| Summary: | Intertidal zone organisms naturally experience daily pH fluctuations reaching values at or below predicted ocean acidification (OA) levels. The intertidal zone porcelain crab, Petrolisthes cinctipes, was used to study responses to OA across early life history stages that occur in habitats with different pH characteristics. In these crabs, embryonic development occurs in the intertidal zone, larvae mature in the more stable planktonic pH environment, and at settlement juvenile crabs return to benthic intertidal zone. The aim of this study was to assess the sub-lethal consequences of sustained OA during the potentially vulnerable embryonic, larval and juvenile stages. Our results showed that hatching success did not differ between pH conditions after short-term exposure, but ranged from 30-95% among broods. Larval survival was not affected by nine days exposure to acidification. However, juvenile survival was lower during 40d exposure to low pH. Embryonic and larval heart rates were 37% and 20% lower at low pH, and there was a brood-specific response to low pH in embryos. Embryonic and larval cardiac output were also reduced by 52% and 21% respectively under low pH with little or no modification of stroke volume. Egg size did not change after four days under low pH compared to a 15% increase in ambient conditions. Embryos and larvae of P. cinctipes showed a sub-lethal response to short-term acidification that involves a reduction in cardiac performance with no subsequent effect on hatching success or survival. We conclude that long-term sustained acidification could be detrimental to some organisms despite historical exposure to naturally fluctuating hypercapnic environments.
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