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Clark HR, Gobler CJ
Diurnal fluctuations in CO2 and dissolved oxygen concentrations do not provide a refuge from hypoxia and acidification for early-life-stage bivalves
Low dissolved oxygen (DO) and/or low pH conditions occur in productive estuaries both seasonally and diurnally between day and night. Clark & Gobler assessed the effects of constant and diurnally fluctuating acidification and hypoxia on the survival, growth, and development of larval stages of 3 bivalves indigenous to North America. Simultaneous exposure to continuously low pH and DO yielded more negative effects than each factor individually. Diurnal exposure to low pH and/or low DO did not mitigate the negative effects despite significantly higher mean pH and DO levels in these treatments. Hence, diurnal fluctuations of pH and DO did not provide a temporal refuge from hypoxia and acidification for bivalve larvae suggesting that, in an ecosystem setting, such fluctuations can represent a significant environmental threat.