Variable Effects of a Sublethal and Lethal ‘Heat Wave’ on Juvenile Olympia Oysters, Ostrea lurida, previously exposed to Low pH Conditions
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Prevalent upwelling in summer months in the Northwest United States can bring anomalously acidified waters to Puget Sound. This, combined with the effects of increasing summer peak water temperatures, poses a joint threat from two separate abiotic factors directly linked to climate change. We investigated the response in mortality of Olympia Oysters, Ostrea lurida, to these two factors by pretreating oysters in three different pH conditions for different lengths of time before exposing them to a three-day lethal and sublethal heat shock with different day and night temperatures. We were able to determine the lethal and near-sublethal temperature for Olympia oysters in a three-day heat shock as 41°C and 36°C, respectively. When analyzing mortality, our experiment yielded ambiguous statistical results but did indicate that oysters pretreated in low pH conditions may have less mortality in a lethal heat shock than oysters in high pH conditions. This suggests that Olympia oysters could be able to develop resistance to a primary stress after previous exposure to an unrelated secondary stress. We plan to investigate morphological and structural qualities of these oyster shells to determine what additional effects the various pH pretreatments might have had on the oysters.