Chesapeake Bay Dissolved Oxygen Criteria Working Draft No. 1 July 3,2001


CHESAPEAKE BAY DISSOLVED OXYGEN CRITERIA

WORKING DRAFT No. 1	July 3, 2001

NOTE TO REVIEWERS: THIS DOCUMENT PRESENTS THE RESULTS OF WORK TO
DATE BY A TEAM OF BAY REGION SCIENTISTS, STATE AND FEDERAL AGENCY
MANAGERS, AND TECHNICAL PUBLIC STAKEHOLDERS IN DEFINING
CHESAPEAKE BAY SPECIFIC DISSOLVED OXYGEN CRITERIA REFLECTIVE OF THE
PROPOSED REFINED TIDAL WATERS DESIGNATED USES. THE CRITERIA
PRESENTED HERE SHOULD BE VIEWED AS WORKING DRAFTS SUBJECT TO
CHANGE DURING THE PLANNED MULTISTAGE REVIEW PROCESS. WE
ENCOURAGE COMMENTS, IDEAS, RECOMMENDATIONS, AND EXPRESSIONS OF
CONCERN FOCUSED PARTICULARLY ON THE METHODOLOGY APPLIED TO
DERIVE CHESAPEAKE BAY SPECIFIC DISSOLVED OXYGEN CRITERIA.

III. DISSOLVED OXYGEN CRITERIA

Acknowledgments

These Chesapeake Bay specific criteria were derived through the collaborative efforts,
collective knowledge, and applied expertise of the Chesapeake Bay Dissolved Criteria Team:

Rich Batiuk, U.S. EPA Chesapeake Bay Program Office; Denise Breitburg, Academy of Natural
Sciences; Arthur Butt, Virginia Department of Environmental Quality; Tom Cronin, U.S.
Geological Survey; Ifeyinwa Davis, U.S. EPA Region III; Bob Diaz, Virginia Institute of Marine
Science; Rick Hoffman, Virginia Department of Environmental Quality; Steve Jordan, Maryland
Department of Natural Resources; Jim Keating, U.S. EPA Office of Water, Marcia Olson NOAA
Chesapeake Bay Office; Jim Pletl, Hampton Roads Sanitation District; Dave Secor, University of
Maryland Chesapeake Biological Laboratory; GlenThursby, U.S. EPA Office of Research and
Development; and Erik Winchester, U.S. EPA Office of Water.

Scientists from across the country, well recognized for their work in the area of low
dissolved oxygen effects on individual species up to ecosystem trophic dynamics, contributed
their time, expertise, publications, and preliminary data and findings in support of the derivation
of the Chesapeake Bay specific criteria: Steve Brandt, NOAA Great Lakes Environmental
Research Laboratory; Walter Boynton, University of Maryland Chesapeake Biological
Laboratory; Ed Chesney, Louisiana Universities Marine Consortium; Larry Crowder, Duke
University Marine Laboratory; Peter deFur, Virginia Commonwealth University; Ed Houde,
University of Maryland Chesapeake Biological Laboratory; Julie Keister, Oregon State
University; Nancy Marcus, Florida State University; John Miller, North Carolina State
University; Ken Paynter, University of Maryland-College Park; Sherry Poucher, SAIC; Nancy
Rabalias, Louisiana Universities Marine Consortium; Jim Rice, North Carolina State University;
Mike Roman, University of Maryland Horn Point Laboratory; Linda Schaffner, Virginia
Institute of Marine Science; Dave Simpson, Connecticut Department of Environmental

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Protection; and Tim Target, University of Delaware.

Background

Of all life supporting environmental constituents, oxygen is the most essential. In cells,
oxygen serves to store and liberate energy that drives critical vital processes in fishes, crabs and
shellfish such as feeding, growth, swimming, and reproduction. Oxygen constrains patterns of
behavior and production by individuals and population resilience to environmental change and
exploitation. Indeed, several stock assessment models of Chesapeake Bay living resources are
based upon underlying assumptions on how oxygen limits production (von Bertalanffy 1957;
Pauly 1981). Oxygen acts upon living resources as both a lethal agent, when at particularly low
levels; at intermediate levels oxygen limits metabolic rates that might otherwise be higher based
upon other environmental parameters. The Chesapeake Bay harbors a diverse and productive
number of living resources supported by food webs. The challenge of establishing dissolved
oxygen criteria for these living resources and the food webs they depend upon is to characterize
both lethal and limiting effects of oxygen concentration for species that range from copepods to
sturgeon.

Dissolved oxygen in natural waters has two major sources: atmospheric oxygen which
diffuses into the water at the surface, and oxygen which is produced by plants (chiefly free-
floating microscopic plants or phytoplankton) during photosynthesis. Animals, plants and
bacteria consume dissolved oxygen by respiration. Oxygen is also consumed by chemical
processes (e.g., sulfide oxidation, nitrification). Depletion of dissolved oxygen has harmful
effects on animals, as described above, and can also stimulate production of hydrogen sulfide and
ammonia and the release of heavy metals and phosphate from bottom sediments.

The amount of oxygen dissolved in the water changes as a function of temperature,
salinity, atmospheric pressure, and biological and chemical processes. The higher the
temperature and salinity, the lower the equilibrium dissolved oxygen concentration. Gill and
integumentary respiration, the dominant forms of respiration by Chesapeake Bay resource
species, is accomplished by extracting dissolved oxygen across a pressure gradient (rather than
concentration gradient). As the partial pressure of dissolved oxygen increases in the water, the
more readily it can be extracted by an organism. Because partial pressure of dissolved oxygen
increases with temperature and salinity, we would expect that a level of 6 mg/L concentration
will provide a greater supply of oxygen at 30°C (pressure of x percent saturation) than at 20°C (y
percent saturation). This expectation, however, is confounded: poikliothermic ("cold blooded")
organisms will have much higher metabolic rates and oxygen requirements at 30 vs. 2CFC, more
than offsetting the gained availability of oxygen at the higher temperature. The interactions

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between metabolism, temperature, and salinity are complex but must be considered in
establishing Chesapeake Bay dissolved oxygen criteria

Biological processes such as respiration and photosynthesis can affect the concentration
of dissolved oxygen faster than new equilibrium can be reached with the atmosphere. As a
result, for relatively short periods of time, or under sustained conditions of reduced physical
mixing (i.e., stratification of the water column), dissolved oxygen concentration can be driven
well below saturation. The equilibrium (or saturated) concentration of dissolved oxygen in
natural waters ranges from about 6 to 14 milligrams per liter (mg/L). Dissolved oxygen can
decrease to near zero (anoxia), especially in deep or stratified bodies of water or increase as high
as about 20 mg/L (supersaturation) during dense algal blooms.

Oxygen Dynamics

The Chesapeake Bay has a built-in, natural tendency towards reduced dissolved oxygen
conditions, particularly within its deeper waters because of the physical morphology and
estuarine circulation. Its highly productive, shallow waters, coupled its tendency to retain,
recycle, and regenerate the nutrients delivered from the atmosphere and surrounding watershed
set the stage for a nutrient rich environment. The mainstem Chesapeake Bay and its major tidal
rivers with deep channels coming off shallower, broad shoal waters, and the significant influx of
freshwater flows result in stratification of the water column, essentially locking off deeper
bottom waters from mixing with higher oxygenated surface waters. Combined together, the
retention/efficient recycling of nutrients and water column stratification lead to severe reductions
in dissolved oxygen concentrations during the warmer months of the year, generally May to
September.

This depletion generally results from a host of biological and physical factors (e.g.,
Sanford et al. 1990). The annual spring freshet delivers large volumes of freshwater. With the
combination of significant inputs of nutrients with the spring river flows and increasing
temperatures and light, there are large increases in phytoplankton biomass. Phytoplankton not up
taken by filter feeders (e.g.,menhaden, oysters) sink down in the water column into
subpycnocline waters where they are rapidly broken down by bacteria (Malone et al. 1986; Tuttle
et al. 1987; Malone et al. 1988). This loss of oxygen due to bacterial metabolization is
exacerbated by restricted mixing with surficial waters due to the onset of increased stratification
resulting from the spring runoff.

Nearshore, shallow waters in the Chesapeake Bay periodically experience episodes of
low to no dissolved oxygen conditions, in part, resulting from intrusions of bottom water forced
onto the shallow flanks by sustained winds (Carter et al. 1978; Tyler 1984; Seilger et al. 1985;
Malone et al. 1986). In nearshore waters of the mesohaline mainstem Chesapeake Bay,

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Breitburg (1990) documented near bottom dissolved oxygen concentrations characterized by
large diel fluctuations, low daily minima during July and August and the occurrence of daily
minima during dark and morning hours. These nearshore habitats were exposed to episodes of
extreme and rapid fluctuations in dissolved oxygen concentrations (Sanforcl et al. 1990). During
the summer, dissolved oxygen concentrations were observed to drop 6 mg/L in only 4 hours and
more than 1 mg/L in 14 minutes (Breitburg 1990). In depths as shallow as 4 meters, dissolved
oxygen concentrations dropped as low as 0.5 mg/L for up to 10 hours. Diel cycles of low
dissolved oxygen conditions often occur in non-stratified shallow waters where nighttime water
column respiration temporarily depletes dissolved oxygen levels (D'Avanzo and Kremer 1994).

The timing and spatial and volumetric extent of hypoxic and anoxic waters vary from
year to year, largely driven by local weather patterns, timing and magnitude of freshwater river
flow and concurrent delivery of nutrients and sediments into tidal waters, and the corresponding
springtime phytoplankton bloom (Officer et al. 1984; Seliger et al. 1985). In Chesapeake Bay
mainstem, the onset of low to no dissolved oxygen conditions can be as early as April and persist
through September, until fall turnover of the water column. The deeper waters of major tidal
tributaries can exhibit hypoxic and anoxic conditions, with the nature, extent and magnitude of
low dissolved oxygen and the causative factors varying from river to river.

Low Dissolved Oxygen: Historical and Recent Past

From their extensive review of marine bottom water hypoxia and impacts on benthic
communities, Diaz and Rosenberg (1995) stated while hypoxic and anoxic environments have
existed through geological time, their occurrence in shallow coastal and estuarine areas appears
to be increasing, most likely accelerated by human activities. This finding is directly applicable
to Chesapeake Bay. Analysis of the geological history of the Chesapeake Bay, conducted largely
through evaluation of sediment cores, clearly points to periodic hypoxic even anoxic events in
the deep channel mainstem Bay for hundreds to thousands of years back in time (Cooper and
Brush 1991). Prior to the late 17th century, oxygen depleted regions were limited. Over the past
200 years, decadal scale variations in dissolved oxygen conditions in the range of 0.1 - 1 mg/L,
with evidence of even anoxic (<0.1 mg/L) conditions have become more prevalent (Karlsen et al.
2000). The highest spatial and temporal incidence of low to no dissolved oxygen waters were
reached during the 1970s, likely driven by the 2- to 4-fold increase in organic carbon deposition
between the late 1940s to the mid 1970s (Zimmerman and Canuel 1999). Although low to no
oxygen conditions have existed in the Chesapeake across geological time scales, its widespread
occurrence is a much more recent phenomenon.

Against this backdrop of natural, highly variable processes which "encourage" depletion
of dissolved oxygen and historic recordings of low oxygen events over recent geological time
scales, a protective set of dissolved oxygen criteria have been derived, tailored to Chesapeake

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Bay living resources and reflective of the Bay's natural processes.

Approach

[STILL NEED TO ADD SOME INRODUCTORY TEXT LAYING OUT THE OVERALL
APPROACH NESTED WITHIN THE REFINED DESIGNATED USES.]

Building on Chesapeake Bay Science

The scientific underpinning for these Chesapeake Bay specific criteria have been in the
works for decades. The first documentation of seasonal low dissolved oxygen conditions in
Chesapeake Bay was in the 1930s (Newcombe and Home 1938). Basic understanding of
dissolved oxygen dynamics, critical to derivation of criteria reflective of ecosystem process,
began with the research cruises of the Chesapeake Bay Institute from the 1950s through the late
1970s. A 5 year multidisciplinary research program starting in the late 1980s, funded by the
Maryland and Virginia Sea Grant Program, yielded significant advances in understanding of all
facets of oxygen dynamics, effects and ecosystem implications (Smith et al. 1992). These
investigations laid the groundwork for more management focused applications of the science.

Using the Chesapeake Bay Dissolved Oxygen Restoration Goal Framework

Published in 1992, the Chesapeake Bay dissolved oxygen restoration goal was developed
in response to the Chesapeake Executive Council's commitment "to develop and adopt
guidelines for the protection of water quality and habitat conditions necessary to support the
living resources found in the Chesapeake Bay system and to use these guidelines" (Chesapeake
Executive Council 1987). The dissolved oxygen restoration goal consisted of a narrative
statement supported by specific target dissolved oxygen concentrations applied over specified
averaging periods and locations (Table III-l) (Jordan et al. 1992). Dissolved oxygen effects
information was compiled for 14 identified target species1 of fish, molluscs, and crustaceans as
well as for other supporting benthic and planktonic species within the Bay food web. The target
concentrations and their specified temporal averaging and spatial application were determined
from analysis of dissolved oxygen levels that would provide the levels of protection described
within the narrative restoration goal. Best professional judgement was used in areas where there
were gaps in the information base on dissolved oxygen effects available a decade ago.

The original dissolved oxygen restoration goal and its supporting framework made three
breakthroughs at that time of significance to supporting derivation and management application

1 These target species were from a larger list of commercially, recreationally and
ecologically important species reported in Habitat Requirements for Chesapeake Bay Living
Resources-Second Edition (Funderburk et al. 1991).

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of the Chesapeake Bay specific dissolved oxygen criteria within this document. The dissolved
oxygen target concentrations varied with vertical depth through the water column as well as
horizontally across the expanse of the Bay and its tidal tributaries, directly reflecting variations
required levels of protection for different living resource habitats. Second, the averaging periods
for each target concentration was tailored to specific habitats, with a recognition of short term
exposures to concentrations belong the target concentrations were allowable and still protective
of living resources. Finally, the dissolved oxygen goal document contained a methodology
through which water quality monitoring data and model simulated outputs collected over varying
frequencies could be directly assessed in terms of the percentage of time that areas of bottom
habitat or volumes of water column habitat were predicted to meet or exceed the applicable target
dissolved oxygen concentrations.

