A Freshwater Inflow Model for the Conservation of Texas Oyster Reefs

Abstract

Long-term changes in freshwater inflows over a climatic gradient along the Texas coast have provided an opportunity to examine relationships between inflows and oyster dynamics; specifically, the oysters’ relationship with the oyster parasite Perkinsus marinus. The eastern oyster (Crassostrea virginica) is used in this study as a bioindicator to identify the environmental conditions needed to regulate P. marinus on a regional scale and a local scale. On a regional scale, 15+ years of oyster disease, climate indices, freshwater inflow, and salinity data from 6 Texas estuaries have been compiled to determine freshwater needs across a climatic gradient, and to link climate variability to salinity regimes and oyster disease dynamics. This study found that P. marinus is an effective bioindicator and accessible way to manage freshwater inflow to Texas Estuaries. Climatic conditions played a strong role in governing estuarine salinity patterns and P. marinus disease dynamics among Texas estuaries. Climate-driven wet conditions across Texas estuaries promote significantly lower proportions of oysters infected with P. marinus and less severe infections. At the local scale, there was a spatial gradient of salinity and P. marinus infections, moving from reefs closest to the freshwater inflow source to reefs closest to the Gulf inlet. This study found climate variability affected salinity, which affected P. marinus infections. Results from this study were used to help support multi-year adaptive management plans that account for climate patterns expressed in multiyear periodicities.