Physiological response of the blue mussel Mytilus edulis to differences in food and temperature in the Gulf of Maine

Studies performed in the Gulf of Maine (GOM) during the spring of 2006 examined populations of the blue mussel, Mytilus edulis at several intertidal locations. Several parameters were measured including maximum length, diet (stable isotope composition), and the physiological performance of individual mussels using condition indices and RNA/DNA ratios. These same mussels were also assessed for their response to differences in seawater temperature by quantifying the expression of heat shock proteins (HSP70) and the activities of the antioxidant enzyme, superoxide dismutase (SOD). These data were then interpreted in the context of sea surface and air temperatures as well as chlorophyll a concentration and the genetic structure of mussel populations. Populations of M. edulis throughout the GOM were found to be genetically homogenous and consumed a mixed diet of phytoplankton and detritus. Mussels exposed to higher seawater temperatures also showed a significant increase in the expression of HSP70 and activities of SOD. The site-specific interplay between the amount of energy gained from the available food resources and the costs associated with protection against the effects of elevated seawater temperatures shows that these mussels exhibit phenotypic plasticity at different sites which could play an important role in the population dynamics of this key member of the rocky intertidal.