Regionalizing the EPA Virginian Province Saltwater Dissolved Oxygen Criteria

With the publication of the EPA Ambient Water Quality Criteria for Dissolved Oxygen
(Saltwater): Cape Cod to CapeHatteras came a decade's worth of systematically developed
dissolved oxygen effect data along with synthesis and close evaluation of several decades of
effects data published in the scientific peer reviewed literature (Thursby et al. 2000). The
approach to derive these dissolved oxygen criteria combined features of the traditional water
quality criteria with anew biological framework. A mathematical model was used to integrate
time (replacing the concept of an averaging period) and establish protection limits for different
life stages (i.e., larvae verus 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 EPA Guidelines) (Stephan el al. 1985).

The EPA Virginian Province dissolved oxygen saltwater criteria (hereafter referred to as
the Virginian Province Saltwater Criteria) addressed three areas of protection: 1) protection for
juvenile and adult survival, 2) protection for growth effects, and 3) protection for larval
recruitment effects. In doing so, the criteria document segregated effects on juveniles and adults
from those on larvae. The survival data on the sensitivity of the juveniles and adults were
handled in a traditional EPA guidelines manner. To address cumulative effects of low dissolved
oxygen on larval recruitment to the juvenile life stage (i.e., larval survival as a function of time) a
new biological approach was taken. These criteria were derived using a mathematical model that
evaluates the effect of dissolved oxygen conditions on larvae by tracking the intensity and
duration of low dissolved oxygen effects across the larval recruitaent season. Protection of
larvae of all species is provided by using low dissolved oxygen effects data on larval stages of
nine sensitive estuarine/coastal organisms.

The Virginian Province saltwater juvenile/adult survival and growth criteria provide

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boundaries within which to judge the dissolved oxygen status of a given site. If the dissolved
oxygen concentrations are above the chronic growth criterion (4.8 mg/L), then this site would
meet objectives for protection. If the dissolved oxygen conditions are below the juvenile/adult
survival criterion (2.3 mg/L), the site would not meet objectives for protection. When the
dissolved oxygen conditions are between these two values, then the site would require evaluation
using the larval recruitment model that integrates duration and intensity of the low dissolved
oxygen conditions to determine suitability of habitat for the larval recruitment protection
objective.

The Virginian Province saltwater dissolved oxygen criteria document and its underlying
effects database and methodologies were structured to support regional specific derivation of
dissolved oxygen criteria Using the available effects data and outlined methodologies, criteria
can be tailored to the species, habitats, and nature of dissolved oxygen exposure regimes of
different estuarine, coastal, and marine waters. The segregation by life stages allows the criteria
to be factored into the refined tidal water designated uses, which themselves, in part, reflect use
of different habitats by different life stages. This segregation by life stage is a significant
difference from traditional aquatic life criteria.

However, the Virginian Province saltwater criteria were not explicitly set up to address
natural vertical variations in dissolved oxygen concentration. If Chesapeake Bay specific criteria
were derived through a strict application of the EPA saltwater criteria methodology, there would
not be the flexibility needed to tailor each set of criteria to the refined tidal water designated uses
presented in Appendix A. The resultant Bay criteria would be driven solely by larval effects data
irrespective of depth and season.

As described throughout the rest of this document, the Chesapeake Bay specific criteria
were derived through the regional application of the Virginian Province effects data base and
application of traditional toxicological and new biological-based criteria derivation
methodologies. Chesapeake Bay specific science was factored directly into each step of the
criteria derivation process. The extensive Virginian Province dissolved oxygen effects database
was first focused down on only Chesapeake Bay species and then supplemented with additional
Chesapeake Bay species effects data from the scientific literature. The Virginian Province larval
recruitment model was modified to better reflect Chesapeake Bay conditions, with its application
broadened to include additional Chesapeake Bay species. Finally, specific steps were taken to
factor the requirement to provide protection of species listed as threatened/endangeredin
Chesapeake Bay into the Bay specific criteria.

With the full support of and technical assistance from the U.S. EPA Office of Research
and Development's Atlantic Ecology Division and the U.S. EPA Office of Water's Office of

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Science and Technology, the data and methods from the Virginian Province saltwater dissolved
oxygen criteria document were applied to the derivation of Chesapeake Bay specific dissolved
oxygen criteria described within this document.

Chesapeake Bay Species Only

Only species documented as commonly inhabiting tidal waters within the Chesapeake
Bay or its tidal tributaries and embayments were used in the derivation of these Bay specific
dissolved oxygen criteria. This decision was made in adherence to the EPA Guidelines which
allows and encourages regional and site specific criteria derivation. There were a total of 36
individual species of fish, crustaceans and molluscan shellfish within the Virginian Province
saltwater criteria effects data base. Only four species were dropped from the dissolved oxygen
effects database used in deriving the Chesapeake Bay criteria (Table II-2). The green crab
(Caricinus maenas) and the mysid Americamysis bahia are not found in Chesapeake Bay (U.S.
Environmental Protection Agency 1998). American lobster (Homarus americanus) and Atlantic
surfclam (Spisula solidissima) have both been observed in the Chesapeake Bay, but only near the
Bay mouth in very high salinities. American lobster larvae require relatively low temperatures
(20°C) and high salinities (30 ppt) for successful development. These conditions do not normally
occur in the Bay, explaining why lobster larvae and adults are rarely found in Bayfield
collections. Likewise, Atlantic surfclams require high salinity conditions infrequently found in
Chesapeake Bay other than right at the Bay mouth/Atlantic Ocean interface where low dissolved
oxygen conditions are not observed. For these reasons, these four species were dropped from the
Chesapeake Bay specific effects database.

Bay Specific Juvenile/Adult Survival Criteria

The criterion minimum concentration or CMC, providing a lower limit for continuous
exposures protecting juvenile and adult survival, was recalculated using the Chesapeake Bay
specific effects database of 32 diverse species of fish, crustaceans, and molluscs. Dropping the
four species from the original Virginian Province dissolved oxygen saltwater criteria effects data
base changed the total number of genera represented from 22 to 18. The new Bay specific acute
criteria value was recalculated to be 1.66 mg/L, compared to the Virginian Province criterion
value of 1.64 mg/L. Then applying the new mean LC5/LC50 ratio of 1.35 (compared to a ratio
of 1.38 for the Virginian Province criterion), the recalculated Bay specific juvenile/adult survival
CMC value is 2.24 mg/L. By dropping non-Chesapeake Bay species, the concentration
protective of juvenile and adult survival specific to Chesapeake Bay changed by only 0.03 mg/L
from the Virginian Province saltwater criterion value of 2.27 mg/L (U.S. Environmental
Protection Agency 2000).

Bay Specific Larval/Juvenile Growth Criteria

The criterion value protective against adverse impacts on growth under continuous

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exposures, termed the criterion continuous concentration or CCC, recalculated for Chesapeake
Bay species only changed only 0.2 mg/L from 4.8 mg/L to a Chesapeake Bay specific value of
5.0 mg/L. The CCC value was recalculated by dropping the mysid and lobster growth effects
data from the data base listed in Table 2, page 10 of the Virginian Province saltwater criteria
document (U.S. Environmental Protection Agency 2000) and using a new n or number of species
of 18 instead of 22.

Larval Recruitment Model Application

In the derivation of Chesapeake Bay specific criteria, the Virginian Province saltwater
criteria larval recruitment model was used as confirmation that the values selected for the
migratory spawning/nursery and shallow/open criteria were fully protective of larval recruitment.
In the case of the deep water criteria, given the focus on protection of species inhabiting the
pycnocline region and use of bay anchovy as an ecologically important, representative species,
the application of the larval recruitment model was central in derivation of the deep water criteria
values. See the Recognized Strengths and Limitations section below for a more complete
discussion of the larval recruitment model.

A series of modifications were made to the original Virginian Province saltwater
criteria's larval recruitment model parameters for length of recruitment season and duration of
larval development. These Virginian Province-wide (Cape Cod to Cape Hatteras) model
parameter values were revised, as described below, to better reflect more Chesapeake Bay
specific conditions (Table III-3).

Length of Recruitment Season

The literature supports a larval release season of 120 days or more for Cancer,
Dyspanopeus, Eurypanopeus, and Libinia based on the presence of gravid females and larvae in
field collections (Anger et al. 1981a; Anger et al. 1981b; Broad 1957; Chamberlain 1957;
Costlow 1961; Johns 1981; Logan and Epifanio 1978; Maris 1986; Ryan 1956; Sandifer 1973;
Sandifer and Van Engel 1971; Sasaki et al. 1986; Sastry 1970; Sastry 1977; Sastry and McCarthy
1973; Sulkin and Norman 1976; Wass 1972; Williams 1984). Homarus larvae and adults are
rarely found in the Bay, therefore collection data is not available. Palaemonetes have an
extremely wide reproductive season that extends even longer than the brachyurans. The
Virginian Province saltwater criteria document infers that the actual period over which most of
these crustaceans release larvae is only 30-40 days (except for Palaemonetes). This was not
supported by the literature for Chesapeake Bay. However, given interest "to capture the period
of predominant recruitment, rather than observance of the first and last dates for zoeal presence
in the water column" (U.S. Environmental Protection Agency 2000), one could conservatively
state that brachyuran larvae are released over a 75 day period in Chesapeake Bay. Palaemonetes
larvae are released over a period of at least 100 days due to its greater reproductive flexibility.

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These values, added to the length of larval development period, provided the following
Chesapeake Bay specific values for length of recruitment season: Cancer-100 days;
Dyspanopeus-90 days; Eurypanopeus-90 days; Libinia-ttQ; and PalaemonetesA 20 days (Table
III-3).

In Chesapeake Bay, striped bass spawn over a 30-40 day period. By adding in the larval
stage duration of28 days, a conservative estimate for the recruitment season is around 70 days
(Grant and Olney 1991; McGovern and Olney 1996; Olney et al. 1991; Rutherford and Houde
1995; Secor and Houde 1995; Ulanowicz and Polgar 1980).

Silversides along with other east-coast estuarine dependent species tend to show
latitudinal clines in the date of initiation of spawning and spawning duration (e.g., southern sites
have longer durations). Silversides are serial batch spawners that spawn over a less than 2 month
period in northern regions of the east coast, 2-3 months around New York, and 3-4 months in the
Maryland portion of Chesapeake Bay(Conover and Present 1990; Conover 1992; Gleason and
Bengston 1996). A 140 day recruitment season factors in a 90 day spawning period with a 50
day larval stage duration.

Red drum are also serial batch spawners. Documentation for red drum spawning season
is mostly for southern systems and varies between 2 months (Wilson et al. 1994, Rooker and
Holt 1997) and 3 months (McMichael and Peters 1987). A 140 day recruitment season factors in
a 90 day spawning period with a 50 day larval stage duration.

Duration of Larval Development

The Virginian Province saltwater criteria document states that the larval model for
crustaceans includes all larval stages and the transition from larval to megalopal (post-larval)
stage, but not the megalopal stage in its entirety. The model assumes that once a zoeal larva has
made the development transition to megalopa, then there is no further low dissolved oxygen
effect (the model only applies the late larval to megalopa dose-response curve for one 24 hr time
period) (U.S. Environmental Protection Agency 2000). Therefore, the duration used in the model
should be based on the duration of larval development plus one day for molting to the megalopal
stage. These more Chesapeake Bay specific estimates of the duration of larval development are
rounded up to the nearest whole day-Cancer-22 days; Dyspanopeus-17 days; Eurypanopeus-\l
days (assumed the same as D. sayi as in the Virginian Province saltwater criteria document);
Homarus-15 days; Libinia-6 days; and Palaemonetes-15 days-are supported by a wide array of
literature (Anger et al. 1981a; Anger et al. 1981b; Broad 1957; Chamberlain 1957; Costlow
1961; Johns 1981; Logan and Epifanio 1978; Maris 1986; Ryan 1956; Sandifer 1973; Sandifer
and Van Engel 1971; Sasaki et al. 1986; Sastry 1970; Sastry 1977; Sastry and McCarthy 1973;
Sulkin and Norman 1976; Wass 1972; Williams 1984).

10

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Impairment Percentage

Many populations of estuarine/coastal organisms maybe more impacted by mortality
occurring during the juvenile and adult stages than during the larval stage(s). In this regard, a
particular individual larva is not as important to the population as a particular individual juvenile
or adult. Therefore, populations can tolerate different levels of impact at different stages of
individual development (U.S. Environmental Protection Agency 2000). Protection against a
greater than 5 percent cumulative reduction in larval seasonal recruitment was applied within the
Chesapeake Bay specific application of the larval recruitment effects models, consistent with the
Virginian Province saltwater criteria.

Larval 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 Chesapeake
Bay species, corresponds to times of the year when low dissolved oxygen conditions occur. The
selection of a 5 percent attrition rate does not mean that a population can not withstand a greater
percentage effect with no significant effect on recruitment. Rather, the 5 percent means that this
level of effect should be insignificant relative to recruitment in the absence of low dissolved
oxygen conditions. In other words, there should be no difference in recruitment between the zero
and 5 percent rates of attrition due to exposure to low dissolved oxygen.

EPA recognizes that large losses of larval life stages occur naturally. Some species may
be able to withstand a greater than 5 percent loss of larvae from exposure to low dissolved
oxygen or other causes without an appreciable effect on juvenile recruitment. However, this may
not be the case for certain highly sensitive species or populations that are already highly stressed,
for example 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 the 5 percent loss in larval recruitment from exposure to low dissolved
oxygen may not be protective enough.

The 5 percent level is consistent with the approach outlined in the EPA Guidelines for
deriving ambient aquatic life water quality criteria because 5 percent impairment is also the level
of protection afforded to juvenile and adult life stages (Stephan et al. 1985). In the absence of
data showing how much attrition may be caused by low dissolved oxygen conditions alone and
still have a minimal effect on natural larval recruitment to the juvenile stage, a conservative level
of acceptable impairment has been applied. This level of reduced larval recruitment from
exposure to low dissolved oxygen along is believed to be protective for most species. The goal
is to provide a level of protection from exposure to low dissolved oxygen that will not cause
significant loss to juvenile recruitment class above that expected to occur naturally.

