title: Giant hydrogen sulfide plume in the oxygen minimum zone off Peru supports chemolithoautotrophy.
abstract: In Eastern Boundary Upwelling Systems nutrient-rich waters are transported to the ocean surface, fuelling high photoautotrophic primary production. Subsequent heterotrophic decomposition of the produced biomass increases the oxygen-depletion at intermediate water depths, which can result in the formation of oxygen minimum zones (OMZ). OMZs can sporadically accumulate hydrogen sulfide (H2S), which is toxic to most multicellular organisms and has been implicated in massive fish kills. During a cruise to the OMZ off Peru in January 2009 we found a sulfidic plume in continental shelf waters, covering an area >5500 km(2), which contained ∼2.2×10(4) tons of H2S. This was the first time that H2S was measured in the Peruvian OMZ and with ∼440 km(3) the largest plume ever reported for oceanic waters. We assessed the phylogenetic and functional diversity of the inhabiting microbial community by high-throughput sequencing of DNA and RNA, while its metabolic activity was determined with rate measurements of carbon fixation and nitrogen transformation processes. The waters were dominated by several distinct γ-, δ- and ε-proteobacterial taxa associated with either sulfur oxidation or sulfate reduction. Our results suggest that these chemolithoautotrophic bacteria utilized several oxidants (oxygen, nitrate, nitrite, nitric oxide and nitrous oxide) to detoxify the sulfidic waters well below the oxic surface. The chemolithoautotrophic activity at our sampling site led to high rates of dark carbon fixation. Assuming that these chemolithoautotrophic rates were maintained throughout the sulfidic waters, they could be representing as much as ∼30% of the photoautotrophic carbon fixation. Postulated changes such as eutrophication and global warming, which lead to an expansion and intensification of OMZs, might also increase the frequency of sulfidic waters. We suggest that the chemolithoautotrophically fixed carbon may be involved in a negative feedback loop that could fuel further sulfate reduction and potentially stabilize the sulfidic OMZ waters.
authors.affiliation: Research Division Marine Biogeochemistry, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany ; Institute for General Microbiology, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Schunck
authors.forename: Gaute
authors.initials: G
authors.lastname: Lavik
authors.forename: Dhwani K
authors.initials: DK
authors.lastname: Desai
authors.forename: Tobias
authors.initials: T
authors.lastname: Großkopf
authors.forename: Tim
authors.initials: T
authors.lastname: Kalvelage
authors.forename: Carolin R
authors.initials: CR
authors.lastname: Löscher
authors.forename: Aurélien
authors.initials: A
authors.lastname: Paulmier
authors.forename: Sergio
authors.initials: S
authors.lastname: Contreras
authors.forename: Herbert
authors.initials: H
authors.lastname: Siegel
authors.forename: Moritz
authors.initials: M
authors.lastname: Holtappels
authors.forename: Philip
authors.initials: P
authors.lastname: Rosenstiel
authors.forename: Markus B
authors.initials: MB
authors.lastname: Schilhabel
authors.forename: Michelle
authors.initials: M
authors.lastname: Graco
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Schmitz
authors.forename: Marcel M M
authors.initials: MM
authors.lastname: Kuypers
authors.forename: Julie
authors.initials: J
authors.lastname: Laroche
mesh_terms: D001419:Bacteria / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D018533:Biomass; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000737:chemistry; D052837:Chemoautotrophic Growth / Q000502:physiology*; D016000:Cluster Analysis; D003102:Colloids / Q000737:chemistry; D017753:Ecosystem; D005434:Flow Cytometry / Q000379:methods; D016680:Genome, Bacterial; D006862:Hydrogen Sulfide / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D010140:Pacific Ocean; D010568:Peru; D010802:Phylogeny; D012623:Seawater / Q000737:chemistry*; D017422:Sequence Analysis, DNA; D017423:Sequence Analysis, RNA; D013440:Sulfides / Q000737:chemistry; D014871:Water Microbiology
chemical_list: D003102:Colloids; D013440:Sulfides; D002245:Carbon Dioxide; D009584:Nitrogen; D010100:Oxygen; D006862:Hydrogen Sulfide