Effects of ocean acidification and warming on growth of juvenile porcelain crabs

Sea surface pH is projected to decline 0.3 - 0.4 units by the year 2100. In the same time span, global surface temperature is expected to increase up to 4°C. Many studies have recently focused on the interactive effects of multiple stressors on the physiology of intertidal organisms, although, the interaction of pH and temperature incorporating the natural variability of those parameters has hardly been addressed, especially in juvenile organisms. The effects of variable pH decrease and temperature increase on rocky intertidal zone adult porcelain crabs, Petrolisthes cinctipes, have been shown to increase thermal tolerance and depress metabolic rate. One interpretation is that energy demand for homeostasis increases while overall energy supply decreases, which may cause energy to be diverted from activity, growth, and/or reproduction. To determine if energy is re-allocated from growth, juvenile P. cinctipes were exposed to pH 8.0 and pH 7.5 seawater during a high tide period and aerial temperatures of 12°C and 24°C during a low tide period. Survival, growth, and metabolic rates were examined after 26 days of exposure. There were no effects of pH and temperature on survival or growth. However, temperature had an effect on metabolic rate, as metabolic rate increased with elevated temperature. These results suggest that juvenile P. cinctipes may be tolerant of future climate change conditions in the rocky intertidal under medium-term pH and temperature exposure.