The overarching goal of this region-based work is to protect the living resources of the Chesapeake Bay and its tributaries. EPA has identified five habitats—or designated uses—that affect the majority of aquatic life in the bay for the purpose of refining criteria development:
- The migratory fish spawning and nursery designated use protects migratory and resident tidal freshwater fish during the late winter-to-late spring spawning and nursery season in tidal freshwater-to-low-salinity habitats.
- The shallow-water bay grass designated use protects underwater bay grasses and the many fish and crab species that depend on the vegetated shallow-water habitat.
- The open-water fish and shellfish designated use focuses on surface water habitats in tidal creeks, rivers, embayments, and the mainstem Chesapeake Bay.
- The deep-water seasonal fish and shellfish designated use protects animals inhabiting the deeper transitional water-column and bottom habitats between the well-mixed surface waters and the very deep channels.
- The deep-channel seasonal refuge designated use protects sediment-dwelling worms and small clams that bottom-feeding fish and crabs consume.
Ecological conditions and associated values were identified for each of the habitats/designated uses along with an assessment of their sensitivity to nutrients, DO, water clarity, and chlorophyll a. For example, the shallow-water bay grass habitat was determined to have value for protecting fish and crab species when healthy. Excessive nutrient inputs can trigger increases in algal production and associated reductions of light availability to the detriment of the bay grass, and low DO can harm the bottom-dwelling biota. Management goals and criteria were specifically derived to protect species and communities in those habitats during specific time periods.
Assessment endpoints were evaluated for ecological relevance and value to management goals for the five Chesapeake Bay habitats/designated uses. DO, water clarity, and chlorophyll a were chosen as endpoints to provide the basis for defining the water quality conditions necessary to protect the five habitats. DO and water clarity are numeric criteria; chlorophyll a is a narrative criterion.
Key relationships between nutrients and the assessment endpoints were defined for the five Chesapeake Bay habitats/designated uses. The relationships were visually represented in conceptual models (USEPA 2003).
Reference:
USEPA. 2003. Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries. EPA 903-R-03-002. U.S. Environmental Protection Agency, Region III, Chesapeake Bay Program Office, Annapolis, Maryland and Region III, Water Protection Division, Philadelphia, Pennsylvania in coordination with Office of Water, Office of Science and Technology, Washington, D.C. Accessed October 2016. https://www.chesapeakebay.net/content/publications/cbp_13142.pdf Exit.