N2production by denitrification can occur in anoxic water or potentially inside organic particles. Here we compare data from the Black Sea, a permanently anoxic basin, during two organic matter regimes: suspended particulate organic matter concentrations were high in the oxycline after the spring bloom in March 2005 compared to lower organic matter concentrations in June 2005, May and October 2007, July 2008, and May 2001. For all cruises, N2gas had a maximum in the suboxic zone (O2 < 10 μmol/L). During the high organic matter event (March 2005), an additional shallower N2gas and
Genetic markers and geochemical assays of microbial nitrogen cycling processes, including autotrophic and heterotrophic denitrification, anammox, ammonia oxidation, and nitrite oxidation, were examined across the oxycline, suboxic, and anoxic zones of the Cariaco Basin, Venezuela. Ammonia and nitrite oxidation genes were expressed through the entire gradient. Transcripts associated with autotrophic and heterotrophic denitrifiers were mostly confined to the suboxic zone and below but were also present in particles in the oxycline. Anammox genes and transcripts were detected over a narrow depth range near the bottom of the suboxic zone and coincided with secondary NO2−maxima and available NH4+. Dissolved inorganic nitrogen (DIN) amendment incubations and comparisons between our sampling campaigns suggested that denitrifier activity may be closely coupled with NO3−availability. Expression of denitrification genes at depths of high rates of chemoautotrophic carbon fixation and phylogenetic analyses of nitrogen cycling genes and transcripts indicated a diverse array of denitrifiers, including chemoautotrophs capable of using NO3−to oxidize reduced sulfur species. Thus, results suggest that the Cariaco Basin nitrogen cycle is influenced by autotrophic carbon cycling in addition to organic matter oxidation and anammox.
- Publication Date:
- NSF-PAR ID:
- 10367773
- Journal Name:
- Environmental Microbiology
- Volume:
- 23
- Issue:
- 6
- Page Range or eLocation-ID:
- p. 2747-2764
- ISSN:
- 1462-2912
- Publisher:
- Wiley-Blackwell
- Sponsoring Org:
- National Science Foundation
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