Application of the EPA Freshwater Dissolved Oxygen Criteria

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The Virginian Province saltwater criteria, developed for application to the east coast
region stretching from Cape Cod to Cape Hatteras, was largely derived from laboratory-based
effects data using test conditions with salinities ranging from oligohaline (5 ppt) to full ocean
salinities (35 ppt). Although a majority of the tests were run at salinities greater than 15 parts per
thousands (ppt), data from the literature included a number of tests whose estuarine species were
exposed to salinities down around 5 ppt. Many of the test organisms were estuarine species with
wide ranging salinity tolerances, but the location of the EPA laboratory largely dictated the need
to run the tests at higher salinities given the source water being the lower reaches of Narragansett
Bay. With extensive tidal fresh (0-0.5 ppt) and oligohaline (>0.5-5ppt) habitats in the upper
Chesapeake Bay and upper reaches of most tidal tributaries, criteria established for these less
saline habitats must be protective of the resident species that inhabit them. To bridge this effects
information gap, the applicable EPA freshwater dissolved oxygen criteria were applied to ensure
the Chesapeake Bay specific criteria were fully protective of freshwater species inhabiting tidal
waters (U.S. Environmental Protection Agency 1986).

The EPA freshwater criteria document stipulated five limits for dissolved oxygen effects
on warmwater species (Table III-4). For protection of early life stages, these include a seven day
mean of 6.0 mg/L and a 5.0 mg/L instantaneous minimum. A 30 mean of 5.5 mg/L, a 7 day
mean of 4.0 mg/L, and a instantaneous minimum of 3.0 mg/L provide protection of other life
stages. These freshwater criteria represent limits that are generally higher (more restrictive) than
the Virginian Province saltwater criteria, and are higher than any effect levels reported for
survival of juveniles, other than sturgeon, in salt waters. Some of the most sensitive survival and
growth responses reported for warmwater species in the freshwater criteria document were for
the early life stages of channel catfish (Ictalurus punctatus) and largemouth bass (Micropterus
salmoides), both of which are present in tidal fresh habitats throughout Chesapeake Bay.

Early Life Stages

The EPA freshwater criteria for protection of early life stage warmwater species were
based on embryonic and larval life stage effects data for the following eight species: laigemouth
bass*, black crappie*, white sucker, white bass*, northern pike, channel catfish*, walleye, and
smallmouth bass* (U.S. Environmental Protection Agency 1986). Given the five asterisked (*)
species are species resident in Bay tidal fresh waters, the freshwater early life stage criteria are
fully applicable to Chesapeake Bay tidal fresh habitats.2

2 Please see Figure 1 on page 14 and the text on pages 17-18 in the EPA freshwater
dissolved oxygen criteria document for more details (U.S. Environmental Protection Agency
1986).

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Other Life Stages

The freshwater criteria protective of other life stages were derived from a much wider
array of fish and invertebrate species, many of which are documented to occur in Chesapeake
Bay tidal fresh habitats (U.S. Environmental Protection Agency 1986; 1998). These freshwater
criteria protective of other life stages are fully applicable to Chesapeake Bay habitats with
salinities of less than 0.5 ppt.

Species Listed as Endangered/Threatened

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 is appropriate
to consider deriving site-specific dissolved oxygen criteria (U.S. Environmental Protection
Agency 2000). Based on an in-depth review of all federal agency (U.S. Fish and Wildlife
Service, National Oceanic and Atmospheric Administration) and states with Bay tidal waters
(Maryland, Virginia, District of Columbia, and Delaware) lists of threatened/endangered species,
only the two endemic sturgeon species were found to be the only listed species inhabiting
Chesapeake Bay and tributary tidal waters that would be directly impacted by low dissolved
oxygen conditions (Appendix B, Tables B-l and B-2).

Shortnose sturgeon (Acipenser brevirostrum) have been federally protected since 1967
(National Marine Fisheries Service 1998) and may now longer reproduce in Chesapeake Bay
waters. Shortnose sturgeon have been documented to visit the Chesapeake from the Delaware
Bay through the C&D Canal (based upon genetic evidence, J. Waldman, Hudson River
Foundation, NY, pers. comm.).

Atlantic sturgeon (Acipenser oxyinchus) have been listed by Virginia as endangered since
1974, and Maryland instituted a ban on harvests in 1990 [EDITOR'S NOTE: NEED TO
CONFIRM THIS DATE WITH MD DNR FISHERIES]. There is consensus that Atlantic
sturgeon now longer reproduce in Maryland waters, but there is recent evidence of spawning in
Virginia Iributaries, suggesting that a relic population may still reside there (J. Musick, VIMS,
pers. comm). Due to the threatened status of Atlantic sturgeon throughout their U.S. range, a
moratorium on all Atlantic sturgeon harvests was adopted in 1997 by the Atlantic States Marine
Fisheries Commission (Colligan et al. 1998). A recent petition to list Atlantic sturgeon on the
federal register of Endangered Species was not accepted, in part, because Atlantic States Marine
Fisheries Commission's current management, including a 40-yr moratorium on harvests, was
deemed sufficient to restore depleted Atlantic sturgeon stocks [EDITOR'S NOTE: NEED TO
GET THE FEDERAL REGISTER CITATION FOR THIS DECISION]. Thus for the purposes
of this report, both Atlantic sturgeon and shortnose sturgeons in the Chesapeake Bay are
attributed a threatened/endangered status.

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Sturgeons in the Chesapeake Bay and elsewhere are unusually sensitive to low dissolved
oxygen conditions. In comparison with other fishes, sturgeon have a limited behavioral and
physiological capacity to respond to hypoxia (references reviewed and cited by Secor and
Niklitschek 2001). Sturgeon basal metabolism, growth, consumption, and survival are all very
sensitive to changes in oxygen levels, which may indicate a relatively poor ability by sturgeons
to oxyregulate. During the summertime, temperatures >20°C amplify the effect of hypoxia on
sturgeons and other fishes due to a temperature-oxygen "squeeze" (Coutant 1987). In bottom
waters, this interaction results in substantial reduction of habitat.

Few studies have addressed lethal effects ofhypoxia on sturgeons. Jenkins et al. (1994)
observed 86-100 percent mortality for 25-64 day old fish in an acute 6 hour exposure to 2.5 mg/L
at 22.5°C (30 percent saturation). Older juveniles (100-301 days old) experienced 12-20 percent
mortality under the same conditions. Short term exposure to 3.0 mg/L (35 percent saturation)
resulted in 18-38 percent mortality for juveniles ranging from 20-77 days in age. No mortality
was observed for exposures to > 3.5 mg/L (42 percent saturation). Long term exposure (10 days)
of Atlantic sturgeon young-of-the-year juveniles (150-200 days old) to 2.8-3.3 mg/L at 26°C (37-
44 percent saturation) resulted in complete mortality over a ten day period in three of four
replicates (Secor and Gunderson 1998). The fourth replicate experienced 50 percent mortality.
At 20°C and 2.3-3.2 mg/L (27-37 percent saturation), 12-25 percent mortality was observed.
Bioenergtic and behavioral responses indicate that young of the year juveniles (-30 to 200 days
old) will experience lost production in those habitats with less than 60 percent saturation
(Niklitschek 2001).

Based on analysis of published effects data for Atlantic and shortnose sturgeon (Secor
and Gunderson 1998), a 96 hour LC50 value of 2.89 mg/L was estimated.3 Multiplying this
value by the LC5/LC50 ratio of 1.35 generates a sturgeon species specific criterion minimum
concentration or CMC value of 3.9 mg/L protective of survival. To be consistent with the EPA
Guidelines, this same 96 hour LC50 value was used with the Chesapeake Bay specific effects
data base to recalculate the CMC. The resulting final acute value was 2.6 mg/L yielding a
recalculated Bay specific CMC value of 3.5 mg/L, protective of sturgeon survival at
temperatures up to 26°C. These effects data and the resultant criterion value should be applied
with the understanding of the possibility for a temperature-dissolved oxygen interaction.

To determine whether a Bay criterion value would also be protective of growth of

3 The shortnose sturgeon effects data published by Jenkins et al. 1993 could not be used
in the recalculation of the CMC value and still adhere to EPA Guidelines given the test
organisms were only exposed for 6 hours.

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sturgeon, a sturgeon bioenergetics model developed by Niklitschek and Secor (2000) was
applied. From data from Figure 2 in Niklitschek and Secor (2000), the dissolved oxygen
saturation concentration at 20°C and 8 ppt salinity is 8.67 mg/L. Applying the Bay species
derived criterion protective of growth of 5.0 mg/L (which equates to 58 percent saturation at
20°C), Figure 2 suggests that growth effects are likely to be insignificant at the 58 percent
saturation level. The Bay specific criterion protective against adverse growth impacts at
continuous concentration would be protective of impacts on sturgeon growth as well.

Atlantic sturgeons are known to occur at depths between 1 meter to greater than 25
meters; shortnose sturgeons have been observed between 1 and 12 meters (Kieffer and Kynard
1997); Savoy and Shake 2000: Welsh et al. 2000). In the Chesapeake Bay during the winter,
Atlantic sturgeon selected deeper habitats occurring in the deep channel (Secor et al. 2000;

Welsh et al. 2000). Sturgeon have very wide tolerances of salinity. During their first year of
life, shortnose sturgeon tend to occur in freshwater (Dovel et al. 1992; Haley 1999) but can
tolerate salinities up to 15 ppt (Jenkins et al. 1995; Niklitchek 2001). Laboratory experiments
also showed that young-of-the-year Atlantic sturgeon tend to experience higher survivorship at
salinities 15 ppt, but lethal responses were not as severe at higher salinities as those observed
for shortnose sturgeon (Niklitschek 2001). One year old shortnose sturgeon can tolerate salinities
up to 20 ppt (Jenkins et al. 1995), and 1-year old Atlantic sturgeon are capable of invading
coastal marine waters (Secor et al. 2000). Based upon distributional evidence, older juvenile and
adult shortnose sturgeon are limited to oligohaline and mesohaline regions of estuaries (<19 ppt),
while by their second year of life, Atlantic sturgeon are fully tolerant of salinities ranging 0-35
ppt (Dovel and Berggren 1983; Dovel et al. 1992, Kieffer and Kynard 1993; Colligan et al.
1998; Secor et al. 2000). Thus, Atlantic sturgeon are not limited by bathymetry and salinity
within the Bay and would be expected to utilize all tidal waters, including sub-phycnocline
waters, contingent upon suitable water quality. Shortnose sturgeon habitats would overlap those
of Atlantic sturgeon for salinities <19 ppt.

Scientific Literature Findings

For each tidal water designated use-based set of Bay dissolved oxygen criteria, a review
of the relevant scientific literature beyond those data already referenced within the Virginian
Province criteria document was conducted to both draw in more recent published findings as well
as more Chesapeake Bay specific data. These scientific literature findings were principally used
to confirm the derived criteria values. In the case of the deep channel designated use, the
scientific literature formed the basis for the seasonal-based criterion value.

Instantaneous vs. Daily Averaged Minima

Where the underlying time to effect data were supportive, an instantaneous minimum
value was selected over a one day averaged minimum value. In practical terms, sites are

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generally only going to be monitored once per day and an instantaneous minimum and daily
averaged minimum would be the same. However, there may be cases where continuous
monitoring is done. At such sites a 24 hour average could include a significant stretch of time
when dissolved oxygen concentrations were well below the allowable one day value. This is
critical if dissolved oxygen concentrations were near or below lethal thresholds; likely less
important for concentrations just below values for the protection against impacts on growth.

Recognized Strengths and Limitations

As with any science-based set of criteria, these Chesapeake Bay specific dissolved
oxygen criteria have recognized strengths in the derivation approach taken as well as limitations.
EPA believes the dissolved oxygen criteria provided in this document are sufficiently protective
under most Chesapeake Bay conditions where aquatic organism are not otherwise unduly
stressed.

Salinity Effects

The Virginian Province saltwater dissolved oxygen effects database generated at the EPA
Office of Research and Development Atlantic Ecology Division Laboratory in Narragansett,
Rhode Island is geared towards >15 ppt salinities. There were a subset of tests run at much
lower salinities (e.g., striped bass larvae). Low dissolved oxygen effects synthesized from the
published literature used in derivation of the EPA criteria included tests run at salinities lower
than 15 ppt salinity (e.g., Burton et al. 1980 research on menhaden, spot). All these tests were
run at salinities found to be non-stressful to the respective test organisms. From results of the
EPA generated data sets and published scientific peer reviewed literature reporting effects of
exposure to low dissolved oxygen under varying salinities and the similarity of the EPA
freshwater and saltwater dissolved oxygen criteria, salinity does not appear to have an influence
on sensitivity to low dissolved oxygen at non-stressful salinities.

Temperature Effects

The criteria do not explicitly address the potential interactions of high temperatures and
effects of low dissolved oxygen. High temperatures and low dissolved oxygen often appear
together. Generally, low dissolved oxygen would be more lethal at water temperatures
approaching the upper thermal limit for species. High temperatures can exacerbate effects of
exposure to low dissolved oxygen in at least two ways. Surface or shoal regions of high
temperature will cause fish to seek out cooler habitats, yet these deeper habitats are more likely to
contain hypoxic waters. This "habitat squeeze" (Coutant 1985) curtails summertime habitats
and production (Brandt and Kirsch 1983; Secor and Niklitschek 2001). A number of species
have shown heightened sensitivity to low dissolved oxygen concentrations at higher, but still
non-lethal temperatures (Breitburg et al. 2001). There does not exist sufficient data to fully
quantify and, therefore, build temperature/dissolved oxygen interactions into a set of Chesapeake

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Bay specific dissolved oxygen criteria.

An additional concern is if the same species from different geographic regions might
react differently to low dissolved oxygen, with populations from traditionally warmer waters less
sensitive because of adaptation to lower concentrations of oxygen associated with the warmer
temperatures. Alternately, higher temperatures may cause warmer water populations to need
more dissolved oxygen and thereby make them more sensitive to lower concentrations. To see
whether such geographic differences exist, northern (Rhode Island) and southern populations
(Georgia or Florida) of two invertebrates (the mud crab, Dyspanopeus sayi, and the grass shrimp,
Palaemonetes vulgaris) and one fish (the inland silverside, Menidia beryllina) were tested in the
laboratory at non-stressful temperatures. Exposure-response relationships were similar for
northern and southern populations of each species, supporting the use of data from one region to
help develop safe dissolved oxygen limits for other regions (Coiro et al. submitted). This is
particularly useful for the Chesapeake Bay. Even though the Bay is covered in the geographic
region of the Virginian Province criteria document, many of the tested species in that document
are with populations from the northern portion of the Virginian Province.

