Biogeochemistry of the Black Sea Anoxic Zone With a Reference to Sulphur Cycle

Neretin, Lev N.; Volkov, I. I.; Rozanov, A. G.; Demidova, T. A.; Falina, Anastasiya S.

doi:10.1007/1-4020-4297-3_04

Cited by 8 publications

(4 citation statements)

References 52 publications

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“…In the current Black Sea, microbial cycling of sulfur takes place at depths at and below the sulfidic chemocline (~100 m) (Neretin, Volkov, Rozanov, Demidova, & Falina, ) (Pimenov & Neretin, ). In our core, we found ORFs of both aerobic and anaerobic bacteria involved in sulfur cycling (Figures and ).…”

Section: Discussionmentioning

confidence: 99%

Holocene paleodepositional changes reflected in the sedimentary microbiome of the Black Sea

Giosan

Grice

et al. 2019

Geobiology

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Subsurface microbial communities are generally thought to be structured through in situ environmental conditions such as the availability of electron acceptors and donors and porosity, but recent studies suggest that the vertical distribution of a subset of subseafloor microbial taxa, which were present at the time of deposition, were selected by the paleodepositional environment. However, additional highly resolved temporal records of subsurface microbiomes and paired paleoenvironmental reconstructions are needed to justify this claim. Here, we performed a highly resolved shotgun metagenomics survey to study the taxonomic and functional diversity of the subsurface microbiome in Holocene sediments underlying the permanently stratified and anoxic Black Sea. Obligate aerobic bacteria made the largest contribution to the observed shifts in microbial communities associated with known Holocene climate stages and transitions. This suggests that the aerobic fraction of the subseafloor microbiome was seeded from the water column and did not undergo post‐depositional selection. In contrast, obligate and facultative anaerobic bacteria showed the most significant response to the establishment of modern‐day environmental conditions 5.2 ka ago that led to a major shift in planktonic communities and in the type of sequestered organic matter available for microbial degradation. No significant shift in the subseafloor microbiome was observed as a result of environmental changes that occurred shortly after the marine reconnection, 9 ka ago. This supports the general view that the marine reconnection was a gradual process. We conclude that a high‐resolution analysis of downcore changes in the subseafloor microbiome can provide detailed insights into paleoenvironmental conditions and biogeochemical processes that occurred at the time of deposition.

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Section: Discussionmentioning

confidence: 99%

Holocene paleodepositional changes reflected in the sedimentary microbiome of the Black Sea

Giosan

Grice

et al. 2019

Geobiology

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“…The Black Sea is one of the most isolated seas from the ocean. The near‐isolation, along with a strong vertical stratification, has led to formation of a thick column of vertically stagnant anoxic water in the Black Sea from about 150 m depth to the bottom [ Neretin et al ., ]. Hydrographic properties of this water column are stable on seasonal to interdecadal timescales and almost uniform laterally along isopycnal surfaces [ Mamaev et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Observed basin‐wide propagation of Mediterranean water in the Black Sea

et al. 2017

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Mediterranean water entering the Black Sea through the Bosphorus Strait forms middepth intrusions that contribute to the salt, heat, and volume balances of the sea, ventilate its water column at intermediate depths and restrain the upward flux of hydrogen sulfide from deeper layers. Despite the importance for the Black Sea environment, the circulation of Mediterranean‐origin water in the basin is fundamentally underexplored. Here we use hydrographic data collected from ships and Argo profiling floats to identify pathways of the Mediterranean intrusions in the general circulation system of the sea. While earlier the intrusions were observed primarily near the Bosphorus Strait, we present an evidence for their intermittent extensive propagation throughout the basin. We find that the main conduit for the intrusions is the southern limb of the Rim Current that carries the intruded water from the Bosphorus Strait eastward. A part of this eastward flow recirculates cyclonically into the interior of the sea, where traces of the intrusions gradually disappear because of mixing. We put forward the hypothesis that the formation of the most prominent intrusions is associated with strong cyclonic storms over the Bosphorus Strait, which lead to abnormally large influx of Mediterranean water.

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“…One interesting site for such studies is the Black Sea, the largest anoxic basin in the world. A major characteristic of this environment is the presence of a stable halocline that separates the brackish and oxic surface layer from a more saline, 2000 m deep anoxic water column, in which the H 2 S concentration could reach 375 μM (Neretin et al ., 2006). As the lower part of the water column is anoxic and highly sulfidic, the zonation of redox processes in the Black Sea sediment is not as diverse as normally observed in marine sediments.…”

Section: Introductionmentioning

confidence: 99%

Diversity and abundance of sulfate‐reducing microorganisms in the sulfate and methane zones of a marine sediment, Black Sea

Leloup

Loy

Knab

et al. 2006

Environmental Microbiology

239

221

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The Black Sea, with its highly sulfidic water column, is the largest anoxic basin in the world. Within its sediments, the mineralization of organic matter occurs essentially through sulfate reduction and methanogenesis. In this study, the sulfate-reducing community was investigated in order to understand how these microorganisms are distributed relative to the chemical zonation: in the upper sulfate zone, at the sulfate-methane transition zone, and deeply within the methane zone. Total bacteria were quantified by real-time PCR of 16S rRNA genes whereas sulfate-reducing microorganisms (SRM) were quantified by targeting their metabolic key gene, the dissimilatory (bi)sulfite reductase (dsrA). Sulfate-reducing microorganisms were predominant in the sulfate zone but occurred also in the methane zone, relative proportion was maximal around the sulfate-methane transition, c. 30%, and equally high in the sulfate and methane zones, 5-10%. The dsrAB clone library from the sulfate-methane transition zone, showed mostly sequences affiliated with the Desulfobacteraceae. While, the dsrAB clone libraries from the upper, sulfate-rich zone and the deep, sulfate-poor zone were dominated by similar, novel deeply branching sequences which might represent Gram-positive spore-forming sulfate- and/or sulfite-reducing microorganisms. We thus hypothesize that terminal carbon mineralization in surface sediments of the Black Sea is largely due to the sulfate reduction activity of previously hidden SRM. Although these novel SRM were also abundant in sulfate-poor, methanogenic areas of the Black Sea sediment, their activities and possibly very versatile metabolic capabilities remain subject of further study.

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Biogeochemistry of the Black Sea Anoxic Zone With a Reference to Sulphur Cycle

Cited by 8 publications

References 52 publications

Holocene paleodepositional changes reflected in the sedimentary microbiome of the Black Sea

Holocene paleodepositional changes reflected in the sedimentary microbiome of the Black Sea

Observed basin‐wide propagation of Mediterranean water in the Black Sea

Diversity and abundance of sulfate‐reducing microorganisms in the sulfate and methane zones of a marine sediment, Black Sea

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