Viability of a Freshwater Mussel (Elliptio complanata) as a Biomechanical Filter for Aquaculture Ponds I: Clearance Rate of Chlorophyll-α

The production and livelihood of aquaculture facilities depend on increased growth of species being harvested. Only 15%-25% of nitrogen and phosphorus are retained in farmed fish even when all feed is consumed. In both marine and freshwater aquaculture systems, bivalves have proven to be an inexpensive method for controlling algal growth through suspension feeding. With 25% of the native U.S. freshwater mussel species under federal protection, their use in aquaculture ponds could lead to further propagation and restoration of natural populations. Elliptio complanata is an important species in Delaware rivers and connected estuaries; a recent two-year study by the United States Geological Survey found that 98% of mussels found in the Delaware River were Elliptio complanata. The objective of this study was to calculate the clearance rate of E. complanata in a laboratory study. This would help us determine if mussels can serve as an addition to chemical and mechanical filtration regiments and thrive in an aquaculture setting. Using feeding chambers we investigated the effect of E. complanata on algae grown from an aquaculture pond and on a cultured alga over a four-hour period. Temperature, dissolved oxygen, and pH were monitored, and samples were than analyzed for total chlorophyll-α. The average of both the single cell using Chlorella vulgaris and mixed assemblage treatments chlorophyll-α clearance rate was 0.187 liters per hour per mussel. Prior to this experiment, these mussels were held for a period for two months in the holding system in the laboratory. The resulting low clearance rate as compared to the previous studies in the field is possibly due to the stress from holding these mussels. However, our study demonstrated that mussels have the potential to be used in an aquaculture setting and/or recreational ponds to help reduce algae populations that can occur as a result of eutrophication.