https://phys.org/news/2018-10-climate-threat-tolerant-oysters.html

All organisms, including oysters, show higher expressions of genes that are involved with DNA damage and protein unfolding in response to extreme stress. Protein unfolding is a process in which proteins lose their structure and become unstable, which, if not repaired, will eventually lead to the animal's death. Researchers study the Olympia oyster because they are a "foundation species," meaning the presence of oysters provides habitat for a large number of other smaller species and creates a much healthier ecosystem. If the oysters die out, all of the associated species will too. Because of the vital role oysters play in coastal ecosystems, researchers want to know if oysters living in certain areas are more tolerant of low salinity and therefore better equipped to survive climate change.

The research team exposed all three groups of oysters and their offspring to low-salinity seawater (around 0.5 percent salt) and measured their gene expression patterns. They found that the oysters living closest to the large estuary were more tolerant of a five-day exposure to low-salinity seawater. "More frequent exposure to freshwater in this region likely forced oysters to evolve new ways of surviving in low salinity," explained Tyler Evans, Ph.D., from California State University East Bay, and first author of the study.