Oxygen minimum zone cryptic sulfur cycling sustained by offshore transport of key sulfur oxidizing bacteria

Abstract

Members of the gammaproteobacterial clade SUP05 couple water column sulfide oxidation to nitrate reduction in sulfidic oxygen minimum zones (OMZs). Their abundance in offshore OMZ waters devoid of detectable sulfide has led to the suggestion that local sulfate reduction fuels SUP05-mediated sulfide oxidation in a so-called “cryptic sulfur cycle”. We examined the distribution and metabolic capacity of SUP05 in Peru Upwelling waters, using a combination of oceanographic, molecular, biogeochemical and single-cell techniques. A single SUP05 species, UThioglobus perditus, was found to be abundant and active in both sulfidic shelf and sulfide-free offshore OMZ waters. Our combined data indicated that mesoscale eddy-driven transport led to the dispersal of UT. perditus and elemental sulfur from the sulfidic shelf waters into the offshore OMZ region. This offshore transport of shelf waters provides an alternative explanation for the abundance and activity of sulfide-oxidizing denitrifying bacteria in sulfide-poor offshore OMZ waters.

Microdiversity and temporal dynamics of marine bacterial dimethylsulfoniopropionate genes

“…B). The SUP05 group is already known to transform inorganic sulfur (Marshall and Morris, ; Shah et al ., ; Callbeck et al ., ) and emerges here as a potential contributor to DMSP cleavage. A second exception is the dddP reads placing to the ‘other Alphaproteobacteria’ cluster containing reference genomes from the Rhizobiales.…”

Facets of diazotrophy in the OMZ off Peru revisited- what we couldn’t see from a single marker gene approach

“…These clades, besides there potential role for N 2 fixation are a first evidence for a euxinic state of the Peruvian OMZ. So far, there were two recent descriptions of this area developing sulfidic anoxia (Callbeck et al 2018;Schunck et al 2013), however, historical reports of Peruvian fishermen on the characteristic smell and black fishing gear , and at least two earlier descriptions of sulfidic anoxia in those waters point towards a re-occurring sulfidic anoxia in this region (Burtt 1852;Dugdale et al 1977). While the presence of indicator species for euxinia is a curious fact, and their presence in the N 2 fixer pool may be important in a future with intensifying, expanding OMZs and more frequent events of sulfidic anoxia as predicted for other waters (Lennartz et al 2014), only the detection of Chlorobium-nif transcripts points towards an involvement in N 2 fixation.…”

“…The oxygen minimum zone (OMZ) off Peru is one of the most prominent examples for expanding and progressing deoxygenation challenging the present ecosystem (Stramma et al 2010). On the Peruvian shelf, anoxic conditions are severe, with locally occurring sulfidic events promoting a microbial community very different from other parts of the OMZ (Callbeck et al 2018;Löscher et al 2015;Schunck et al 2013). Here, the water column is Fe-rich (Löscher et al 2014), and anoxic close to the surface, thus sustaining almost euxinic conditions.…”

A metatranscriptomics‐based assessment of small‐scale mixing of sulfidic and oxic waters on redoxcline prokaryotic communities

“…Vertical and lateral transport processes are believed to be important in shaping the activity and distribution of chemolithoautotrophs in marine oxygen minimum zones. Accordingly, several studies have reported a stimulation of chemolithoautotrophic reactions or transcription of the involved proteins that were induced by such transport processes followed by the mixing of oxygenated and anoxic water bodies (Fuchsman et al ., ; Schmale et al ., ; Callbeck et al ., ; ). On the other hand, the activities of microorganisms unable to utilize and tolerate sulfide may be inhibited after mixing processes in euxinic environments.…”

“…Key players in pelagic redoxclines belong to globally distributed groups in oxygen minimum zones which conduct distinct transformation processes (Wright et al, 2012). For example, representatives of the genus Sulfurimonas within the Campylobacteria and the gammaproteobacterial SUP05 cluster couple sulfur oxidation with autotrophic denitrification and are responsible for the high carbon fixation rates at the oxic-anoxic interface (Walsh et al, 2009;Grote et al, 2012;Glaubitz et al, 2013;Shah et al, 2017;Callbeck et al, 2018). Other key players that were shown to mediate ammonium oxidation in the nitrogenous zone are dominated by Crenarchaeota related to Cand.…”