Genetic Variation of Crassostrea virginica along a Salinity Gradient

The eastern oyster (Crassostrea virginica) has a central ecological role in intertidal and subtidal marine systems as a foundation species.  Oysters are an important commercial fishery and provide habitat structure for other recreational and commercial fisheries, as well as key ecosystem services.  Oysters have been over-harvested, and efforts to restore oyster reefs are underway.  As part of these efforts, we are assessing the amount and distribution of genetic variation in oyster reefs along a salinity gradient in the Mission-Aransas Estuary.  We hypothesize that oysters found near the river mouth, where the salinity is low, will be genetically different from oysters collected from higher salinities in the bay proper.  Oyster spat may show a salinity preference when settling onto a reef.  Results to be presented are from 140 individuals collected from the Mission-Aransas Estuary system, which maintains a strong and well-documented salinity gradient.  Using five microsatellite markers, we will estimate levels of genetic variation by examining number of alleles per locus as well as observed and expected heterozygosity for the oysters collected along this salinity cline.   Genetic differentiation across the salinity gradient will be estimated using appropriate statistical methods.  This study will provide information that will assist resource managers in conservation, management, and restoration of this species.