| Summary: | The Arctic is experiencing accelerated warming. Increasing temperature is known to affect species distribution and abundance but knowledge about the impacts on Arctic marine biogeography remains limited. Blue mussels (genus Mytilus) constitute a key ecological role in the littoral zone, and they are expected to be sensitive to climate changes. To study this, we used a time-for-space approach along a latitudinal climate gradient from the subarctic to High Arctic in West Greenland. We studied abundance, growth patterns and age structure at 73 sites located at five locations ranging from 64 to 77°N, as well as the variation in cold tolerance between seasons and latitudes. Abundance declined >95% with increasing latitude from an average of 23.67 to 0.71 individuals 0.0625 m-2 from Nuuk to Upernavik at the mid-intertidal level. Sub-zero air temperatures and exposure time was of central importance for the distribution in Greenland forcing mussels to find refuge in microhabitats, such as crevices and macroalgae in the lower part of the intertidal. Adult blue mussels were able to significantly adjust their cold tolerance by up to 1°C on both on seasonal and latitudinal scales. Despite a latitudinal decline in the observed maximum individual age, the estimated annual mortality rates of adults showed little variation between localities. However, the abundance 1-year-old recruits significantly declined with latitude, indicating that the observed geographical patterns in abundance are controlled at the earliest life-stages. Thus, blue mussels abundance and age structure can be regarded as a sensitive first indicator for climate impacts in the Arctic as physiological plasticity did not confound patterns. In conclusion, if air temperatures continue to increase, blue mussels may increase their abundance and vertical distribution in the intertidal Greenland. Because blue mussels are key species future changes in distribution may have wide-ranging effects on the intertidal community in Greenland.
|
|---|