Chesapeake Bay Nutrient/Sediment Enrichment Criteria
Summary of Status, Draft Criteria, Issues and Next Steps
Dissolved Oxygen
Status
The criteria team has agreed on the application of the EPA Virginian Province marine
dissolved oxygen criteria methodologies and underlying effects data base for derivation of
Chesapeake Bay specific dissolved oxygen criteria.
-	Efforts are underway to supplement the EPA criteria effects data base with data for additional
Bay species, life stages (e.g., juveniles), and effects (e.g., behavioral) and more Bay related
recruitment effects model parameter values supporting derivation of a set of Bay specific
criteria.
Draft Criteria
-	Bay specific criteria will be derived for each of the five designated uses, with the same
criteria values likely to be applied to shallow and open water designated uses.
-	For the shallow water, open water, and deep water designated uses, the criteria will likely be
expressed as a curve (dissolved oxygen vs. time in days) denoting the amount of time
dissolved oxygen concentrations can fall below a longer term (30 day) concentration value
(e.g., 5 mg/L).
-	For migratory spawning/nursery and deep channel designated uses, the criteria will likely be
stated as a concentration not to go below within a specified averaging period.
Issues
-	How to address routine occurrence of anoxic conditions within the deep channel use habitat
when the criteria may be stated as >1 mg/L.
-	Exactly how to set the deep water designated use criteria by adhering to the EPA
methodology yet reflecting the reality of lower dissolved oxygen conditions below the
pycnocline and the needs of the species that inhabit these lower oxygen level habitats.
Next Steps
-	Follow through on compiling the Bay species/life stage/effect data identified by the criteria
team and finalizing changes to the recruitment model parameter values to reflect Bay specific
conditions.
-	Run the above compiled data and revised parameter values through the EPA recruitment
effects model and generate of a series of supplemental species effects curves.
-	Derive a set of Bay specific criteria tailored to the designated uses.
-	Document all the work going into derivation of the Bay criteria.
-	Flesh out the details of the implementation guidance.

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Chlorophyll a
Status
The criteria team has laid out the following elements of a matrix of both quantitative and
collaborative lines of evidence that will form the basis for the Bay specific chlorophyll a
criteria through application of a set of decision rules:
-	Historical concentrations by salinity regime across spring, summer, and annual periods;
-	Ecosystem trophic status synthesized from the worldwide literature;
-	Direction contribution to water column light attenuation;
Contribution to low dissolved oxygen conditions; and
-	Food quality for higher trophic levels.
-	Work is underway in compiling the data necessary to fill out the above matrix.
Draft Criteria
-	Bay specific criteria will be derived for major salinity regimes over seasonal averaging
periods (spring, summer) for application to the migratory spawning/nursery, shallow water
and open water designated uses.
Issues
The exact nature of the decision rules.
The degree of emphasis on quantitative vs. collaborative lines of evidence for criteria
derivation.
-	Resolving some team members concerns about the chlorophyll-dissolved oxygen line of
evidence.
Addressing concerns raised that attainment of the chlorophyll a criteria may drive nutrient
reduction actions beyond those needed to attain the Bay dissolved oxygen and water clarity
criteria.
-	Resolving the details of the criteria implementation procedures-measurement within the
water column, temporal/spatial averaging for defining chlorophyll a criteria attainment.
-	How to address elevated chlorophyll a concentrations above the criteria values due to poorly
flushed tidal systems.
Next Steps
Complete the job of compiling the necessary data and filling out the matrix.
-	Draft up and get team sign-off on the decision rules.
Apply the decision rules to the matrix and lay out the recommended Bay criteria.
-	Document all the work going into derivation of the Bay criteria.
-	Flesh out the details of the implementation guidance.

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Water Clarity
Status
The criteria team has agreed on the water clarity criteria values and is currently focused on
developing recommendations for the depths for application of the criteria values.
A matrix with the following elements is being compiled as the technical basis for
determining the application depths for the criteria:
-	Maximum depth of composite 1971-1999 SAV beds;
-	Maximum restoration depth meeting the minimum light requirements calculated from
1970s-1999 WQ monitoring data;
-	Estimated living resource-based SAV bed depth needs; and
-	Bay water quality model scenario simulated depths meeting the minimum light
requirements (using a range of scenarios).
Draft Criteria
-	Bay specific criteria will be the minimum light requirements developed through the SAV
Technical Synthesis II process derived for the four major salinity regimes over SAV growing
seasons for application to the shallow water and open water designated uses.
Issues
-	Finalizing the depths for application of the water clarity criteria.
-	Determining exactly how the water clarity criteria will be applied to the open water
designated use habitats.
Next Steps
Complete the job of compiling the necessary data and filling out the matrix.
-	Determine recommended application depths first by CBP segment then moving toward wider
salinity regime-based depths.
-	Document all the work going into derivation of the Bay criteria.
-	Flesh out the details of the implementation guidance.

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