By Anna Deck, Research Technician

Anna Deck and Dr. Andrew Chang of SERC counting and measuring native oysters in Mill Valley.

Scientists with the San Francisco Bay National Estuarine Research Reserve recently finished our annual oyster monitoring. When the tide is low and rocks in the intertidal zone are exposed, we are able to count and measure native Olympia oyster at sites throughout San Francisco Bay. Year to year, we will be able to watch how oyster populations change as conditions in the bay change with the climate. At one site in China Camp State Park, NERR scientists and colleagues have seen big fluctuations over the past few years. In previous years, there were extremely high numbers of oysters at China Camp relative to other sites in the bay. In 2011, we watched as all the oysters at China Camp died off… What happened that year that could have caused that? California experienced lots of rain during the 2010-2011 winter, which led to increased freshwater flow into the bay and lower salinity levels in the bay. Oysters cannot withstand long durations of reduced salinity. In years following, even though oyster larvae were present in the water, they did not resettle at China Camp. This past fall that we finally observed oysters reestablishing their population at China Camp! We were glad to see them growing and thriving this spring in our survey, meaning that most of them survived through the winter. As our climate continues to change, precipitation affecting San Francisco Bay is predicted to become more variable with longer dry periods punctuated by more intense and frequent storms. Based on what you just learned about how oysters at China Camp responded to a recent wet year, what do you think might happen to populations there in the future? You can visit to learn more about research by NERR scientists and colleagues related to climate change effects on Olympia oysters.

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