Preprints
https://doi.org/10.5194/bg-2021-25
https://doi.org/10.5194/bg-2021-25

  12 Feb 2021

12 Feb 2021

Review status: this preprint is currently under review for the journal BG.

Sedimentation rate and organic matter dynamics shape microbiomes across a continental margin

Sabyasachi Bhattacharya1, Tarunendu Mapder2,a,, Svetlana Fernandes3,, Chayan Roy1,, Jagannath Sarkar1,, Moidu Jameela Rameez1, Subhrangshu Mandal1, Abhijit Sar4, Amit Kumar Chakraborty5, Nibendu Mondal1, Sumit Chatterjee1, Bomba Dam4, Aditya Peketi3, Ranadhir Chakraborty6, Aninda Mazumdar3, and Wriddhiman Ghosh1 Sabyasachi Bhattacharya et al.
  • 1Department of Microbiology, Bose Institute, P-1/12 CIT Scheme VIIM, Kolkata - 700054, West Bengal, India
  • 2Department of Chemistry, Bose Institute, 93/1 APC Road, Kolkata - 700009, India
  • 3Gas Hydrate Research Group, Geological Oceanography, CSIR National Institute of Oceanography, Dona Paula, Goa - 403004, India
  • 4Department of Botany, Institute of Science, Visva-Bharati, Santiniketan, West Bengal - 731235, India
  • 5Department of Environmental studies, Institute of Science, Visva-Bharati, Santiniketan, West Bengal - 731235, India
  • 6Department of Biotechnology, University of North Bengal, Siliguri, West Bengal 734013, India
  • apresent address: Division of Clinical Pharmacology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
  • Equal contributions

Abstract. Marine sedimentation rate and bottom-water O2 concentration control the remineralization/sequestration of organic carbon across continental margins; but whether/how they shape microbiome architecture (the ultimate effector of all biogeochemical phenomena), across shelf/slope sediments, is unknown. Here we reveal distinct microbiome structures and functions, amidst comparable pore fluid chemistries, along 300 cm sediment horizons underlying the seasonal (shallow coastal) and perennial (deep sea) oxygen minimum zones (OMZs) of the Arabian Sea, situated across the western-Indian margin (water-depths: 31 m and, 530 and 580 m, respectively). The sedimentary geomicrobiology was elucidated by analyzing metagenomes, metatranscriptomes, and enrichment cultures, and also sedimentation rates measured by radiocarbon and lead excess (210Pbxs); the findings were then evaluated in the light of the other geochemical data available for the cores investigated. Along the perennial- and seasonal-OMZ sediment cores, microbial communities were dominated by Gammaproteobacteria and Alphaproteobacteria, and Euryarchaeota and Firmicutes, respectively. As a perennial-OMZ signature, a cryptic methane production-consumption cycle was found to operate near the sediment-surface (within the sulfate reduction zone); overall diversity, as well as the relative abundances of simple-fatty-acids-requiring anaerobes (methanogens, anaerobic methane-oxidizers, sulfate-reducers and acetogens), peaked in the topmost sediment-layer and then declined via synchronized fluctuations until the sulfate-methane transition zone was reached. The entire microbiome profile was reverse in the seasonal-OMZ sediment horizon. In the perennial-OMZ sediments organic carbon deposited was higher in concentration and marine components-rich, so it potentially degraded readily to simple fatty acids; lower sedimentation rate afforded higher O2 exposure time for organic matter degradation despite perennial hypoxia in the bottom-water; thus, the resultant abundance of reduced carbon substrates sustained multiple inter-competing microbial processes in the upper sediment-layers. Remarkably, the whole geomicrobial scenario was opposite in the sediments of the seasonal/shallow-water OMZ. Our findings create a microbiological baseline for understanding carbon-sulfur cycling across distinct marine depositional settings and water-column oxygenation regimes.

Sabyasachi Bhattacharya et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-25', Anonymous Referee #1, 14 Mar 2021
  • RC2: 'Comment on bg-2021-25', Anonymous Referee #2, 15 Mar 2021

Sabyasachi Bhattacharya et al.

Sabyasachi Bhattacharya et al.

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Short summary
Physicochemical determinants of microbiome architecture across continental shelves/slopes are unknown, so we explored the geomicrobiology along 3 m sediment horizons of the seasonal (shallow coastal) & perennial (deep sea) hypoxic zones of the eastern Arabian Sea. Nature, concentration & fate of the organic matter delivered to the seafloor were found to shape the microbiome across the western Indian margin, under direct/indirect influence of sedimentation-rate/water-column-O2-level respectively.
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