Ecosystem Partners: an Investigation of the nutrient relationship between the filer feeding bivalve Crassostrea virginica and populations of benthic microalgae (2016)

Undergraduate: Abigail Vinson

Faculty Advisor: Mike Piehler
Department: Environmental Science

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This study investigated the effectiveness of benthic microalgae (BMA) as a filter for excess nutrients through two experiments. In the first experiment, nutrient addition by the bivalve Crassostrea virginica was compared to controls in a series of flow-through aquaria, terminating in a tank containing sediment, which was the substrate used for BMA growth. C. virginica increased the ammonium levels of overlying waters by an average of 86.9% in comparison to controls. BMA biomass, measured by chlorophyll a (chl a) concentration, also increased by 38.0% in oyster treatments to a peak concentration of 8.14 mg m-2. Peak chl a concentration was 74.7% higher in C. virginica treatment averages than in controls, providing evidence of stimulated BMA growth due to bivalve nutrient additions. The second experiment compared nutrient attenuation by BMA to two commonly found macroalgae, Codium fragile and Gracilaria tikvaniae. While preliminary tests indicated the possibility for significant nutrient attenuation by both BMA and C. fragile, complications with the experiment produced inconclusive results. Given the current state of knowledge surrounding the interactions across trophic dynamics of oyster reefs, I argue for further studies of the relationship between oysters, BMA, and other inhabitants of oyster reefs. Such research will be imperative for expanding knowledge of trophic interactions and could have broad implications and applications in both natural and cultured settings.