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

摘要: Abstract. The potential coupling of nitrogen (N2) fixation and sulfate reduction (SR) was explored in sediments the Peruvian oxygen minimum zone (OMZ). Sediment samples were retrieved by a multiple corer at six stations along depth transect (70–1025 m water depth) 12° S, covering anoxic hypoxic bottom conditions. Benthic N2 fixation, determined acetylene assay, detected all sites, with highest rates between 70 253 m lower greater depth. SR decreased increasing overlapped sediments, suggesting both processes. However, weak positive correlation their activity distribution principle component analysis. A link sulfate-reducing bacteria indicated molecular analysis nifH genes. Detected sequences clustered Desulfonema limicola station. other uncultured organisms, Gammaproteobacteria, Firmicutes (Clostridia) rather than known reducers. revealed that benthic OMZ is controlled organic matter (positive) free sulfide (negative). No found ammonium concentrations (even levels > 2022 µM). same range as those measured organic-rich sediments.