Eastern Oyster Physiological Responses to Acute and Chronic Exposure to Suspended Sediments

Abstract

Louisiana estuaries provide habitat for some of the most productive population of the eastern oyster, Crassostrea virginica in the Gulf of Mexico. Coastal alterations, including changes in river flow of the Mississippi River, sediment diversions, and climate change, are likely to impact areas supporting oyster production. Although oysters in Louisiana already experience periods of high total suspended sediment, these coastal alterations may increase duration, frequency, and concentration of high suspended sediment concentrations over oyster grounds, which could have significantly impact oyster physiology and production by affecting basic physiological functions of oysters. In this study, we measured effects of acute (1 hour) and chronic (8 weeks) exposure of suspended sediment concentrations on eastern oyster physiology. Specifically, using a series of controlled laboratory experiments, we monitored oyster respiration rate (O2 L-1 hr-1 g-1 dry tissue weight) and clearance rate (L hr-1 g-1 dry tissue weight) in response to acute and chronic exposure to suspended sediment concentrations. Acute exposure at six sediment concentrations (0, 10, 50, 200, 500, 1000 mg L-1) indicated sediment concentration significantly affected oyster clearance rates (p < 0.0001), but not respiration rates (p = 0.12). Chronic exposure at two salinities (6 and 15 ppt) and three sediment concentrations (0, 50, 400 mg L-1) indicated that clearance rates were not significantly affected by sediment concentration or salinity (p = 0.71 and p = 0.86 respectively). Respiration rate was not significantly affected by sediment concentration (p = 0.21) but was significantly affected by salinity (p = 0.0086). Overall, reduced salinity associated with sediment diversions may have greater impacts on oyster growth and survival, particularly if salinities are reduced for extended periods of time. Understanding consequences of high suspended sediment exposure on the eastern oyster is critical to predicting future oyster production potential, impacts from proposed restoration activities, and climate change.