Poor acclimation capacities in Antarctic marine ectotherms

Animals can respond to temperature change by the following means: using physiological flexibility (including acclimation); or adapting; or migrating, with acclimation proposed as the major mechanism dictating prospects for survival in marine groups. In this study, 6 species of Antarctic invertebrate covering 4 phyla, Echinodermata, Mollusca, Brachiopoda and Crustacea were subjected to acclimation trials at 3A degrees C for 60 days. Using acute upper lethal temperatures as a metric of ability to acclimate, only one species (Marseniopsis mollis) increased its acute upper limit. Furthermore, analysis of oxygen consumption on the urchin Sterechinus neumayeri and the amphipod Paraceradocus gibber showed their metabolic rates were also not compensated over the 60-day exposure period. Thus, 5 out of 6 species failed to acclimate to temperatures only 3.5A degrees C above the annual average and 1-2A degrees C above current summer maximum values. We discuss the proposal that the abilities of Antarctic marine species to adjust to elevated environmental temperatures are as limited, if not more so, than tropical species.