Benthic infauna of the seasonally ice-covered western Barents Sea: Patterns and relationships to environmental forcing

The northwestern Barents Sea and Svalbard archipelago are influenced by both warm Atlantic and cold Arctic water masses. We investigated infaunal benthic community structure in Atlantic- and Arctic-dominated areas, and at the Barents Sea Polar Front in order to assess the patterns of variability and to examine the influence of environmental variables on benthic fauna in this region. As part of the CABANERA program, we sampled 14 stations between 2003 and 2005 for benthic infaunal community composition, density, and biomass. Stations were in offshore shelf locations with soft sediments ranging in depth from 200 to 500 m, and encompassed different water mass characteristics and a wide range of other environmental conditions. Benthic biomass averaged 66 g WW m−2 (range 10–152 g WW m−2), mean density was 4340 ind. m−2 (1970–7896 ind. m−2), and species richness varied from 71–192 taxa stn.−1. Community structure was reflective of large-scale oceanography, as stations clustered in groups related to predominant water masses. Patterns in faunal density and biomass were largely determined by sedimentary characteristics, with water temperature, depth, and annual primary production also influencing some community parameters. Organism density and species richness were 86% and 44% greater at stations located near the Polar Front, compared to stations located in either Atlantic- or Arctic-dominated water masses. This pattern is coincident with elevated primary production at the Polar Front (48% compared to Atlantic- or Arctic-dominated water), suggesting a direct link between food availability in the Barents Sea and the benthic community structure. This leads to the conclusion that benthic communities in northwestern Barents Sea region are food-limited, and strongly dependent on predictable, albeit episodic, delivery of organic matter from the water column. Climatic processes leading to long-term changes in the location of the Polar Front will therefore have impacts on community structure and function on the sea floor.