Pathways of carbon oxidation in an Arctic fjord sediment (Svalbard) and isolation of psychrophilic and psychrotolerant Fe(III)-reducing bacteria

• Main Authors: Vandieken, V., Finke, N., Jørgensen, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2006
• Subjects: Svalbard
• Online Access: http://hdl.handle.net/21.11116/0000-0001-CFB3-C; http://hdl.handle.net/21.11116/0000-0007-8B5C-6

The main mineralization pathways were determined in permanently cold fjord sediment on the west coast of Svalbard. In whole core incubations, the total oxygen uptake rate was 4.2 ± 0.4 mmol m–2 d–1 and the sulfate reduction rate 2.6 ± 0.6 mmol m–2 d–1 at 0 to 20 cm depth. Sulfate reduction was the most important anaerobic mineralization process, accounting for 57% of anaerobic organic carbon oxidation in anoxic bag incubations of the top 5 cm of the sediment. The remaining 43% oxidation was attributed to microbial Fe(III) reduction. Both processes occurred concurrently in the uppermost 2 cm, and the Fe-reducing community appeared to be limited mainly by the availability of Fe(III). Below 2 cm, sulfate reduction was the dominant electron-accepting process. Calculations for the uppermost 10 cm of the sediment yielded the following contribution of the different respiratory pathways to total carbon oxidation: aerobic respiration 53%, sulfate reduction 34%, Fe(III) reduction 13%. In situ, the importance of Fe(III) reduction may vary through competition for substrate with oxygen- and nitrate-reducing bacteria in the surface sediment. Fe(III)-reducing bacteria belonging to the genera Desulfuromonas, Desulfuromusa, Shewanella and Desulfovibrio were isolated from enrichment cultures of 2 fjord sediments from Svalbard. Strains related to Desulfovibrio reduced Fe(III) without energy generation for growth. All isolates were psychrophilic or psychrotolerant and grew at –2°C, the freezing point of sea water, indicating adaptation to permanently cold temperatures. Besides Fe(III), the strains reduced other electron acceptors such as oxygen, manganese, elemental sulfur and sulfate.