the criteria approach and how one might change the protection goals on 
a site-specific basis should States and authorized Tribes choose to do 
so and have the data to support such a change, while still protecting 
designated uses. EPA believes the 5 percent cumulative reduction level 
in seasonal larval recruitment is appropriate and protective of 
populations in the Virginian Province in absence of data that suggest 
otherwise.

Implementation Overview

    Implementation of DO criteria may be slightly different from that 
of chemical toxicants, but not for reasons associated with either 
biological effects or exposure. The primary reason that DO might be 
implemented differently from toxic compounds is because controlling the 
effects of low DO is not accomplished by directly regulating DO. 
Rather, hypoxia is a symptom of a problem, not the direct problem. Thus 
DO would be regulated primarily through the control of nutrients (e.g., 
nitrogen and phosphorus) and oxygen demanding wastes. As a stressor, DO 
also differs from most toxic compounds in that there can be a large 
natural component to the cause of hypoxic conditions in any given water 
body.
    The DO criteria may also be appropriately used in a risk assessment 
framework. The criteria and management approach presented in the 
document could be used to compare DO conditions among areas and 
determine if DO conditions would be adequate to support aquatic life. 
Using the criteria, environmental managers could determine which sites 
need the most attention and what are the spatial and temporal extent of 
hypoxic problems from one year to the next. Environmental planners 
could also use the criteria in a risk assessment framework to evaluate 
how conditions would improve under different management scenarios, 
helping them make better management decisions.
    EPA recommends that States and authorized Tribes within the 
Virginian Province adopt numeric DO criteria for saltwater applicable 
at all times of the year for all marine waters designated for the 
protection of aquatic life or for waters whose existing uses include 
aquatic life. States and Tribes may adopt numeric criteria based on 
EPA's ambient water quality criteria for DO, such criteria modified to 
reflect site-specific conditions, or other scientifically defensible 
methods, 40 CFR 131.11(b)(1). States and Tribes should adopt narrative 
criteria where numeric criteria cannot be established or to supplement 
numeric criteria, 40 CFR 131.11(b)(2). Because EPA has issued 
recommended section 304(a) criteria for DO, numeric criteria for DO can 
be established. Numeric criteria for DO can be implemented in NPDES 
permits by determining the need for and calculating specific limits for 
oxygen demanding wastes and nutrients that spur excess algal growth and 
subsequent decay of aquatic plants. Such criteria also serve as a 
definitive benchmark for determining impairment of waters for Clean 
Water Act Section 303(d) listing purposes and then as a starting point 
for establishing TMDL's, wasteload allocations for point sources, and 
load allocations for nonpoint sources.
    To take full advantage of the flexibility allowed in the DO 
criteria methodology for determining specific protective DO levels, it 
is necessary to characterize both the diurnal and season patterns of DO 
concentrations in response to natural and anthropogenic pollutant 
loadings for the location where the criteria are applied. Simplified 
approaches to establishing protective criteria that ensure a level of 
protection consistent with the detailed approach outlined in the DO 
criteria document are acceptable. Any approach a State or Tribe chooses 
to use to implement the DO criteria must be reflected in the State's or 
Tribe's water quality standards and submitted to EPA for review and 
approval. To determine the scientific defensibility of a State's or 
Tribe's approach as part of the Clean Water Act section 303(c) review 
and approval/disapproval process, EPA will review information 
concerning the characterization of diurnal and seasonal patterns of DO 
concentration in relation to the geographic areas and the times of the 
year the criteria applies, and would want the State or Tribe to provide 
all of the data and information the State or Tribe relied on for its 
rationale.

Limitations of the Criteria

    These water quality criteria recommendations apply to coastal 
waters (waters within the territorial seas, defined as within three 
miles from shore under section 502(8) of the CWA) of the Virginian 
Province (southern Cape Cod, MA to Cape Hatteras, NC) of the Atlantic 
coast of the United States. The document provides the necessary 
information for environmental planners and regulators within the 
Virginian Province to address the question: are the DO conditions at a 
given site sufficient to protect coastal or estuarine aquatic life? The 
approach outlined in the document could be used to evaluate existing 
localized DO standards or management goals or establish new ones. The 
criteria do not address direct behavioral responses (i.e., avoidance) 
or the ecological consequences of behavioral responses, such as 
increased or decreased predation rates or altered community structure, 
nor do they address the issue of spatial significance of a DO problem. 
In addition, as with all criteria, these criteria do not account for 
changes in sensitivity to low DO that accompany other stresses, such as 
high temperature, extremes of salinity, or toxicants. Chief among these 
concerns would be high temperature because high temperature and low DO 
often appear together. Generally, low DO would be more lethal at water 
temperatures approaching the upper thermal limit for species. EPA 
believes the DO limits provided in the document are sufficiently 
protective under most conditions where aquatic organisms are not 
otherwise unduly stressed.
    Although the DO criteria for the Virginian Province may be over- or 
underprotective of aquatic life in other regions, the approach used to 
develop the criteria is considered to be applicable to other regions 
with appropriate regional modifications. Organism adaptations to lower 
oxygen requirements may have occurred in locations where oxygen 
concentrations have historically been reduced due to high temperatures, 
or in systems with non-anthropogenic high oxygen demand. Conversely, 
organisms in another region could be adapted to colder temperature and 
higher DO

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regimes than those covered in the document, and thus may have different 
sensitivity to DO concentrations. In addition, effects of hypoxia may 
vary latitudinally, or site-specifically, particularly as reproductive 
seasons determine exposure risks for sensitive early life stages. For 
these reasons, an environmental risk manager would need to carefully 
evaluate water quality and biological conditions within the specific 
location and decide if the Virginian Province criteria would apply or 
if region-or site-specific considerations would need to be made.

Endangered or Threatened Species Policy Recommendations

    When a threatened or endangered species occurs at a site and 
sufficient data are available to indicate that it is sensitive at 
concentrations above the recommended criteria, it would be appropriate 
to consider deriving site-specific DO criteria.

Future Implementation Information and Applications

    In the future additional information will be provided that will 
specifically address implementation issues. In the current document, 
implementation issues are discussed in a more general manner, 
summarizing important issues that environmental managers should 
consider in adopting and implementation of DO water quality standards. 
The future implementation information will provide more detailed 
discussion of implementation issues by using real world example data 
sets where possible, or hypothetical data sets that show users how to 
integrate their data and management goals. Application of this guidance 
to marine waters outside the Virginian Province may also be discussed. 
As a component of the implementation guidance, EPA originally 
envisioned publishing a visual basic-based computer program that would 
allow States and other users to derive DO criteria to meet the larval 
recruitment protection goal for coastal and estuarine animals. However, 
the recent revisions in the criteria (i.e., the use of multiple species 
in the larval recruitment model) has precluded use of the visual basic 
model in its current format. Therefore, the model when available will 
likely be provided as a spreadsheet application compatible with 
commonly used software packages. EPA anticipates providing the 
additional implementation guidance in late 2001.
    EPA believes the approach used to develop the criteria can be 
applied, with minor modifications and regional specific data, to derive 
DO criteria for other coastal and estuarine regions of the United 
States. Therefore, in the future EPA plans to prepare similar DO 
criteria for other provinces based on this approach. At such time, EPA 
intends to publish a Notice of Data Availability and formally request 
submission of data from parties interested in the development of DO 
criteria for other provinces.

    Dated: November 14, 2000.
Geoffrey H. Grubbs,
Director, Office of Science and Technology.
[FR Doc. 00-30542 Filed 11-29-00; 8:45 am]
BILLING CODE 6560-50-U