Behavioral Effects

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. Concentration associated with avoidance are very similar to those
observed to result in adverse effects on growth

[EDITOR'S NOTE: STILL NEED REFERENCES CITED HERE SUPPORTING THESE
STATEMENTS. THE CRITERIA TEAM IS IN THE PROCESS OF DRAFTING UP TEXT
LAYING OUT CONCERNS FOR NOT ADDRESSING BEHAVIORAL EFFECTS WITHIN
THE CRITERIA, WITH APPROPRIATE CITATIONS.]

Larval Recruitment Model

General Limitations

There still exists uncertainties with the percent of the population exposed to low
dissolved oxygen, length of the actual spawn, and protection of spawning events concentrated
over short time frames. The sensitivity of life stages that do not vertically migrate and do not
experience cyclic exposures to low oxygen conditions should not be used to represent life stages
that do vertically migrate and may benefit from periods of low oxygen stress in more shallow
waters. The assumption implicit in the model is that all spawning days are equal. Due to
meteorological, food web, and other influences spawned eggs among dates of production are not
expected to equally contribute to successful survival to juvenile and adult stages. Nor are eggs

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produced continuously throughout the spawning season. In particular, species show spawning
behaviors and early survival rates that are dependent upon lunar tidal patterns, weather-driven
changes to water quality (e.g. winds and temperature changes), and available forage for young.
Indeed, it has been well documented for slriped bass that most survival can come from a
relatively narrow period of time within the entire spawning period (Ulanowicz and Polgar 1980;
Secor and Houde 1995; Secor 2000). Unfortunately, this window of spawn dates that
corresponds to later high survivorship can not be predicted. Therefore, conservative assumptions
on production of young must be made to insure hypoxia has minimal effects on offspring that
might result from all portions of the spawning season. The model is not conservative in that it
assumes that 30 days, for example, of reduced larval growth does not translate into dissolved
oxygen related mortality. There are a number of reports of the consequences of slow growth in
terms of increased prcdation mortality.

Continuous versus cyclic exposure

The larval recruitment model was applied with Chesapeake Bay specific species and data
in support of the Bay criteria. One of 1he challenges of developing such a model is extrapolating
laboratory exposure to that in the Bay. Most lab tests use an exposure that is continuous at
specific concentrations. However instead exposure often times, for the species and life stages
tested, is cyclic due to tidal flux as well as horizontal and vertical transport. The model outputs
used in supporting the Bay criteria were based on an assumption of continuous exposure, which
may overestimate the dissolved oxygen concentrations required to protect against significant
impacts on larval recruitment. Several of the species and larval stages used to develop the Bay
criteria have been documented to vertically migrate, which results in cyclic exposure. The
Virginian Province saltwater criteria document clearly illustrates that assumptions of continuous
exposure overestimate impact when exposure is naturally cyclic (Figure 11 on page 22 in U.S.
Environmental Protection Agency 2000). Use of response data generated from continuous
exposures may be inappropriate if the species/life stage in question vertically migrates or is
regularly exposed to a range of dissolved oxygen concentrations with horizontal transport. The
use of responses based on continuous exposures rather than cyclic exposures may overestimate
the level of impairment.

Chesapeake Bay Dissolved Oxygen Criteria Derivation

Chesapeake Bay dissolved oxygen criteria were established to provide protection for the
estuarine living resources inhabiting five principal habitat categories: migratory spawning and
nursery habitats, shallow water habitats, open water habitats, deep water habitats, and deep
channel habitats. These five categories are drawn from the refined designated uses for the
Chesapeake Bay and its tributaries tidal waters (Figure III-l). See appendix A for a more

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detailed description of the refined designated uses and the approach taken in developing and
delineating them.

Migratory Spawning and Nursery Designated Use Criteria

Criteria supportive of the migratory spawning and nursery designated use must fully
protect the "propagation and growth of balanced indigenous populations of ecologically,
recreationally, and commercially important anadromous and semi-anadromous fish species
inhabiting spawning and nursery grounds from mid-February to early June." This means
protecting the survival and growth of all life stages-eggs, larvae, juveniles, and adults—for a set
number of target species and their underlying food sources. As described below, the migratory
spawning and nursery designated use criteria are based on establishing dissolved oxygen
concentration protective against losses in larval recruitment, growth effects on larvae and
juveniles, effects on the early life stages of resident tidal fresh species, and effects on
threatened/endangered species.

Criteria Components

Protection Against Larval Recruitment Effects

Application of the Virginian Province saltwater criteria larval recruitment effects model
generates a relationship illustrated as a curve, projecting the cumulative loss of recruitment
caused by exposure to low dissolved oxygen. The number of acceptable days of seasonal
exposure to low dissolved oxygen decreases as the severity of the low oxygen conditions
increase. The migratory spawning and nursery criteria must ensure protection of larvae as they
recruit into the juvenile/adult population.

The Virginian Province saltwater criteria larval recruitment curve levels out at
approximately 4.6 mg/L beyond 30-40 days exposure (Figure III-2). Dropping the non-
Chesapeake Bay resident species and then applying a series of Chesapeake Bay specific
modifications to the larval recruitment model parameters, as described previously, yields a curve
which closely follows the original Virginian Province saltwater criteria curve, but which levels
off around 4.7 mg/L. Dissolved oxygen concentrations/exposure durations falling the above the
curve would be protective against larval recruitment effects.

Protection Against Growth Effects

To ensure recruitment to the adult population, the Bay criteria must ensure protection
against growth effects on rapidly developing larvae and juvenile. The Virginian Province
saltwater criteria document recommends 4.8 mg/L as the threshold above which long-term,
continuous exposures should not cause unacceptable growth effects (U.S. Environmental
Protection Agency 2000).

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This chronic criterion value was derived from laboratory evaluations of the effects of low
dissolved oxygen on growth, principally with larval and early juvenile life stages. Growth effects
on these early life stages were used as the basis of the chronic criterion because: 1) growth is
generally the more sensitive endpoint measure upon exposure to low dissolved oxygen compared
with survival; 2) results for other sublethal endpoints like reproduction were very limited; 3)
limited data available indicated that thresholds protecting against growth effects are likely to be
protective against reproductive effects; and 4) larval and juvenile life stages were more sensitive
to effects from low dissolved oxygen then were adults (U.S. Environmental Protection Agency
2000).

As described previously, when the non-Chesapeake Bay species are removed from the
Virginian Province saltwater criteria dissolved oxygen growth effects data base, the recalculated
Bay specific criterion protective against growth effects is 5.0 mg/L.

Protection for Early Life Stages for Resident Tidal Fresh Species

The EPA freshwater dissolved oxygen criteria sets a 7 day mean of 6.0 mg/L and 1 day
instantaneous minimum of 5.0 mg/L for the protection of early life stage warmwater freshwater
species (U.S. Environmental Protection Agency 1986).

Protection Against Effects on Threatened/Endangered Listed Species

As illustrated previously, short term exposures to dissolved oxygen concentrations of
>3.5 mg/L and longer term exposures to > 5mg/L would provide protection for survival and
growth of Atlantic and shortnose sturgeon (Secor and Niklitschek 2001).

Scientific Literature

Laboratory results from work by Brandt et al. (XXXX) indicate that striped bass food
consumption and growth decline as oxygen levels decline. Continuous exposure to dissolved
oxygen concentrations of 4 mg/L or less caused slriped bass to lose weight even through food
was always unlimited. Previous experiments on the effects of oxygen levels on striped bass have
also shown that dissolved oxygen concentrations of less than 3-4 mg/L adversely affects feeding
(Chittenden 1971).

Jordan et al. (1991) summarized the literature supporting adoption of the Chesapeake Bay
restoration goal target concentration protecting anadromous spawning and nursery areas as
follows.

This target DO concentration [>5 mg/L at all times] was selected to protect the
early life stages of striped bass, white perch, alewife, blueback herring, American
shad, hickory shad, and yellow perch. This concentrations of DO will allow eggs

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to hatch normally (Bradford et al. 1968; O'Malley and Boone 1972; Marcy and
Jacobson 1976; Harre and Bayless 1981; Jones et al. 1988), as well as allow
survival and growth of larval and juvenile stages of all anadromous target species
(Tagatz 1961; Bogdanvo et al 1967; Krouse 1968; Bowker 1969; Chittenden
1969, 1972;, 1973; Meldrim etal. 1974; Rogers et al. 1980; Miller et al. 1982;

Coutant 1985; ASMFC 1987; Joneses al. 1988). For example, concentrations of
DO below 5 mg/L for any duration will not support normal hatching of striped
bass eggs (O'Malley and Boone 1972). Although one hatchery operation was able
to maintain striped bass fingerlings at DO concentrations of 3-4 mg/L (Churchill
1985; Loos 1991), Bowker et al. (1969) found DO >3.6 mg/L was required for
survival of juveniles.

Across an array of temperatures (13-25°C)and salinities (5-25 ppt), Krouse (1968),
observed complete mortality of striped bass at 1 mg/L, minimal mortality at 5 mg/L, and
intermediate survival at 3 mg/L upon exposure over 72 hours. Some field observations have
indicated that juveniles and adults of anadromous species prefer dissolved oxygen concentrations
6 mg/L (Hawkins 1979; Christie et al. 1981; Rothschild 1990). However, no lethal or sublethal
effects other than possible avoidance have been documented for dissolved oxygen concentrations
between 5 and 6 mg/L.

Rationale

The migratory spawning and nursery designated use criteria must also ensure full
protection for warmwater freshwater species' egg, larval and juvenile life stages which co-occur
with the tidal fresh and low salinity migratory spawning and nursery habitats. To ensure full
protection for resident tidal fresh warmwater species' early life stages, criterion values of a 7 day
mean of 6 mg/L and an instantaneous minimum of 5 mg/L were selected.

To ensure protection of not only survival and recruitment of larvae into the juvenile
population but also eliminate any potential for adverse impacts on growth during the critical
larvae and early juvenile life stages, a criterion value of an instantaneous minimum of 5 mg/L
was selected.

The Virginian Province saltwater criteria document states that exposures to dissolved
oxygen concentrations above this concentration will not result in any adverse impacts on growth.
Given the general lack of information on the population level consequences of short versus long
term reductions in growth on survival of larvae and juveniles, a specific averaging period was not
recommended in the Virginian Province saltwater criteria document. In the case of anadromous
species, there is narrow set of natural conditions (e.g., salinity, temperature) required and short
time window available for a successful spawn. Natural mortalities for larvae are already

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extremely high. As even short term reductions ingrowth could influence advancement to the
next stage through impairment of survival, ability to avoid predators, etc., the criterion value
protective against growth effects is applied as an instantaneous minimum.

This conservative allowable duration of exposure is completely consistent with the
instantaneous minimum duration for the 5 mg/L concentration criterion value from the EPA
freshwater dissolved oxygen criteria for ensuring full protection of warmwater freshwater
species' early life stages against short term exposures. The instantaneous minimum of 5 mg/L
criterion value fully protects against larval recruitment effects and provides protection for
survival and growth of sturgeon.

Migratory Spawning and Nursery Criteria

The following criteria are fully supportive of the Chesapeake Bay migratory spawning
and nursery designated use applied from the February 15th througho June 10th: a 7 day mean of 6
mg/L applied to tidal fresh waters with long term averaged salinities less than 0.5 parts per
thousand salinity; and an instantaneous minimum of 5 mg/L. From June 11th through February
14th, the shallow/open water designated use criteria will apply throughout the migratory spawning
and nursery designated use habitat. Please see Chesapeake Bay Tidal Waters Designated Uses
(Appendix A) for documentation on the selection of the February 15 through June 10 timeframe.

Shallow/Open Water Designated Use Criteria

Criteria supportive of the shallow/open water designated use must fully protect the
"propagation and growth of balanced, indigenous populations of ecologically, recreationally, and
commercially important fish, shellfish and underwater grasses inhabiting shallow/open water
habitats." The oxygen requirements for the species and communities inhabiting shallow and
open water habitats are similar enough to ensure protection of both habitat with a single set of
criteria. The shallow/open water criteria were based on establishing dissolved oxygen
concentrations protective against losses in larval recruitment, growth effects on larvae and
juveniles, and survival ofjuveniles and adults from tidal fresh to high salinity habitats.

Criteria Components

Protection Against Larval Recruitment Effects

Application of Virginian Province saltwater criteria larval recruitment effects model
generates a relationship illustrated as a curve, projecting the cumulative loss of recruitment
caused by exposure to low dissolved oxygen. The number of acceptable days of seasonal
exposure to low dissolved oxygen decreases as the severity of the low oxygen conditions
increase. The shallow/open water designated use criteria must ensure protection of larvae as they
recruit into the juvenile/adult population for species utilizing these habitats during their early life
stages.

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The Virginian Province saltwater criteria larval recruitment curve levels out at
approximately 4.6 mg/L beyond 30-40 days exposure (see Figure III-2). Dropping the non-
Chesapeake Bay resident species and then applying a series of Chesapeake Bay specific
modifications to the larval recruitment model parameters as described previously yields a curve
which closely follows the original Virginian Province saltwater criteria curve, but which levels
out around 4.7 mg/L. Dissolved oxygen concentrations/exposure durations falling the above the
curve would be protective against larval recruitment effects.

Protection Against Growth Effects

To ensure recruitment to the adult population, the Bay criteria must ensure protection
against growth effects on rapidly developing larvae and juvenile. The Virginian Province
saltwater criteria document recommends 4.8 mg/L as the threshold above which long-term,
continuous exposures should not cause unacceptable growth effects. When the non-Chesapeake
Bay species are removed from the Virginian Province saltwater criteria dissolved oxygen growth
effects data base, the recalculated Bay specific criterion protective against growth effects is 5.0
mg/L.

