MEPS 389:149-158 (2009)  -  DOI: https://doi.org/10.3354/meps08200

ABSTRACT: Sea ice exerts a strong influence on Arctic marine primary production, thereby influencing food availability for secondary producers. Food availability is recognized as one of the primary constraints on macrobenthic growth and production. Thus, it may be expected that spatial and temporal variability in Arctic sea ice cover influencing primary productivity could translate to the next trophic level: the benthic secondary producers. To test whether sea ice cover is coupled to the annual production 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 from sub-Arctic to high-Arctic Greenland, and (2) produce time series of inter-annual variation in bivalve growth at sites with different sea ice conditions. A significant difference between average individual growth rates between the different sites was found. This geographic variation in growth performance was correlated to the average productive open-water (ice-free) period estimated from sea ice data obtained 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 ice cover, bivalve growth was reduced to 35 to 45% of the maximum growth rates. At these 2 sites the year-to-year variation in bivalve growth correlated negatively with inter-annual variation in local sea ice cover. We suggest that, in the Arctic, bivalve growth is governed by food availability. At sites with pronounced sea ice cover, food availability may be linked to sea ice dynamics through the bottom-up regulation exerted by sea ice on phytoplankton production, which renders such areas especially susceptible to future climate change.

KEY WORDS: Bivalve · Annual growth · Arctic · Sea ice · Sclerochronology · Marine · Climate