Eutrophication is the overabundance of nutrients in a body of water that results in harmful algal blooms, which can lead to depletion of dissolved oxygen and loss of fish and seagrass. Shellfish (e.g., oysters, clams, mussels) filter nutrients from the water, and thus have the potential to improve water quality. Given the nutrient removal ability of shellfish, we are estimating the value of ecosystem services maintained or enhanced in the Potomac River estuary via oyster aquaculture.
Why We Care
Nutrients degrade water quality and decrease habitat for fish and other estuarine organisms, including commercial and recreational fisheries. Our research supports development of local Chesapeake Bay nutrient water quality trading programs and water quality management programs, and will provide an approach for broader application nationally. Additionally, expansion of shellfish aquaculture could stimulate seafood production and create jobs.
What We Did
This NOAA–USGS study used a modeling approach to examine how activities in the watershed affect the estuary's water quality. The research team evaluated nitrogen flows from the Potomac River headwaters and used the Assessment of Estuarine Trophic Status (ASSETS) model to evaluate the nutrient-related water quality conditions of the estuary. The team used the Farm Aquaculture Resource Management (FARM) model to estimate the amount of nitrogen removed, the potential economic benefit of the water cleaning service provided by the shellfish, and the credit potential for trading nitrogen in a nutrient trading program. The FARM model also determines changes in chlorophyll and dissolved oxygen related to aquaculture that can be used to evaluate the impact of the farm on local eutrophication status.
What We Found
Oyster aquaculture in the Potomac River estuary could result in significant improvements to water quality. All of the nitrogen currently polluting the Potomac River estuary could be removed if 40 percent of the river bed were used for shellfish cultivation. It was determined that a combination of aquaculture and restored oyster reefs may provide even larger overall ecosystem benefits. Oysters, which feed by filtering, can clean an enormous volume of water of algae that can cause poor water quality. Oyster aquaculture, together with traditional nutrient management measures, could improve water quality.
This research approach will be used in other estuaries to inform the decision regarding the use of oysters and other bivalve shellfish as a Best Management Practice (BMP) for nutrient management. The approach can be used in other coastal waterbodies in the U.S. and globally that support bivalve shellfish aquaculture. Additionally, the results of this work will inform the discussion and decision of whether to include shellfish growers in nutrient credit trading programs being developed in coastal areas in the U.S. and elsewhere.