14 May 2020
 | 14 May 2020
Status: this discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

A comparison of bacterial communities from OMZ sediments in the Arabian Sea and the Bay of Bengal reveals major differences in nitrogen turnover and carbon recycling potential

Jovitha Lincy and Cathrine Sumathi Manohar

Abstract. The Northern Indian Ocean hosts two Oxygen Minimum Zones (OMZ), one in the Arabian Sea and the other in the Bay of Bengal. High-throughput sequencing was used to understand the total bacterial diversity in, the surface sediment off Goa within the OMZ of the Arabian Sea, and from off Paradip within the OMZ of the Bay of Bengal. The dominant phyla identified included Firmicutes (33.08 %) and Proteobacteria (32.59 %) from the Arabian Sea, and Proteobacteria (52.65 %) and Planctomycetes (9.36 %) from the Bay of Bengal. Only 30 % of OTUs were shared between the sites which make up three-fourth of the Bay of Bengal OMZ bacterial community, but only one-fourth of the Arabian Sea OMZ sediment bacterial community. Statistical analysis indicated the bacterial diversity from sediments of the Bay of Bengal OMZ is ~ 48 % higher than the Arabian Sea OMZ. The community analysis combined with a predictive functional profiling of 16S rRNA amplicons pinpointed the occurrence of specific enzymes that are crucial in the cycling of nitrogen and sulfur compounds, with major differences regarding nitrogen fixation and carbon recycling.

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Jovitha Lincy and Cathrine Sumathi Manohar
Jovitha Lincy and Cathrine Sumathi Manohar
Jovitha Lincy and Cathrine Sumathi Manohar


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Short summary
We report on sediment microbial communities from the two basins of the northern Indian Ocean, namely the Arabian Sea and the Bay of Bengal. We used a comparative amplicon sequencing, biogeochemical analysis and metagenomic modeling to explore the microbial communities and predict their metabolic potential. This revealed the potential for different pathways of respiration and organic matter turnover, which may add to understanding why the two basins are different in their oxygen concentrations.