Program and Agenda

Abstract

MICROBIAL BENTHIC NITROGEN FIXATION INSIDE AND BELOW THE PERUVIAN OXYGEN MINIMUM ZONE

Despite its potential to provide bioavailable nitrogen (N) to the benthos, occurrence and drivers of N-fixation in marine sediments are still poorly understood. We investigated benthic N-fixation in the Peruvian oxygen minimum zone (OMZ), along a latitudinal depth transect (70–1025 m water depth), covering anoxic and hypoxic bottom water conditions in sediments retrieved by a multicorer and benthic lander. N-fixation was detected at all sites. Highest N-fixation rates were measured in sediments, covered with microbial mats formed by sulfur bacteria, in water depth from 70 to 244 m. The highest integrated N-fixation rate of 0.23 mmol N/m2/d (0-20 cm sediment depth) was measured inside the core of the OMZ at 244 m water depth, coinciding with a maximum of N release and low ammonium release that was determined in benthic chambers. Lowest N-fixation rates were determined below 244 m down to 1025 m water depth. Sequencing data revealed the occurrence of the functional gene for N-fixation, belonging to new clusters of diazotrophs. The coupling between N-fixation and sulfate reduction and incorporation of 15N into microbial biomass will be discussed.

Authors

Gier, J., GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, jgier@geomar.de

Sommer, S., GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, ssommer@geomar.de

Loescher, C., Institut für Allgemeine Mikrobiologie/Christian-Albrechts-Universität Kiel, Germany, cloescher@geomar.de

Schmitz-Streit, R., Institut für Allgemeine Mikrobiologie/Christian-Albrechts-Universität Kiel, Germany, rschmitz@ifam.uni-kiel.de

Treude, T., GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, ttreude@geomar.de

Details

Oral presentation

Session #:125
Date: 2/24/2014
Time: 09:30
Location: 301 AB

Presentation is given by student: Yes