Metabolic cold adaptation and aerobic performance of blue mussels (Mytilus edulis) along a temperature gradient into the High Arctic region

The blue mussel (Mytilus edulis) has recently expanded its northern distribution in the Arctic and is therefore considered to be a sensitive indicator of climate changes in this region. In this study, we compared aerobic performance of blue mussels from High Arctic, Subarctic and temperate populations at different temperatures. Standard metabolic rates (SMR) and active metabolic rates (AMR) were measured for each population, and absolute (AMR - SMR) and factorial () scopes were calculated. Blue mussels from the temperate population had the lowest Q(10) (= 1.8) and the largest thermal window (-1 to 25 A degrees C), whereas Q(10) values in the Arctic populations were 1.9 (Subarctic) and 2.3 (High Arctic), with a thermal window of -1 to 21 A degrees C. Aerobic scope increased with rising temperatures, reaching a maximum at 14 A degrees C (temperate) and 7 A degrees C (Subarctic and High Arctic, respectively), after which a decrease was observed at temperatures exceeding 14 A degrees C. At low temperatures (-1 A degrees C), the average SMR of the High Arctic population was 93 % higher than that of the temperate population and 22 % higher than that of the Subarctic population. Combined, our results demonstrate physiological adaptation and plasticity of blue mussels across latitudes spanning from 56 to 77A(0)N. This indicates that low ocean temperature per se does not constrain metabolic activity of Mytilus in the Arctic; rather, we speculate that maturation of reproductive tissues, larval supply and annual energy budgets are the most relevant factors influencing Mytilus populations near their northern distributional edge in the Arctic.