Different temperature adaptation in Arctic and Atlantic heterotrophic bacteria in the Barents Sea Polar Front region

Abstract

In the northern Barents Sea, at and around the Polar Front, carbon cycle variables were investigated during 2weeks in late summer of 2007. Arctic Water primary production in the experimental period averaged 50mmol C m−2day−1, as estimated from satellite sensed chlorophyll. In Atlantic waters, which appeared to just have passed the culmination of a late summer bloom, primary production was 125mmol C m−2day−1. Total organic carbon (TOC) averaged 82.4μM C in the mixed layer, and the values showed a gradient with highest values to the southeast and lowest to the northwest. The distribution of TOC was not related to the distribution of Atlantic and Arctic waters, although the highest values were found in Atlantic Water. Integrated bacterial production in the mixed layer, as estimated from thymidine incorporation rates, averaged 6.3% of primary production. In Atlantic Water, over the depth of the mixed layer, bacterial production rate averaged 0.40mmol C m−3day−1, which was 6.6 times the average in Arctic Water and 2.3 times the average in the front regions. Below 30m depth, bacterial production rates were generally higher in the Arctic Water than in the Atlantic Water. Moreover, when production rates of bacteria were compared according to temperature, the rates in Arctic Water were systematically higher than the rates in Atlantic Water. This difference implies that the heterotrophic bacteria from the Arctic have adapted towards higher growth efficiency than the bacteria in Atlantic Water.