Award: OCE-1737170

The goal of this project was to investigate differences among oyster populations in the northern Gulf of Mexico. We compared whole genome sequences of oysters across eight populations in Louisiana and Texas, and we tested for differences in heat, salinity and low oxygen stress tolerance for four populations. Oysters from these populations inhabit very different environments, with oysters from Louisiana experiencing lower salinity than oysters from Texas. Low salinity can be extremely stressful for oysters, and we expected that oysters from Louisiana would be better adapted to this stressor. However, we found that most oyster populations in our study had relatively similar tolerance to low salinity. Only populations from southern Texas were different from the others, with lower tolerance of salinity stress and greater tolerance of low oxygen stress. These observations are consistent with our genomic sequencing results: most of the oyster populations in in our study had similar genomes, with the exception of those from southern Texas, which were somewhat differentiated. Our results have important implications for oyster management in this region. We had hoped that we would be able to identify populations with especially high tolerance of low salinity. This would allow managers to use these oysters as brood stock for restoration efforts aimed at re-populating oyster reefs after low salinity-induced mortality events. The fact that we observed relatively few differences in salinity tolerance across most of the populations used in our study suggests that restoration focused on low salinity tolerant oysters may not be a viable management strategy. Last Modified: 05/07/2022 Submitted by: Morgan Kelly