Protection of Juvenile/Adult Survival

The Virginian Province saltwater criteria document recommends 2.27 mg/L as the
threshold above which long-term, continuous exposures should not cause lethal conditions for
juvenile and adult fish and shellfish. When the non-Chesapeake Bay resident species are
removed from the extensive EPA saltwater criteria low dissolved oxygen effects database, the
recalculated criterion protective of juvenile/adult survival is 2.24 mg/L.

Protection of Resident Tidal Fresh Species

The shallow/open water designated use criteria must also ensure full protection for
warmwater freshwater species which co-occur within tidal fresh and low salinity shallow and
open water habitats. The EPA freshwater dissolved oxygen criteria set a 30 day mean of 5.5
mg/L; 7 day mean minimum of 4.0 mg/L; and 1 day instantaneous minimum of 3.0 mg/L for the
protection of life stages for warmwater species beyond early life stages (U.S. Environmental
Protection Agency 1986).

Protection Against Effects on Threatened/Endangered Listed Species

Short term exposures to dissolved oxygen concentrations of >3.5 mg/L and longer term
exposures to > 5mg/L would provide protection for survival and growth of Atlantic and
shortnose sturgeon (Secor and Niklitschek 2001).

Scientific Literature

As striped bass larvae begin to metamorphose to the juvenile stage, these fish begin

23

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moving into shallow water habitats nearshore and within shoal areas of less than six feet deep
(Boreman and Klauda 1988, Boynton et al. 1981; Setzler-Hamilton 1981). Nursery areas for
juvenile striped bass with dissolved oxygen concentrations > 5 mg/L are preferable given
findings that concentrations below 4 mg/L can adversely impair juvenile growth rates, feeding
rates, habitat use, and susceptibility to predation (Magnuson et al. 1985; Suthers and Gee 1986;
Kramer 1987; Poulin et al. 1987; Sanint Paul and Soares 1987; Breitburg et al. 1994) and
mortality of juveniles has been observed at dissolved oxygen concentrations < 3 mg/L
(Chittenden 1972; Coutant 1985; Krouse 1968). In the laboratory, Hill et al. (1981) observed
that when pH and dissolved solids were within favorable ranges, striped bass (Morone saxatilis)
avoided dissolved oxygen concentrations 4.9 mg/L.

Results from trawls in Long Island showed significant reductions in both species diversity
and abundance at sites with dissolved oxygen <2 mg/L (Howell and Simpson 1994). At sites
with dissolved oxygen concentrations >3 mg/L, 15 of the 18 target species caught occurred with
greater frequency compared with sites with concentrations <2 mg/L. Followup work indicated
total abundance of fish was relatively insensitive to low dissolved oxygen conditions, reaching
normal levels at 1.5 mg/L. However, total fish biomass and species richness were particularly
sensitive, declining at 3.7 mg/L and 3.5 mg/L, respectively (Simpson et al. 1995).

Rationale

To ensure full protection of survival and recruitment of larvae into the juvenile
population, reduce the potential for adverse impacts on growth, and protect for the survival of a
threatened/endangered species across tidal fresh to high salinity habitats, criteria values of a 30
day mean of 5 mg/L, 7 day mean of 4 mg/L, and an instantaneous minimum of 3.5 mg/L were
selected.

The 5 mg/L value is based on a recalculation of the Virginian Province saltwater criterion
protecting again growth impacts, (rounded up from 4.8 mg/L) using only Chesapeake Bay
species. The Virginian Province saltwater criteria document states that exposures to dissolved
oxygen concentrations above this concentration will not result in any adverse impacts on growth.
However, no specific duration was recommended within the criteria document. The extensive
shallow and open water habitats provide greater opportunities for escaping from predators,
seeking food, etc. then migratory spawning and nursery habitats. Impacts from short term
reductions in growth due to exposure to low dissolved oxygen should not adversely impact
recruitment of larvae and juveniles into the adult population. The 30 day mean averaging period
was selected to reflect current uncertainties about how much impact reduction in growth has on
juvenile and adult survival and reproduction in shallow and open water habitats in Chesapeake
Bay and its tidal tributaries as well as provide protection for larval recruitment. The 30 day mean
averaging period is consistent with and fully protective of effects against larval recruitment (see

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CHESAPEAKE BAY DISSOLVED OXYGEN CRITERIA

WORKING DRAFT No. 1 July 3, 2001

Figure III-3 and text below).

The instantaneous minimum 3.5 mg/L criterion provides protection against lethal effects
from short term exposures to low dissolved oxygen for sturgeon—both Atlantic and shortnose.
A 30 day mean 5 mg/L criterion provides protection against growth effects for longer term
exposures. Application of the 3.5 mg/L minimum as an instantaneous concentration is justified
on the basis that effects on shortnose sturgeon were observed after just 6 hours exposure (Jenkins
et al. 1994).

The combination of criterion values of a 30 day mean 5 mg/L, a 7 day mean of 4 mg/L,
and a 1 day instantaneous minimum 3.5 mg/L are fully protective of larval recruitment.
Depending on an assumption of partial or 100 percent exposure to low dissolved oxygen
concentrations, larval recruitment would be protected at concentrations ranging between 4.6 and
4.8 mg/L beyond 30 days exposure (Figure M-3). At 7 days exposure, concentrations between

3.4 and 3.8 mg/L extracted from the range of larval recruitment curves, would be protected by the
4 mg/L concentration criterion value. The instantaneous minimum 3.5 mg'L criterion would be
protective of the range of larval recruitment concentrations between 2.7-3.1 mg/L calculated at
the 1 day exposure level.

The 5 mg/L concentration value and the 30 mean day minimum temporal application
period are consistent with, but slightly less protective than the EPA freshwater dissolved oxygen
criteria document's recommended 30 day mean of 5.5 mg/L for protection of warmwater
freshwater species (U.S. Environmental Protection Agency 1986). The other two components of
the proposed shallow/open water criteria—7 day mean 4 mg/L and 1 day instantaneous minimum

3.5 mg/L—are fully consistent with the EPA freshwater warmwater criteria, with the 3.5 mg/L
slightly more protective than its corresponding warmwater freshwater criterion value of 3 mg/L.

Shallow/Open Water Criteria

The following criteria are fully supportive of the Chesapeake Bay shallow/open water
designated uses when applied year round: 30 day mean of 5 mg/L; 7 day mean of 4 mg/L; and an
instantaneous minimum of 3.5 mg/L.

Deep Water Designated Use Criteria

Within deeper water habitats, where physical exchange of higher oxygenated waters in
the upper water column habitats is largely prevented by density and thermal stratification,
dissolved oxygen concentrations will naturally be lower thai would be expected under fully
saturated conditions during the warmer months of the year. Criteria supportive of the deep water
designated use must fully protect the propagation and growth of balanced, indigenous
populations of ecologically, recreationally, and commercially important fish and shellfish species

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WORKING DRAFT No. 1 July 3, 2001

that depend on these deeper water habitats for location of prey and shelter at sometime
throughout the year.

Within Chesapeake Bay, the bay anchovy (Anchoa mitchilli) is an abundant, ecologically
significant fish likely to be impacted directly by low to no dissolved oxygen conditions given its
life history. Not a commercially exploited species, bay anchovy are a major prey for bluefish,
weakfish, and striped bass (Hartman and Brandt 1995), forging 1he link between zooplankton and
predatory fish (Baird and Ulanowicz 1989) and representing from 60 to 90 percent of piscivorus
fish diets on a seasonal basis (Hartman 1993). Bay anchovy spawn from May to September
within the Bay, with a peak in June-July (Olney 1983; Dalton 1987) across abroad range of
temperatures and salinities throughout Chesapeake Bay (Dovel 1971; Houde and Zastrow 1991).
Their spawning and nursery periods directly coincide with the presence of low dissolved oxygen
conditions in Chesapeake Bay and its tidal tributaries.

Hatchability of fish eggs is known to be influenced by the oxygen concentrations to
which the eggs are exposed during incubation (reviewed by Rombough 1988). Chesney and
Houde (1989) conducted laboratory experiments to test the effects of low dissolved oxygen
conditions on the hatchability and survival of bay anchovy eggs and yolk-sac larvae. Their
findings demonstrated that survival rates of bay anchovy eggs and larvae are likely to be affected
when exposed to dissolved oxygen concentrations less than 3 mg/L and 2.5 mg/L, respectively.
Breitburg (1994) found very similar effects for 3-13 day post hatch bay anchovy larvae where 50
percent survival was observed at 2.1 mg/L.

Bay anchovy routinely inhabit waters around the pycnocline. Their larvae are found
throughout the water column when bottom oxygen concentrations are above 2 mg/L (Keister et
al. 2000). Bay anchovy eggs are found throughout the water regardless of bottom layer
concentration in mesohaline areas of tributaries (Keister et al. 2000), but may be retained in
surface waters in the mesohaline mainstem Bay (E. North and E. Houde, unpublished data;
Breitburg et al. unpublished data). MacGregor and Houde (1996) also found that most bay
anchovy eggs were distributed in above pycnocline waters when subpycnocline waters had
dissolved oxygen concentrations of <2 mg/L. Rilling and Houde (1999) observed bay anchovy
eggs and larvae distributed through out the water column during a June-July time frame. In areas
of the mainstem Bay where bay anchovy eggs might be more limited to the surface and
pycnocline layers, sciaenid eggs are abundant in the bottom layer of the water column (E. North
and E. Houde, unpublished data; Breitburg et al. unpublished data). However, the dissolved
oxygen requirements of sciaenid eggs are not known.

Environmental conditions present during and events that take place in the egg, larvae
and/or juvenile life stages strongly influence fish population dynamics. Key among these are

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WORKING DRAFT No. 1 July 3, 2001

changes in food supply to first-feeding larvae and factors that modify predation on the highly
vulnerable larval life stages. Given the majority of the species for which larval effects data are
available within the Virginian Province saltwater criteria document will not be found in
pycnocline and subpycnocline waters, a larval recruitment effects model was generated for bay
anchovy as the basis for deriving criteria protective of deep water habitats.

Criteria Components

Protection Against Egg/Larval Recruitment Effects

Two larval recruitment effect models were derived specific to Chesapeake Bay bay
anchovy. The bay anchovy eggs effects model was based on a 5 percent impairment of eggs
hatching to yoke-sac larvae, assuming a 100 day recruitment period and one-day development
period based on the work of Chesney and Houde (1989). The larvae-based recruitment effects
model, also based on a 5 percent impairment, assumed that yoke-sac larvae and "regular" larvae
had the same sensitivity. A development period of 32 days was applied based on work by Houde
1987 where he stated an egg to larval duration of 33 days. One day was subtracted to reflect the
egg stage (Chesney and Houde 1989) yielding the 32 day development period. A 132
recruitment period was calculated by adding the 32 day development period with the 100
recruitment period from above. A 50 percent exposure to low dissolved oxygen concentrations
was built into both the eggs and larvae recruitment effects models given the field-based
observations of widespread distributions of eggs and larvae across Bay mainstem waters and
throughout the water column except in deep subpycnocline waters with extremely low dissolved
oxygen concentrations (Keister et al. 2000; MacGregor and Houde 1996; Rilling and Houde
1996). The final survival curves for both the egg and larvae recruitment effect models were
based on matching the effects data from Chesney and Houde (1989) with the final survival curve
from Figure 5 in the Virginian Province saltwater criteria document (Figure III-4).

Scientific Literature

Breitburg et al. (2001) provided an excellent synthesis of the acute sensitivities of an
array of species that may inhabit water column or near bottom habitats within the deep water
designated use habitats.

Adults and juveniles of most Chesapeake Bay species that have been tested have
24 hr LC50 values near 1 mg l"1 (i.e., approximately 13% saturation at 25°C and 18
psu). Acute toxicity tests have yielded 50% mortality rates with 24-hr exposures
at 0.5-1.0 mg l"1 for species such as hogchoker (Trinectes maculatus), northern sea
robin (Prionotus carolinus), spot (Leiostomus xanthurus; but LC50 reported as >1
mg l"1 by Phil et al. 1991) tautog (Tautoga onitis), windowpane flounder
(,Scopthalmus aquosus), and fourspine stickleback (Apeltes quadracus), and 50%
mortality rates between 1.1 and 1.6 mg l"1 for Atlantic menhaden (Brevoortia

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WORKING DRAFT No. 1	July 3, 2001

tyrannus), scup (Stenotomus chrysops), summer flounder (Paralichthyus
dentatus), pipefish (Syngnathus fuscus), and striped bass (Morone saxatilis) (Pihl
et al. 1991; Poucher and Coiro, 1997; Thursby et al. 2000). Thus for nearly all
species tested, the range of tolerances is quite low; only a 1.0 mg l"1 difference
separates the most and least sensitive species described above.

Although fewer species have been tested during the larval stage, larvae of species
that occur in Chesapeake Bay appear to be somewhat more sensitive to low
oxygen exposure than are most adults and juvenile. For example, 50% mortality
with 24-h exposure occurs between 1.0 and 1.5 mg l"1 for skilletfish (Gobiesox
strumosus), naked goby (Gobiosoma bosc), and inland silverside (Menidia
beryllina) larvae, while 50% mortality occurs at 1.8 to 2.5 mg l"1 for larval red
drum (Sciaenops ocellatus), bay anchovy (Anchoa mitchilli), striped blenny
(¦Chasmodes bosquianus) and striped bass (Saksena and Joseph 1972; Breitburg
1994; Poucher and Coiro 1997). Field and laboratory observations indicate that
lethal dissolved oxygen concentrations for skilletfish, naked goby, and striped
blenny adults are 1.0 mg l"1 (Breitburg unpublished data).

Embryo tolerances vary inconsistently in relation to tolerances of later stages;
50% mortality in 12-96 h occurs at a higher dissolved oxygen concentration than
that for larval mortality for bay anchovy (2.8 mg l"1), at a similar oxygen
concentration as for larvae for inland silverside (1.25 mg l"1), and at lower
concentrations than that leading to larval mortality for winter flounder
(.Pleuronectes americanus; 0.7 mg l"1) and naked goby (approximately 0.6 mg l"1)
(Chesney and Houde 1989; Poucher and Coiro 1997).

