Biological nitrogen fixation in the oxygen-minimum region of the eastern tropical North Pacific ocean.

Autor: Jayakumar A; Department of Geosciences, Princeton University, Princeton, NJ, USA., Chang BX; Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA, USA.; NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, USA., Widner B; Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA, USA., Bernhardt P; Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA, USA., Mulholland MR; Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA, USA., Ward BB; Department of Geosciences, Princeton University, Princeton, NJ, USA.
Jazyk: angličtina
Zdroj: The ISME journal [ISME J] 2017 Oct; Vol. 11 (10), pp. 2356-2367. Date of Electronic Publication: 2017 Jul 25.
DOI: 10.1038/ismej.2017.97
Abstrakt: Biological nitrogen fixation (BNF) was investigated above and within the oxygen-depleted waters of the oxygen-minimum zone of the Eastern Tropical North Pacific Ocean. BNF rates were estimated using an isotope tracer method that overcame the uncertainty of the conventional bubble method by directly measuring the tracer enrichment during the incubations. Highest rates of BNF (~4 nM day -1 ) occurred in coastal surface waters and lowest detectable rates (~0.2 nM day -1 ) were found in the anoxic region of offshore stations. BNF was not detectable in most samples from oxygen-depleted waters. The composition of the N 2 -fixing assemblage was investigated by sequencing of nifH genes. The diazotrophic assemblage in surface waters contained mainly Proteobacterial sequences (Cluster I nifH), while both Proteobacterial sequences and sequences with high identities to those of anaerobic microbes characterized as Clusters III and IV type nifH sequences were found in the anoxic waters. Our results indicate modest input of N through BNF in oxygen-depleted zones mainly due to the activity of proteobacterial diazotrophs.
Databáze: MEDLINE
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