R/AQ-5a

Strategic focus area:

Description:

OBJECTIVES : Our primary objective is to assess off-bottom oyster and mussel aquaculture effects on surrounding sediments and nutrient regeneration processes. We seek to generate data and refine models to quantify the effects of bivalve aquaculture on the surrounding ecosystem, and to develop design guidelines to help mitigate any possible adverse effects. We will carry out our first year studies and model development at a shallow oyster aquaculture site in Chesapeake Bay, and will repeat our studies to validate the modeling approaches at a deeper mussel aquaculture site in coastal Maine in the second year. We will present our results and recommendations to coastal zone managers, and will help them learn to use these tools for guidance in locating farms in the coastal zone. We will also make our results, recommendations, and tools available to aquaculturists for optimizing bivalve stocking density, thereby helping minimize some of the adverse effects stemming from over enrichment of sediments by shellfish fecal waste. METHODOLOGY: We will work in cooperation with Marinetics oyster aquaculture farm in Chesapeake Bay, and Pemaquid Mussel Farms, a mussel farm in Maine. In Year 1 at the Marinetics site we will quantify deposition, resuspension, and dispersal of feces and pseudofeces and changes in sediment characteristics, including inorganic nutrient release and organic carbon accumulation. We will use these data to obtain a quantitative understanding of the relationships between dispersal and breakdown of particulate waste generated from shellfish aquaculture relative to the physical and sedimentological characteristics of a site and linked to seasonal variability in oyster feeding. We will integrate information on these effects, relative to the physical and sedimentological characteristics of a site, into Shellfish-DEPOMOD, and will explore several refinements of the model based on the data and our modeling experience. We will also model changes in sediment biogeochemistry associated with deposition of the particulate waste along the dispersal plume. In Year 2 we will measure the same processes at the deeper mussel aquaculture site in Maine and compare these results to predictions from our model. This will test the predicative capability of our model validation and allow us to make any necessary adjustments. Finally, we will develop a series of semi-empirical guidelines for optimizing siting of bivalve aquaculture leases within the coastal zone in a manner that minimizes adverse effects and possibly enhances benthic denitrification. RATIONALE: A major impediment to the expansion of shellfish culture is the often considerable opposition to the use of public waters due to perceived adverse environmental consequences. Until there is a better understanding of the interaction between aquaculture and the surrounding environment it will continue to be difficult to obtain the necessary permits to culture shellfish in coastal and estuarine locations in the USA. In addition, knowledge of aquaculture/environment interactions will lead to sustainable production practices which may be marketed as part of the trend towards sustainable means of food production. Development of shellfish farms is an important way to help sustain traditional lifestyles and provide jobs and incomes to coastal communities, maintaining a working waterfront where declining wild stocks of fish and shellfish are causing reduced harvest and leading to severe economic hardship. Our research addresses the Sea Grant program priority area of "smart design" methods for bivalve aquaculture and also addresses the priority of developing a planning tool to allow aquaculture farms to be located optimally in the coastal zone in a manner consistent with ecosystem-based management.