Roman et al. (1993) examined the distribution of the copepods, Acartia tonsa and
Oithona colcarva through the water column in Chesapeake Bay. Acartia tonsa, which regularly
migrates from open water down to sub-pycnocline bottom waters, were not found in bottom
waters when oxygen concentration were < 1 mg/L. The highest concentration of zooplankton
were found at the pycnocline.

In a recent review of zooplankton responses to and ecological consequences of
zooplankton exposure to low dissolved oxygen, Marcus (2001) synthesized the following
literature findings.

Vargo and Sastry (1977) reported that 2-h LD50 values for Acartia tonsa and
Eurytemora affinis adults collected from the Pettaquamscutt River Basin, Rhode
Island ranged from dissolved oxygen concentrations of 0.36 to 1.40 mg l"1 and

28

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WORKING DRAFT No. 1 July 3, 2001

0.57 to 1.40 mg l"1 respectively. Roman et al. (1993) tested the oxygen tolerance
of adults of Acartia tonsa and Oithona colcarva from Chesapeake Bay. Survival
was considerable less after 24 h in < 2.0 mg l"1 oxygenated water.

Stalder and Marcus (1997) examined the 24-h survival of three coastal copepod
species in response to low oxygen. Acartia tonsa showed excellent survival at
concentrations as low as 1.43 mg 1-1. Between 1.29 and 0.86 mg l"1 survival
declined markedly and at 0.71 mg l"1 mortality was 100%. Labidocera aestiva
and Centropages hamatus were more sensitive to reduced dissolved oxygen
concentrations. The survival of these species was significantly lower at 1.43 mg 1"

The survival of nauplii of Labidocera aestiva and Acartia tonsa at low
dissolved oxygen concentrations was generally better than adult survival.

Rationale

Protection of the recruitment of bay anchovy eggs and larvae into thejuvenile/adult
population is of critical importance to the integrity of the Chesapeake Bay ecosystem. Bay
anchovy play a critical ecological role as a prime source of food for many higher level predator
fish species. To protect bay anchovy recruitment, criteria values of a 30 day mean of 3 mg/L and
an instantaneous minimum of 1.7 mg/L were selected to best reflect the shape of the combined
bay anchovy egg and larval recruitment curves (Figure III-5).

Chesney and Houde (1989) evaluated 12-14 hour old yolksac bay anchovy larvae over an
exposure treatment of 12 hours, yielding the effects data used in running the bay anchovy
egg/larval recruitment models. In deep water habitats, field observations support the presence of
effects at durations less than 24 hours supporting the selection of an instantaneous minimum vs.
daily averaged minimum criterion concentration (Breitburg 1992). Given the reported laboratory
and field effects were manifested in less than a half a day, an instantaneous minimum
concentration versus a daily averaged minimum concentration was selected as the temporal
period for application of the 1.7 mg/L criterion value.

The Virginian Province saltwater criterion protecting juvenile/adult survival recalculated
to factor in only Chesapeake Bay species—2.24 mg/L—is overprotective of species inhabiting
deep water habitats given the majority of the species used in calculation of this criterion value
principally inhabit shallow and open water habitats. The instantaneous minimum of 1.7 mg/L
will ensure protection of bay anchovy early life stages as well as juvenile and adult survival of
fish species commonly inhabiting pycnocline and sub-pycnocline habitats for which effects data
were available (e.g., spot, summer flounder, winter flounder) (see Table 1 on page 8 in U.S.
Environmental Protection Agency 2000). This criterion value will also protect zooplankton
located in deep water habitats, the principal prey of bay anchovy and many other fish during their

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WORKING DRAFT No. 1	July 3, 2001

early life stages.

Recommended Criteria

The following criteria are fully supportive of the Chesapeake Bay deep water designated
sue when applied from May through September: 30 day mean of 3 mg/L; and an instantaneous
minimum of 1.7 mg/L. From October through April, the shallow/open water designated use
criteria will apply throughout the deep water habitat given full mixing of the water column in the
absence of stratification.

Deep Channel Designated Use Criteria

Criteria supportive of the deep channel designated use must fully protect deep channel
habitats as a "refuge for balanced, indigenous populations of ecologically, recreationally, and
commercially important fish species that depend on deep channel habitats for overwintering"
during the months of October through April. From May through September, the criteria must
protect the propagation and growth of benthic infaunal and epifaunal worms and clams that
provide food for bottom feeding fish and crabs. The seasonal-based deep channel criteria are
based on establishing dissolved oxygen concentrations protective of survival of bottom sediment
dwelling worms and clams as well as survival of larger predator fish during the cooler months of
the year.

Deep channel habitats are defined as the very deep water column and adjacent bottom
surficial sediment habitats located principally in the river channel at the lower reaches of the
major rivers and along the spine of the upper and middle mainstem Bay at depths below which
where seasonal anoxic (no oxygen) to severe hypoxic conditions (< 2 mg/L dissolved oxygen)
routinely set in. From late spring to early fall, much of these deep channel habitats are exposed
to very low to no dissolved oxygen concentration conditions. Under these extremely low
dissolved oxygen conditions of 1-2 mg/L, these habitats are suitable only for survival and
propagation of benthic infaunal and some epifaunal organisms. During the cooler months of the
year, these deep channel habitats are important to both bottom forging blue crabs and larger
finfish species (e.g., striped bass, white perch, croaker, sturgeon) seeking refuge in these deeper,
warmer waters.

Components

Protection of Bottom Dwelling Community Survival

Benthic infauna have high tolerances to low dissolved oxygen conditions (>1 mg/L) with
observations that many macrofaunal species demonstrate behavioral reactions before they
eventually die (Diaz and Rosenberg 1995). For the mesohaline zone of estuaries, the critical
dissolved oxygen level appears to be around 0.6 - 1.0 mg/L (Diaz and Rosenberg 1994) (Table
III-5). At the high aid of the dissolved oxygen range, the bottom dwelling community starts to

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CHESAPEAKE BAY DISSOLVED OXYGEN CRITERIA

WORKING DRAFT No. 1 July 3, 2001

lose moderately tolerant species, with more tolerant species dying off at the low end of the range.
In estuaries and coastal systems exposed to seasonally varying low dissolved oxygen, the critical
dissolved oxygen concentration is closer to 1 mg/L (Llanso 1992), with subtle reductions in
dissolved oxygen concentration from 1 to 0.5 mg/L causing the full range of
responses-behavioral to death (Llanso and Diaz 1994). In their synthesis of dissolved oxygen
concentrations causing acute and chronic effects on Chesapeake Bay benthic infaunal organisms,
Holland et al. (1989) found a similar range of oxygen concentrations causing mortality or severe
behavioral effects (Table III-6). In the deep channel regions of the Chesapeake Bay, classic
opportunistic mud communities of burrowing worms and clams of species demonstrating broad
tolerance of a wide range of sediment types, salinities, dissolved oxygen concentrations, and
organic loadings. Several keystone Bay species- Paraprionospio pinnata, Streblospio benedicti,
Loimia medusa, and Heteromastus filiformis are all resistant to dissolved oxygen concentrations
down to 0.6 mg/L (Diaz et al. 1992; Llanso and Diaz 1994; Llanso 1991).

Extensive mortality is likely only under persistent exposure to very low dissolved oxygen
concentrations (< 1 mg/L) at higher summer temperatures in Chesapeake Bay (Holland et al.
1977) with similar findings reported for other estuarine and coastal systems (Rosenberg 1977;
Jorgensen 1980; Stachowitsch 1984; Gaston 1985).

While the macrobenthic community itself is often found to be insensitive to low
dissolved oxygen concentrations around 2 mg/L, exposure of these bottom habitats to brief
periods of dissolved oxygen concentrations <2 mg/L affects behavior (decreased burrowing
depth and exposure at the sediment surface), growth and production (Diaz et al. 1992). Demersal
feeding fish changed their feeding habits quickly to take advantage of stressed macrobenthos that
came to the sediment surface (Jorgensen 1980; Stachowitsch 1984), where they become more
vulnerable to predation during or following a low dissolved oxygen event (Pihl et al. 1991; Pihl
et al. 1992).

Epifaunal communities living along the surfaces of the bottom sediments in Chesapeake
Bay can persist with minimal changes in species composition and abundance under brief
exposures to dissolved oxygen concentrations in the range of 0.5-2.0 mg/L (Sagasti et al. 2000).

Protection of Winter Refuge Habitat

These habitats are important to both bottom foraging blue crabs and larger finfish species
seeking refuge in these deeper, warmer waters (e.g., striped bass, white perch, Atlantic croaker,
shortnose sturgeon, and Atlantic sturgeon) during the cooler months of the year (see Appendix
A). The previously described shallow/open water criteria will provide the necessary levels of
protection for all of these species, for both juvenile and adult life stages.

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WORKING DRAFT No. 1	July 3, 2001

Rationale

To ensure protection of the survival of bottom dwelling worms and clams, a one day
instantaneous minimum of 1 mg/L criterion was selected. As documented through the extensive
scientific literature, this value will protect against lethal effects from exposure to low dissolved
oxygen. However, behavioral changes leading to increased opportunities for predation are not
protected by this criterion value. These behavioral changes may provide a benefit to bottom
feeding fish and crabs by providing direct access to food albeit under potential stressful water
quality conditions. To ensure protection of the survival and growth of fish species inhabiting
deep channel habitats during the cooler months of the year, the shallow/open water criteria values
will be applied.

Deep Channel Criteria

The following criteria are fully supportive of the Chesapeake Bay seasonal-based deep
water designated use: an instantaneous minimum of 1 mg/L from May through September and a
30 day mean of 5 mg/L, 7 day mean of 4 mg/L, and an instantaneous minimum of 3.5 mg/L from
October through April.

Chesapeake Bay Dissolved Oxygen Criteria

[EDITOR'S NOTE: NEED TO ADD SOME INTRODUCTORY TEXT HERE.] The
Chesapeake Bay dissolved oxygen criteria are summarized in Table III-7.

32

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WORKING DRAFT No. 1	July 3, 2001

EDITOR'S NOTE: DISSOLVED OXYGEN CRITERIA IMPLEMENTATION WILL BE
ADDRESSED IN A SEPARATE CHAPTER IN THE FINAL CHESAPEAKE BAY CRITERIA
DOCUMENT. JUST THE OUTLINE OF THE DISSOLVED OXYGEN RELATED CRITERIA
IMPLEMENTATION TEXT IS PROVIDED BELOW. THE DISSOLVED OXYGEN
CRITERIA TEAM HAS BEEN FOCUSED TO DATE ON DERIVING THE WORKING
DRAFT CRITERIA DESCRIBED PREVIOUSLY. THE IMPLEMENTATION PROCEDURES
WILL BE FLESHED OUT OVER THE COURSE OF THE SUMMER. PLEASE IDENTIFY
IMPLEMENTATION ISSUES NOT OUTLINED BELOW AND PROVIDE
IDEAS/SUGGESTIONS/TEXT FOR HOW WE SHOULD ADDRESS THE
IMPLEMENTATION OF THESE BAY SPECIFIC DISSOLVED OXYGEN CRITERIA. THE
ULTIMATE OBJECTIVE IS TO DEVELOP A SET OF PROCEDURES THAT WILL BE
ADOPTED AND USED CONSISTENTLY ACROSS ALL BAY TIDAL WATERS BY THE
STATES AND ALL BAY RESTORATION PARTNERS.

VI. Recommended Implementation Procedures
Dissolved Oxygen Criteria Implementation
Defining Attainment

Spatial Application of the Criteria
Designated Use Habitat Delineations

	Defining Upper and Lower Pycnocline Depths

Determining Application of the Deep Water and Deep Channel Criteria
Translating Chesapeake Bay Water Quality Monitoring Data into Exposure Frequency
Application to Evaluation of Chesapeake Bay Water Quality Model Output
Determining Natural Excursions vs. Anthropogenic Causes

	High River Flow Events

	Pycnocline Seeching Events

	Natural Diel Fluctuations

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WORKING DRAFT No. 1	July 3, 2001

Monitoring Design/Implementation Considerations

34

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WORKING DRAFT No. 1 July 3, 2001

References

[EDITOR'S NOTE: THERE ARE STILL MISSING FULL CITATIONS AND MISSING
CITATIONS REFERENCED IN THE MAIN TEXT; THE NEXT DRAFT WILL HAVE A
FULL LISTING OF COMPLETE CITATIONS REFERENCED IN THE MAIN TEXT ALL
CONSISTENTLY FORMATTED.]

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Table III-l. Chesapeake Bay dissolved oxygen goal for restoration of living resource habitats.

The Chesapeake Bay dissolved oxygen goal for restoration of living resource habitats is to
provide for sufficient dissolved oxygen to support survival, growth, reproduction of
anadromous, estuarine, and marine fish and invertebrates in Chesapeake Bay and its tidal
tributaries by achieving, to the greatest spatial and temporal extent possible, the following
target concentrations of dissolved oxygen, and by maintaining the existing minimum
concentration of dissolved oxygen in areas of Chesapeake Bay and its tidal tributaries where
dissolved oxygen concentrations are above the recommended targets.

Target Dissolved Oxygen	Time and Location

1.0 mg/L dissolved oxygen 3.0 mg/L For no longer than 12 hours, interval between

excurisons at least 48 hours, everywhere

Monthly mean dissolved oxygen 5.0 mg/L All times, throughout above-pynocline waters

The pynocline is the porti on of the water column where densi ty changes rapidly because of salin ity and temperature.

Concentrations

Dissolved oxygen 1.0 mg/L

All times, everywhere

Dissolved oxygen 5 mg/L

All times, throughout above-pynocline waters
in spawning reaches, spawning rivers, and
nursery areas.

Source: Jordan et al. 1992.

48

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CHESAPEAKE BAY DISSOLVED OXYGEN CRITERIA

WORKING DRAFT No. 1	July 3, 2001

Table III-2. EPA Virginian Province saltwater dissolved oxygen criteria effects data base

species found in Chesapeake Bay.

