Abstract
ABSTRACT: Sea ice exerts a strong influence on Arctic marine primary production, thereby influen-cing food availability for secondary producers. Food availability is recognized as one of the primaryconstraints on macrobenthic growth and production. Thus, it may be expected that spatial and tem-poral variability in Arctic sea ice cover influencing primary productivity could translate to the nexttrophic level: the benthic secondary producers. To test whether sea ice cover is coupled to the annualproduction of Arctic benthos, we measured annual growth increments in the shell of the bivalve Clinocardium ciliatum to (1) compare average individual growth rates along a climate gradient fromsub-Arctic to high-Arctic Greenland, and (2) produce time series of inter-annual variation in bivalvegrowth at sites with different sea ice conditions. A significant difference between average individualgrowth rates between the different sites was found. This geographic variation in growth performancewas correlated to the average productive open-water (ice-free) period estimated from sea ice dataobtained from satellites between 1979 and 2003. At locations with low to moderate sea ice cover,growth rates ranged from 80 to 100% of the fastest growing sites. At sites with pronounced sea icecover, bivalve growth was reduced to 35 to 45% of the maximum growth rates. At these 2 sites theyear-to-year variation in bivalve growth correlated negatively with inter-annual variation in local seaice cover. We suggest that, in the Arctic, bivalve growth is governed by food availability. At sites withpronounced sea ice cover, food availability may be linked to sea ice dynamics through the bottom-upregulation exerted by sea ice on phytoplankton production, which renders such areas especially sus-ceptible to future climate change.KEY WORDS: Bivalve · Annual growth · Arctic · Sea ice · Sclerochronology · Marine · Climate
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