Ongoing global environmental changes pose an unprecedented threat to global biodiversity; in particular increasing environmental temperatures and decreasing ocean pH (Ocean Acidification or OA, as a result of increased seawater pCO2−). The extent to which these two drivers will act synergistically, reducing the thermal tolerance window of individual species, and so potentially affect their large-scale distribution, is only beginning to be understood. Here we present a formal test on the potential synergistic effect of elevated temperatures and hypercapnic sea water on the rate of O2 uptake (as a proxy for metabolism), tolerance to heat, and the degree of exoskeleton calcification in the intertidal porcellanid crab Porcellana platycheles. Eighty individuals crabs were haphazardly assigned to one of four treatments, and kept for 40 days at either 15.0 °C (seasonal ambient) or 20.0 °C (+ 5 °C), and at either pH 8.0 (seasonal ambient) or 7.4. In Porcellana platycheles metabolic activity and tolerance to heat were positively affected by increasing temperature, whilst the degree of exoskeleton calcification was negatively affected. No effect of pH was detectable. It is therefore suggested that P. platycheles may not be affected by medium-term exposure to the predicted level of OA, but that acclimation to elevated temperatures may result in improved tolerance of high temperatures despite an increase in metabolic costs and a decrease of calcification. Our results are discussed within a broader ecological and evolutionary context, with particular emphasis on the idea that intertidal species may be to some extent exapted to hypercapnic exposure.
Calosi, P., Donohue, P., Alber, S., and Spicer, J. I., 2009. Synergistic effect of ocean acidification and elevated temperature on the physiological ecology of the intertidal crab Porcellana platycheles. Comparative Biochemistry and Physiology – Part A: Molecular & Integrative Physiology 153(2):169. Abstracts of the Annual Main Meeting of the Society of Experimental Biology, 28th June – 1st July, Glasgow, UK. Abstract.