Common Name

Scientific Name

Found in Chesapeake Bay

Notes

Species

Genus Only

American lobster

Homarus americanus

(Yes)

-

1

Amphipod

Ampelisca abdita

Yes

-



Atlantic menhaden

Brevoortia tyrannus

Yes

-



Atlantic rock crab

Cancer irroratus

Yes

-



Atlantic silverside

Menidia menidia

Yes

-



Atlantic surfclam

Spisula solidissima

(Yes)

-

2

Blue crab

Callinectes sapidus

Yes

-



Burry's octopus

Octopus burryi

No

Yes

4

Daggerblade grass shrimp

Palaemonetes pugio

Yes

-



Eastern oyster

Crassostrea virginica

Yes

-



Flatback mud crab

Eurypanopeus depressus

Yes

-



Fourspine stickleback

Apeltes quadracus

Yes

-



Green crab

Carcinus maenas

No

No

6

Hard clam

Mercenaria mercenaria

Yes

-



Harris mud crab

Rhithropanopeus harrisii

Yes

-



Inland silverside

Menidia beryllina

Yes

-



Longfin squid

Loligo pealeii

(Yes)

-

3

Longnose spider crab

Libinia dubia

Yes

-



Marsh grass shrimp

Palaemonetes vulgaris

Yes

-



Mysid

Americamysis bahia

No

No

7

Naked goby

Gobiosoma bosc

Yes

-



Northern sea robin

Prionotus carolinus

Yes

-



49

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CHESAPEAKE BAY DISSOLVED OXYGEN CRITERIA

WORKING DRAFT No. 1 July 3, 2001

Common Name

Scientific Name

Found in Chesapeake Bay

Notes

Species

Genus Only

Pipe fish

Syngnathus fuscus

Yes

Rock crab

Cancer irroratus

Yes

Sand shrimp

Crangon septemspinosa

Yes

Say mud crab

Dyspanopeus sayi

Yes

Scup

Stenotomus chrysops

Yes

Sheepshead minnow

Cyprinodon variegatus

Yes

Skillet fish

Gobiesox strumosus

Yes

Striped bass

Morone saxatilis

Yes

Striped blenny

Chasmodes bosquianus

Yes

Spot

Leiostomus xanthurus

Yes

Summer flounder

Paralichthys dentatus

Yes

Tautog

Tautoga onitis

Yes

Windowpane flounder

Scophthalmus aquosus

Yes

Winter flounder

Pleuronectes americanus

Yes

Notes;

1. Occasionally found in the Chesapeake Bay mouth region outside of the Bay bridge/tunnel during blue
crab winter dredge surveys.

2. Found near the Chesapeake Baymouth at high salinities.

3. Found in the region around the Chesapeake Bay mouth.

4. Octopus americanus is found in the higher salinity reaches of Chesapeake Bay.

5. Genus Dyspanopeus supercedes genus Neopanope (See Weiss, Howard. Marine Animals of Southern
New England and New York, State Geological and Natural History Survey of Connecticut, 1995.)

6. If found in the Chesapeake Bay, Carcinus maenas would be at the extreme southern edge of its range

(See Gosner, Kenneth. Field Guide to the Atlantic Seashore : Invertebrates and Seaweeds of the Atlantic
Coast from the Bay of Fundy to Cape Flatter as, Houghton Mifflin. Boston. 1979.). This species has not
been documented in A Comprehensive List of Chesapeake Bay Basin Species 1998.

7. Americamysis bahia supercedes Mysidopsis bahia. See Price WW, Heard RW, Stuck L. Observations
on the genus Mysidopsis Sars, 1864 with the designation of a new genus, Americamysis, and the
descriptions of Americamysis alleni and A. stucki (Peracarida:Mysidacea:Mysidae), from the Gulf of

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CHESAPEAKE BAY DISSOLVED OXYGEN CRITERIA

WORKING DRAFT No. 1	July 3, 2001

Mexico. Proc Biol Soc Wash 107:680-698. 1994.

Source: U.S. Environmental Protection Agency 1998.

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WORKING DRAFT No. 1	July 3, 2001

Table III-3. Original EPA saltwater dissolved oxygen criteria Virginian Province-wide larval
recruitment model parameter values and revised length of recruitment season and duration of
larval development values reflecting Chesapeake Bay specific conditions.

Species

Length of
Recruitment
Season
(days)1

Duration of

Larval
Development

(days)1

Initial
Cohort
Size

Attrition

Rate
(percent
per day)

Percentage
Population
Exposed to
Hypoxic
Event

Cancer (Rock Crab)

65/100

35/22

100

5%

20%

Dyspanopeus (mud crab)

66/90

21/17

100

5%

75%

Eurypanopeus (mud crab)

66/90

21/17

100

5%

75%

Homarus (lobster)

95

35/15

100

5%

20%

Libinia (spider crab)

66/80

21/6

100

5%

50%

Menidia (silverside)

42/150

14

100

5%

50%

Morone (striped bass)

49/70

28

100

5%

50%

Palaemonetes (grass
shrimp)

100/120

12/15

100

5%

50%

Sciaenops (red drum)

49/140

21

100

5%

50%

1 First value is the original Virginian Providence-wide value; the second value following the
slash mark is the Chesapeake Bay specific model parameter value.

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WORKING DRAFT No. 1	July 3, 2001

Table III-4. EPA freshwater water quality criteria for dissolved oxygen for warmwater species.

Duration

Early Life Stages1

Other Life Stages

30 Day Mean

NA2

5.5

7 Day Mean

6

NA

7 Day Mean Minimum

NA

4

1 Day Minimum

5

3

1	Includes all embryonic and larval stages and all juvenile forms to 30-days following
hatching.

2	Not applicable.

3	All minimua should be considered as instantaneous concentrations to be achieved at all
times.

Source: U.S. Environmental Protection Agency. 1986.

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WORKING DRAFT No. 1	July 3, 2001

Table III-5. Response patterns of Chesapeake Bay benthic organisms to declining dissolved
oxygen concentrations.	

Response

Dissolved Oxygen
(mg/L)

Species

Reference

Avoidance

Infaunal swimming

1.1

Paraprionospio pinnata

Diaz et al. 1992

Fauna unable to leave or escape initiate a series of sublethal responses

Cessation of
feeding

0.6

Streblospio benedicti

Llanso 1991

1.0

Loimia medusa

Llanso and Diaz
1994

1.1

Capitella sp.

Warren 1997; Forbes
and Lopez 1990

Decreased activities
not related to
respiration

1.0

Streblospio benedicti

Llanso 1991

Cessation of
burrowing

1.1

Capitella sp.

Warren 1997

Emergence from
tubes or burrows

0.1-1.3

Ceriathiopis americanus

Diaz, unpublished
data

0.7

Micropholis atra

Diaz et al. 1992

10% saturation

Nereis diversicolor

Vismann 1990

Siphon stretching
into water column

0.1-1.0

Mya arenaria, Abra alba

Jorgensen 1980

Source: Diaz and Rosenberg 1995.

54

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WORKING DRAFT No. 1	July 3, 2001

Table III-6. Summary of literature on the tolerance of macrobenthic species found in Chesapeake Bay to low dissolved oxygen
conditions.

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE

Mollusca



Abra alba

Adult

0

10

LD50 in 200 hrs
(8.3 days)

Stickle et al.

(Submitted manuscript)



Adult

0

10

LD50 in 200 hrs

Dries and Theede 1974

Cardium edule

Adult

0

10

50% mortality in 7 days

Thamdrup 1935
referenced in O'Connor
(unpublished manuscript)



Adult

0.15

10

50% mortality in 102 hr (4.3
days) without sulfide, 96 hr
(4 days) with sulfide (50
mg/L Na2S.9H20

Theede et al. 1969; Theede
1973

Carium lamarki

Adult

0

10

LD50 in - 220 hr (9.2 days)

Dries and Theede 1974

Littorina
littoria

Adult

0.15

10

LD50 in 365 hr (15.2 days)
without sulfide, 180 hr (7.5
days) with sulfide;

50 mg/L

Theede et al. 1969; Theede
1973

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WORKING DRAFT No. 1	July 3, 2001

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE

Littorina
saxatilus

Adult

0.15

10

LD50 in 365 hr (15.2 days)
without sulfide, 72 hr (3
days) with sulfide;
50 mg/L

Theede et al. 1969; Theede
1973

Macoma
balthica

Adult

0

10

4 % mortality in 7 days

Thamdrup 1935; referenced in
O'Conner (unpublished
manuscript)



Adult

0

10

LD50 in 500 hr (20.8 days)

Dries and Theede 1974

Mercenaria

Larvae

0.9-2.4

25

Reduced growth

Morrison 1971

mercenaria



0.2

25

100% mortality in 14 days

Morrison 1971





0.9

25

0% mortality in 14 days

Morrison 1971



Juvenile
/Adult
(31-38
mm)

5.7

19-24

Maximum burrowing rate

Savage 1976





0.9-1.8

17-24

Reduced burrowing rate

Savage 1976





0.9

19

No mortality in 21 days and
30 days (two trials)

Savage 1976

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CHESAPEAKE BAY DISSOLVED OXYGEN CRITERIA

WORKING DRAFT No. 1	July 3, 2001

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE

Mulina lateralis

Juvenile
(5 mm)

0

10

LT50 in 10.5 days without
sulfide, 4.3 days with
sulfide; 644 mg/L
Na2S.9H20

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)





0

20

LT50 in 7.5 days

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)

Mulina lateralis



0

30

LT50 in 2 days

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)



Adult
(10 mm)

0

10

LT50 in 10 days without
sulfide, 3.8 days with
sulfide; 644 mg/L
Na2S.9H20

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)





0

20

LT50 in 2.5 days

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)





0

30

LT50 in 1.8 days

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)

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WORKING DRAFT No. 1	July 3, 2001

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE

Mya arenaria



0

"very low"

Survived for "weeks"

Collip 1921; referenced in
O'Conner (unpublished
manuscript)



0

14

Survived 0 8 days

Collip 1921; referenced in
O'Conner (unpublished
manuscript)



0

31

Survived - 1 day

Collip 1921; referenced in
O'Conner (unpublished
manuscript)

Mya arenaria

Adult

0.2

10

LC50 in 21 days without
sulfide, 17 days with sulfide;
referenced in O'Conner
(unpublished manuscript)

Theede et al. 1969; Theede
1973

Mytilus edulis

Adult

0.2

10

LC50 in 35 days without
sulfide, 25 days withsulfide;
referenced in O'Conner
(unpublished manuscript)

Theede et al. 1969; Theede
1973

Adult

0

10

20% mortality in 7 days

Thamdrup 1935; referenced in
O'Conner (unpublished
manuscript)

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WORKING DRAFT No. 1	July 3, 2001

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE

Spisula
solidissima

Adult

(49064

mm)

5.3-6.0

11-22

Maximum burrowing rate

Savage 1976





0.8-1.6

11-22

Reduced burrowing rate,
mortality

Savage 1976





1.6

21.7

1 of 9 dead in 5 days

Savage 1976





0.9

21.0

3 of 9 dead in 5 days

Savage 1976



Juvenile
/Adult
(31-
28mm)

5.7

19-24

Maximum burrowing rate

Savage 1976





0.9-1.8

17-24

Reduced burrowing rate

Savage 1976

Spisula
solidissima



0.9

19

No Mortality in 21 days and
30 days (two trials)

Savage 1976

Mulinia
lateralis

Juvenile
(5 mm)

0

10

LT50 in 10.5 days without
sulfide, 4.3 with sulfide; 644
mg/L Na2S.9H20

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)

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WORKING DRAFT No. 1	July 3, 2001

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE





0

20

LT50 in 7.5 days

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)





0

30

LT50 in 2 days

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)



Adult
(10 mm)

0

10

LT50 in 10 days without
sulfide, 3.8 days with
sulfide; 644 mg/L
Na2S.9H20

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)





0

20

LT50 in 2.5 days

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)





0

30

LT50 in 1.8 days

Shumway and Scott 1983;
referenced in O'Conner
(unpublished manuscript)



Adult

(100

mm)

1.0

10

LC50 in 15 days; initial
mortality in 8 days; total
mortality in 30 days

Thurberg and Goodlett 1979

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WORKING DRAFT No. 1	July 3, 2001

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE

Mulinia
lateralis



3.0

10

No mortality in 2 months

Thurberg and Good lett 1979

Juvenile
/Adult
3.7-5
cm)

1.0

10

LC50 in 7 days

Thurberg and Goodlett 1979

Juvenile
/Adult
(3.8-4.6
cm)

2.0

10

LC50 in 21 days

Thurberg and Goodlett 1979

Polychaeta

Capitella
capitata

Adult

0

12

Mortality in 8 days

Jacubowa and Malm 1931;
referenced in O'Conner
(unpublished manuscript)

Capitomastus
minimus

Adult

0

12

Mortality in 8 days

Jacubowa and Malm 1931;
referenced in O'Conner
(unpublished manuscript)

Etoeone picta

Adult

0

12

Mortality in 6 days

Jacubowa and Malm 1931;
referenced in O'Conner
(unpublished manuscript)

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WORKING DRAFT No. 1	July 3, 2001

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE

Glycera
convoluta

Adult

0

12

Mortality in 10 days

Jacubowa and Malm 1931;
referenced in O'Conner
(unpublished manuscript)

Harmothae
incerta

Adult

0

12

Mortality in 5 days

Jacubowa and Malm 1931;
referenced in O'Conner
(unpublished manuscript)

Nephtys ciliata

Adult

0

10

LD50 in 140 hr (5.8 days)

Dries and Theede 1974

Nerevis
diversicolor

Adult

0.2

10

LC50 in 5 days without
sulfide, 4 days with sulfide;
referenced in O'Conner
(unpublished manuscript)

Theede et al. 1969; Theede
1973

Adult

0

10

LD50 in 120 hr (5 days)

Dries and Theede 1974

Adult

0

6-8

72 hr with no mortality, ATP
conc. 59% of initial value
(after 72 hr); energy charge +
0.70(c)

Schottler 1979

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WORKING DRAFT No. 1	July 3, 2001

SPECIES

LIFE
STAGE

DISSOLVE
D OXYGEN
(MG/L)

TEMPERATURE
(°C)

OBSERVED RESPONSE

REFERENCE

Nereis pelagica

Adult

0

6-8

40% mortality after 36 hr;
ATP conc. 51% of initial
value (after 72 hr); energy
charge + 0.66(c)

Schottler 1979

Nereis virens

Adult

0

6-8

72 hr with no mortality, ATP
conc. 57% of initial value
(after 72 hr); energy charge +
0.77(c)

Schottler

Pectinaria
neapolitana

Adult

0

12

Mortality in 8 days

Jacubowa and Malm 1931;
referenced in O'Conner
(unpublished manuscript)

Terebellides
stroemi

Adult

0

10

LD50 in 72 hr (3 days)

Dries and Theede 1974

Source: Holland et al. 1989.

