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NCCOS Project

Planning for Sustainable Shellfish Aquaculture in Complex Multiple Use Environments: Determining Social and Ecological Carrying Capacity for South Puget Sound (PECSA)

This project began in September 2012 and was completed in September 2015

Eutrophication is the overabundance of nutrients in a body of water that results in harmful algal blooms, fish kills, and in some cases ecosystem collapse. We are investigating the feasibility of using shellfish to filter out nutrients in the Puget Sound estuary. Using models, field data, and input from stakeholders, we are evaluating aquaculture success, water quality improvement, economic benefits, and the potential credit for carbon and nitrogen trading as a management strategy.

Why We Care
Eutrophication is among the most serious threats to the function and services supported by coastal ecosystems. Attempts to reverse coastal eutrophication have centered on reducing land-based sources of nutrients, such as fertilizer applications and wastewater treatment plant discharges. However, recent studies have shown that removal of nutrients through filtration and growth of shellfish can complement land-based management methods, provide much needed shellfish products (the United States presently imports more than 90 percent of seafood consumed), and create additional jobs and income for aquaculture farmers.

What We Are Doing
NCCOS and partners are using computer modeling to determine the carrying capacity for shellfish aquaculture—and the related potential for nutrient removal—in South Puget Sound. We are using a system-wide ecosystem model, the local scale Farm Aquaculture Resource Management (FARM) model, Assessment of Estuarine Trophic Status (ASSETS) model, and an economic analysis to evaluate the success of aquaculture (growth of shellfish), the impact of the farm on water quality (changes in chlorophyll and dissolved oxygen related to aquaculture

activity), the potential economic benefit of the water cleaning service provided by the shellfish, and the credit potential for trading carbon and nitrogen in a water quality trading program.

Benefits of Our Work
Our team’s methodologies and guidelines will be used to inform marine spatial planning activities locally and throughout the U.S., promoting sustainable shellfish aquaculture and providing a framework for addressing issues that commonly lead to regulatory and permitting conflicts. The removal of phytoplankton and particulate material through filtration by oysters and clams, and the subsequent increase in water clarity allows seagrasses, and thus fish habitat, to reestablish in high turbidity systems. Nutrients are essentially removed from the system when the shellfish are harvested. A farmer can receive credit for the avoided cost of additional water treatment by traditional measures. Our project will both support regional nutrient water quality management programs and provide tools for broader application nationally. Additionally, the project could stimulate seafood production and create jobs through the expansion of aquaculture activities.

Next Steps
We are hoping that the approach used in this study may be used to investigate the potential benefits of shellfish aquaculture in other coastal waterbodies to help improve water quality, increase domestic production of seafood, and increase related jobs.

Additional Resources

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Peer-Reviewed Publications

  • Bricker, S.B., K.C. Rice, O.P. Bricker III. 2014. From Headwaters to Coast: Influence of Human Activities on Water Quality of the Potomac River Estuary. Aquat Geochem 20:291–324.
  • Rose, J.M., S.B. Bricker, J.G. Ferreira. 2015. Modeling shellfish farms to predict harvest-based nitrogen removal. Marine Pollution Bulletin 91:185–190.

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