Pan-Svalbard Assessment of Climate Forcing and Ecosystem Variation: Decadal-scale Evidence from Bivalve Growth Rates

Understanding the consequences of climatic change in the Arctic requires linking ecosystem responses to both natural and anthropogenic climatic variations, over a range of temporal and spatial scales. Growth histories and geochemical information contained in the shells of Arctic bivalves provide continuous records of physical and biological information over lifetimes spanning decades to centuries. We examined growth rates and interannual gowth patterns from 223 individuals of the circumpolar Greenland Cockle (Serripes groenlandicus) from 11 sites around the Svalbard archipelago. Environmental conditions at these sites spanned a range of oceanographic and environmental gradients, from strongly Atlantic-influenced on the west coast to high-Arctic in northeast Svalbard. Absolute growth was up to 3 times greater at heavily Atlantic-influenced locations compared to the most Arctic-influenced areas. Standardized growth indices exhibited interannual patterns with some common features, including a marked shift from relatively greater to poorer growth in the mid-1990s. This shift was consistent with phase-shifts in large-scale climatic drivers. Interannual patterns in growth rates were also related to regional manifestations of the large-scale drivers, including atmospheric pressure, precipitation, and sea ice. Notably, we highlight a long-term relationship at some stations between the intensity of the Atlantic water stream (the West Spitsbergen Current) west of Svalbard. Site-to-site variability in the precise relationships between growth and environmental variability indicate that effects on growth are determined by the interaction between large-scale climate drivers and local environmental parameters, and through the regulation and food availability on a local scale. These results demonstrate that sclerochronological proxies can be useful retrospective analytical tools for establishing baselines of ecosystem variability in assessing potential impacts of climatic change on Arctic marine ecosystems.