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WORKING DRAFT No. 1	July 3, 2001

Table III-7. Chesapeake Bay dissolved oxygen criteria..

Designated Use

Criteria Concentration/Duration

Temporal Application

Migratory spawning
and nursery

7 day mean of 6 mg/L1

February 15th - June 10th

Instantaneous minimum of 5 mg/L

30 day mean of 5 mg/L

June 11th - February 14th

7 day mean of 4 mg/L

Instantaneous minimum of 3.5 mg/L

Shallow/open water

30 day mean of 5 mg/L

All year round

7 day mean of 4 mg/L

Instantaneous minimum of3.5 mg/L

Deeper water

30 day mean of 3 mg/L

April through September

Instantaneous minimum of 1.7 mg/L

30 day mean of 5 mg/L

October through March

7 day mean of 4 mg/L

Instantaneous minimum of 3.5 mg/L

Deep channel

Instantaneous minimum of 1 mg/L

April through September

30 day mean of 5 mg/L

October through March

7 day mean of 4 mg/L

Instantaneous minimum of 3.5 mg/L

1. Applied to tidal fresh waters with long term averaged salinities less than 0.5 parts per
thousand.

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WORKING DRAFT No. 1 July 3, 2001

Appendix B.

Evaluation of Listed Threatened and Endangered Species within the

Chesapeake Bay and Tributary Tidal Waters and Implications for

Derivation of Bay Specific Dissolved Oxyen, Chlorophyll a and Water Clarity Criteria

Background

The Chesapeake Bay Program's Water Quality Standards Coordinators Team requested a
full evaluation of the level of protection afforded by the proposed Chesapeake Bay dissolved
oxygen, chlorophyll a and water clarity criteria for threatened and endangered species inhabiting
tidal waters. The following evaluation was prepared by Wayne Dengal, U.S. EPA Chespeake
Bay Program Office, with the assistance of the mid-Atlantic region U.S. Fish and Wildlife and
NOAA National Marine Fisheries Service endangered species coordinators and Jackie Johnson,
Interstate Commission on the Potomac River Basin and the Chesapeake Bay Program living
Resources Data Manager.

Information Sources

The U.S. Fish and Wildlife Service maintains the Threatened and Endangered Species
System (TESS), an online posting of federally-listed threatened and endangered species. The
web list is updated frequently, and includes species under the jurisdiction of the NOAA National
Marine Fisheries Service. Endangered species listings can be broken down and viewed state by
state. The world wide web address for TESS is : http://ecos.fws.gov/webpage/.

Evaluation Approach

On October 12, 2000, federally-listed species for Maryland, Virginia, Delaware and
District of Columbia (Table B-l) were referred to Jacqueline Johnson, Living Resources Data
Manager at the Interstate Commission on the Potomac River Basin, Chesapeake Bay Program
Office, Annapolis MD. Ms. Johnson reviewed the species list and compiled a short list of
aquatic fauna inhabiting Chesapeake Baytidal waters (Table B-2) using the document^
Comprehensive List of Chesapeake Bay Basin Species 1998 as her principal reference4.

Findings

The only species from combined Bay states lists whose habitat would be directly
influenced by state adoption of the proposed three criteria is the shortnose sturgeon (Acipenser
brevirostrum). Charisa Morris, Biologist (Threatened and Endangered Species Branch, U.S.
Fish and Wildlife Service, Chesapeake Bay Field Office, Annapolis MD) and Rod Schwarm,

4 U.S. Environmental Protection Agency. 1998. A Comprehensive List of Chesapeake
Bay Basin Species 1998. EPA 903R-98-013. Chesapeake Bay Program. Annapolis, MD.

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CHESAPEAKE BAY DISSOLVED OXYGEN CRITERIA

WORKING DRAFT No. 1	July 3, 2001

Biologist (NOAA National Marine Fisheries Service, Oxford Cooperative Laboratory, Oxford
MD) have confirmed that the shortnose sturgeon is the only endangered fish species in the
Chesapeake Bay and tidal tributaries.

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WORKING DRAFT No. 1	July 3, 2001

Bay Criteria Implications

Recent studies indicate that sturgeon growth and development are impaired by diminished
levels of dissolved oxygen in water, and that increasing incidence of seasonal oxygen depletion
in Chesapeake Bay waters may degrade sturgeon habitat (Secor and Gunderson 1998)5.

Consistent with the findings of this study, and pursuant to Endangered Species Act provisions,
EPA is required to use its authority to further the purpose of protecting threatened and
endangered species (See 16 U.S.C. § 1536(a)). Therefore, any Chesapeake Bay specific
dissolved oxygen criteria published by EPA and any resultant dissolved oxygen water quality
standard promulgated by Bay states for applications to the Chesapeake Bay and/or tidal
tributaries must be fully protective of shortnose sturgeon.

5 Secor, D.H. and T.E. Gunderson. 1998. Effects of hypoxia and temperature on survival,
growth, and respiration of juvenile Atlantic stuigeon, Acipenser oxyrinchus. Fishery Bulletin
96:603-613

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WORKING DRAFT No. 1	July 3, 2001

Table B-l. Endangered Species in Maryland, Delaware, Virginia, and the District of Columbia.
Source : FWS website (http://ecos.fws.gov/webpage/webpage usa lists.html? )

Listings by State and Territory, as of 10/12/2000
Notes:

Displays one record per listing entity.

Includes experimental populations and similarity of appearance species.

Pertains to the range of a species, not the listing status within a State/Territory.

Includes non-nesting sea turtles and whales in State/Territory coastal waters.

Includes species under the sole jurisdiction of the National Marine Fisheries Service.

Maryland — 26 listings

Animals —19

Status Listing

E	Bat, Indiana (Myotis sodalis)

E	Darter, Maryland (Etheostoma sellare)

T	Eagle, bald (lower 48 States) (Haliaeetus leucocephalus)

T	Plover, piping (except Great Lakes watershed) (Charadrius melodus)

E	Puma, eastern (Puma concolor couguar)

T	Sea turtle, green (except where endangered) (Chelonia mydas)

E	Sea turtle, hawksbill (Eretmochelys imbricata)

E	Sea turtle, Kemp's ridley (Lepidochelys kempii)

E	Sea turtle, leatherback (Dermochelys coriacea)

T	Sea turtle, loggerhead (Caretta caretta)

E	Squirrel, Delmarva Peninsula fox (except Sussex Co., DE) (Sciurus niger cinereus)

E	Sturgeon, shortnose (Acipenser brevirostrum)

T	Tiger beetle, northeastern beach (Cicindela dorsalis dorsalis)

T	Tiger beetle, Puritan (Cicindela puritana)

T	Turtle, bog (northern) (Clemmys muhlenbergii)

E	Wedgemussel, dwarf (Alasmidonta heterodon)

E	Whale, finback (Balaenoptera physalus)

E	Whale, humpback (Megaptera novaeangliae)

E	Whale, right (Balaena glacialis)

Plants — 7
Status Listing

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T	Joint-vetch, sensitive (Aeschynomene virginica)

E	Gerardia, sandplain (Agalinis acuta)

T	Amaranth, seabeach (Amaranthus pumilus)

T	Pink, swamp (Helonias bullata)

E	Dropwort, Cariby's (Oxypolis canbyi)

E	Harperella (Ptilimnium nodosum)

E	Bulrush, Northeastern (Scirpus ancistrochaetus)

Virginia — 63 listings

Animals — 50

Status Listing

E	Bat, gray (Myotis grisescens)

E	Bat, Indiana (Myotis sodalis)

E	Bat, Virginia big-eared (Corynorhinus townsendii virginianus)

E	Bean, purple Villosa perpurpurea)

E	Blossom, green (Epioblasma torulosa gubernaculum)

T	Chub, slender (Erimystax cahni)

T	Chub, spotfin Entire (Cyprinella monacha)

E	Combshell, Cumberlandian (Epioblasma brevidens)

E	Darter, duskytail Entire (Etheostoma percnurum)

T	Eagle, bald (lower 48 States) (Haliaeetus leucocephalus)

E	Fanshell (Cyprogenia stegaria)

E	Isopod, Lee County cave (Lirceus usdagalun)

T	Isopod, Madison Cave (Antrolana lira)

E	Logperch, Roanoke (Percina rex)

XN	Madtom, yellowfin [XN] (Noturus flavipinnis)

T	Madtom, yellowfin (except where XN) (Noturus flavipinnis)

E	Monkeyface, Appalachian (Quadrula sparsa)

E	Monkeyface, Cumberland (Quadrula intermedia)

E	Mucket, pink (Lampsilis abrupta)

E	Mussel, oyster (Epioblasma capsaeformis)

E	Pearlymussel, birdwing (Conradilla caelata)

E	Pearlymussel, cracking (Hemistena lata)

E	Pearlymussel, dromedary (Dromus dromas)

E	Pearlymussel, littlewing (Pegias fabula)

E	Pigtoe, finerayed (Fusconaia cuneolus)

E	Pigtoe, rough (Pleurobema plenum)

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E	Pigtoe, shiny (Fusconaia cor)

T	Plover, piping (except Great Lakes watershed) (Charadrius melodus)

E	Puma, eastern (Puma concolor couguar)

E	Rabbitsfoot, rough (Quadrula cylindrica strigillata)

E	Riffleshell, tan (Epioblasma florentina walkeri)

E	Salamander, Shenandoah (Plethodon shenandoah)

T	Sea turtle, green (except where endangered) (Chelonia mydas)

E	Sea turtle, hawksbill (Eretmochelys imbricata)

E	Sea turtle, Kemp's ridley (Lepidochelys kempii)

E	Sea turtle, leatherback (Dermochelys coriacea)

T	Sea turtle, loggerhead (Caretta caretta)

E	Snail, Virginia fringed mountain (Polygyriscus virginianus)

E	Spinymussel, James (Pleurobema collina)

E	Squirrel, Delmarva Peninsula fox (except Sussex Co., DE) (Sciurus niger cinereus)

E	Squirrel, Virginia northern flying (Glaucomys sabrinus fuscus)

E	Sturgeon, shortnose (Acipenser brevirostrum)

E	Tern, roseate (northeast U.S. nesting pop.) (Sterna dougallii dougallii)

T	Tiger beetle, northeastern beach (Cicindela dorsalis dorsalis)

T(S/A) Turtle, bog (southern) (Clemmys muhlenbergii)

E	Wedgemussel, dwarf (Alasmidonta heterodon)

E	Whale, finback (Balaenoptera physalus)

E	Whale, humpback (Megaptera novaeangliae)

E	Whale, right (Balaena glacialis)

E	Woodpecker, red-cockaded (Picoides borealis)

Plants —13

Status Listing

T	Joint-vetch, sensitive (Aeschynomene virginica)

E	Rock-cress, shale barren (Arabis serotina)

T	Birch, Virginia round-leaf (Betula uber)

E	Bittercress, small-anthered (Cardamine micranthera)

E	Coneflower, smooth (Echinacea laevigata)

T	Sneezeweed, Virginia (Helenium virginicum)

T	Pink, swamp (Helonias bullata)

E	Mallow, Peter's Mountain (Iliamna corei)

T	Pogonia, small whorled (Isotria medeoloides)

T	Orchid, eastern prairie fringed (Platanthera leucophaea)

E	Sumac, Michaux's (Rhus michauxii)

E	Bulrush, Northeastern (Scirpus ancistrochaetus)

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T Spiraea, Virginia (Spiraea virginiana)

District of Columbia — 3 listings
Animals — 3
Status Listing

E Amphipod, Hay's Spring (Stygobromus hayi)
T Eagle, bald (lower 48 States) (Haliaeetus leucocephalus)
E Puma, eastern (Puma concolor couguar)

Plants — 0

Delaware —19 listings
Animals —15
Status Listing

T	Eagle, bald (lower 48 States) (Haliaeetus leucocephalus)

T	Plover, piping (except Great Lakes watershed) (Charadrius melodus)

E	Puma, eastern (Puma concolor couguar)

T	Sea turtle, green (except where endangered) (Chelonia mydas)

E	Sea turtle, hawksbill (Eretmochelys imbricata)

E	Sea turtle, Kemp's ridley (Lepidochelys kempii)

E	Sea turtle, leatherback (Dermochelys coriacea)

T	Sea turtle, loggerhead (Caretta caretta)

E	Squirrel, Delmarva Peninsula fox (except Sussex Co., DE) (Sciurus niger cinereus)

XN	Squirrel, Delmarva Peninsula fox [XN] (Sciurus niger cinereus)

E	Sturgeon, shortnose (Acipenser brevirostrum)

T	Turtle, bog (northern) (Clemmys muhlenbergii)

E	Whale, finback (Balaenoptera physalus)

E	Whale, humpback (Megaptera novaeangliae)

E	Whale, right (Balaena glacialis)

Plants — 4

Status Listing

T	Pink, swamp (Helonias bullata)

T	Pogonia, small whorled (Isotriamedeoloides)

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E Dropwort, Cariby's (Oxypolis canbyi)

T Beaked-rush, Knieskern's (Rhynchospora knieskernii)

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Table B-2. Endangered species in Chesapeake Bay tidal waters.

T	Sea turtle, green (except where endangered) (Chelonia mydas)

E	Sea turtle, hawksbill (Eretmochelys imbricata)

E	Sea turtle, Kemp's ridley (Lepidochelys kempii)

E	Sea turtle, leatherback (Dermochelys coriacea)

T	Sea turtle, loggerhead (Caretta caretta)

E	Whale, finback (Balaenoptera physalus)

E	Whale, humpback (Megaptera novaeangliae)

E	Whale, right (Balaena glacialis)

E	Sturgeon, shortnose (Acipenser brevirostrum)

Sources:

Personal communication, Jacqueline Johnson, Chesapeake Bay Program Offfice/Interstate
Commission on the Potomac River Basin

U.S. Environmental Protection Agency.1998. A Comprehensive List of Chesapeake Bay Basin
Species 1998. EPA 903R-98-013. Chesapeake Bay Program. Annapolis, MD.

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