Linking rising pCO2 and temperature to the larval development and physiology of the American lobster (Homarus americanus)

Few studies have evaluated the joint effects of elevated temperature and pCO(2) on marine organisms. In this study we investigated the interactive effects of Intergovernmental Panel on Climate Change predicted temperature and pCO(2) for the end of the 21st century on key aspects of larval development of the American lobster, Homarus americanus, an otherwise well-studied, iconic, and commercially prominent species in the northeastern United States and Atlantic Canada. Our experiments showed that larvae (stages I-III) and postlarvae (stage IV) reared in the high temperature treatments (19 degrees C) experienced significantly lower survival, developed twice as fast, and had significantly higher oxygen consumption rates, than those in ambient treatments (16 degrees C). Larvae from the ambient temperature/high pCO(2) (750 ppm) treatment had significantly longer carapace lengths, greater dry masses in stages I-III and higher C:N ratios in stage IV than larvae from all other treatments. Stage IVs raised in the high pCO(2) treatment at 19 degrees C had significantly higher feeding rates and swimming speeds than stage IVs from the other three treatments. Together these results suggest that projected end-century warming will have greater adverse effects than increased pCO(2) on larval survival, and changing pCO(2) may have a complex effect on larval metabolism and behaviour. Understanding how the most vulnerable life stages of the lobster life cycle respond to climate change is essential in connecting the northward geographic shifts projected by habitat quality models, and the underlying physiological and genetic mechanisms that drive their ecology.