Nitrogen fixation in sediments along a depth transect through the Peruvian oxygen minimum zone.

Gier, Jessica, Sommer, Stefan, Löscher, Carolin R., Dale, Andrew W. , Schmitz-Streit, Ruth and Treude, Tina (2016) Nitrogen fixation in sediments along a depth transect through the Peruvian oxygen minimum zone. Open Access Biogeosciences (BG), 13 . pp. 4065-4080. DOI 10.5194/bg-13-4065-2016.

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Benthic nitrogen (N2) fixation and sulfate reduction (SR) were investigated in the Peruvian oxygen minimum zone (OMZ). Sediment samples, retrieved by a multiple corer were taken at six stations (70–1025 m) along a depth transect at 12° S, covering anoxic and hypoxic bottom water conditions. Benthic N2 fixation was detected at all sites, with high rates measured in OMZ mid-waters between the 70 and 253 m and lowest N2 fixation rates below 253 m down to 1025 m water depth. SR rates were decreasing with increasing water depth, with highest rates at the shallow site. Benthic N2 fixation depth profiles largely overlapped with SR depth profiles, suggesting that both processes are coupled. The potential of N2 fixation by SR bacteria was verified by the molecular analysis of nifH genes. Detected nifH sequences clustered with SR bacteria that have been demonstrated to fix N2 in other benthic environments. Depth-integrated rates of N2 fixation and SR showed no direct correlation along the 12° S transect, suggesting that the benthic diazotrophs in the Peruvian OMZ are being controlled by additional various environmental factors. The organic matter availability and the presence of sulfide appear to be major drivers for benthic diazotrophy. It was further found that N2 fixation was not inhibited by high ammonium concentrations. N2 fixation rates in OMZ sediments were similar to rates measured in other organic-rich sediments. Overall, this work improves our knowledge on N sources in marine sediments and contributes to a better understanding of N cycling in OMZ sediments.

Document Type: Article
Keywords: Nitrogen, Peruvian oxygene minimum zone, RV Meteor, M92
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Kiel University > Kiel Marine Science
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 754
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Kiel University
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-13-4065-2016
ISSN: 1726-4189
Projects: SFB754, Future Ocean
Date Deposited: 03 Sep 2015 10:12
Last Modified: 01 Feb 2019 15:06

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