Nutrient regeneration by the zebra mussel (Dreissena polymorpha)

Changes in suspended seston and soluble nutrients were examined as a function of zebra mussel (Dreissena polymorpha) density in flow-through sediment-water microcosms to determine impacts on nutrient recycling. Overall, zebra mussels removed >70% of the suspended seston and >80% of the total chlorophyll a input to the microcosms. Declines in organic nitrogen in microcosms were accompanied by density-dependent increases in nitrate-nitrite nitrogen. We suggest that micro nora associated with the sediments in the microcosms were transforming ammonium nitrogen, which is an excretory product of zebra mussels, into nitrate nitrogen. Declines in total phosphorus in the microcosms also coincided with density-dependent increases in the concentration of soluble reactive phosphorus and its rate of regeneration, suggesting enhanced nutrient cycling via excretion. Calculated rates of soluble phosphorus regeneration due to zebra mussel activity ranged from 0.3 to 2.5 mg m(-2) d(-1) at mussel densities ranging between 170 to 1300 individuals m(-2) phosphorus regeneration by zebra mussels could have important implications for the phosphorus economy of many lakes and rivers which have been invaded by this organism.