| Summary: | Intertidal zone organisms experience daily fluctuations in temperature and pH, and these fluctuations are expected to increase along the California coast under climate change scenarios. How intertidal organisms respond to environmental variability of temperature and pCOi is largely unknown. There is an urgent need for lab studies to examine if and how incorporating natural environmental variability and anthropogenic changes in the environment together will affect marine organisms. I investigated performance of the porcelain crab, Petrolisthes cinctipes, under intertidal zone conditions with variation in temperature and pCOi. Adult P. cinctipes were exposed to three temperature spikes (11°C, 25°C or 30°C) during a simulated daytime low tide, or were not immersed or heated. At night the crabs in each treatment were exposed to constant pH (8.1) or to pH spikes to 7.6, or 7.15. Following two weeks of acclimation, we measured respiration rates at 11 and 18°C and upper thermal limits of cardiac performance (CTmax ). Metabolic depression was observed in crabs that experienced daily aerial heat spikes, and the depression was stronger in low pH acclimated individuals. CTmax was elevated with acclimation temperature, and the elevation was higher under low pH acclimation. Our results indicate that there are negative interactive effects of pH and temperature variability on the metabolism and negative interactive effects of pH and temperature variability on thermal limits of these intertidal zone crabs.
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