| Summary: | Climate change is predicted to facilitate a northward expansion of temperate species into the Arctic. In Greenland, the north-south orientation of the West Greenland coast provides an ideal opportunity to study the impact of climate change on marine species population dynamics and distributions. The blue mussel (Mytilus edulis) has recently expanded its northern distribution in Greenland and is considered to be a sensitive indicator of climate changes. Blue mussels could be a species that would respond to a warmer climate by increased abundance and growth rates in the Arctic. However, adequate data on current distribution and physiological performance of blue mussels in the Arctic is lacking, and knowledge of how “climate” in a broad sense specifically influence population dynamics of this species is unknown. Here, we present data on abundance, age and mortality of blue mussels in West Greenland. We supplement our data with physiological measurements on freezing tolerance and aerobic metabolic performance of intertidal specimens. We hereby attempt to identify links between temperature and physiology and how this might translate into population dynamics in this region of the Arctic. Results show an overall decline in blue mussel abundance along the coast from south to north Greenland. Physiological adaptation and plasticity of blue mussels was found across latitudes spanning from the temperate to the High Arctic region. Combined our results indicate that low ocean temperature per se does not constrain metabolic activity and distribution 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.
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