AME 21:115-123 (2000)  -  doi:10.3354/ame021115

Bacterial production rates and concentrations of organic carbon at the end of the growing season in the Greenland Sea

Knut Yngve Børsheim*

Department of Biotechnology, The Norwegian University of Science and Technology, 7491 Trondheim, Norway

ABSTRACT: Profiles from the euphotic zone at the end of July in the Greenland Sea showed that bacterial production rates were highest in surface Arctic domain water, and generally lower in locations from the warmer North Atlantic domain. Bacterial production from all locations investigated averaged 0.26 μM C d-1 in the upper 50 m water column, and the 0 to 50 m integrated bacterial production averaged 67% of the 0 to 500 m integrated production. Both bacterial total counts and growth rates were high compared to other oligotrophic open ocean areas. In the upper 50 m water column, bacterial total counts averaged 1.1 ×106 cells ml-1, and bacterial growth rate averaged 0.68 d-1. The high bacterial growth rate and production rate may be related to the fact that at the end of the productive season considerable amounts of annually produced transient organic material were present. The amount of organic material that had accumulated through the productive season was estimated by comparing profiles of TOC measured at the end of July with winter values, and with values of TOC from 1000 m depth and below. The amount of transient TOC in the upper 50 m averaged 1.15 mol C m-2, and ranged from 0.68 to 1.5 mol C m-2. Based on an assumed bacterial growth yield of 30%, the measured bacterial production rates in the upper 50 m inferred a turnover of the transient TOC in the range of 8 to 91 d.

KEY WORDS: Bacterial production · TOC · DOC · Greenland Sea · Carbon cycle

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