Greenland cockles (Serripes groenlandicus Mohr 1786) from Bjornoya (Bear Island), Svalbard record environmental change: Local and regional drivers of growth

摘要

Long time series are necessary to separate natural variability from that due to climate change and make it possible to interpret the impact of environmental change on ecosystems. Sclerochrono-logical analysis of environmental records in the shells of mol-lusks make it possible to reconstruct environmental-ecological linkages over sufficiently long time scales to detect ecosystem change. Annually resolved archives can be key indicators of how climate change manifests in the marine ecosystem and are especially important in areas with limited instrumental records. We developed a master growth chronology of the Greenland Cockle (Serripes groenlandicus) from Bear Island (Bjornoya), Svalbard, Norway (74°41'N, 18°56'E) from analysis of annual shell growth increments. The chronology was developed from 13 individuals collected from 80 m deep and ranging in age from 40 to 48 years old (the oldest known individuals of this species to date). The master chronology, expressed as a growth index (GI), extended from 1968 to 2012 and exhibited a cyclical pattern with decadal periods of high growth alternating with slower growth intervals. We identified significant relationships between variations in large-scale climate regimes (e.g. Atlantic Multidecadal Oscillation), local environmental conditions (e.g., sea temperature, sea ice), and shell growth. A model using sea temperature and sea ice explained 34-49% of the annual variations in shell growth patterns. The growth chronology and environmental linkages for cockles at this site in southern Svalbard near the southern extent of Arctic water in the Barents Sea were substantially different than at other locations in Svalbard. We conclude that the Greenland Cockle is quite sensitive to environmental changes over annual to decadal scales and therefore can serve as a proxy of climate change effects on ecosystem processes in the Arctic, but that local environmental processes that regulate food availability to the seabed are key determinants of environmental regulation on shell growth.