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

ABSTRACT

The Northern Indian Ocean hosts two Oxygen Minimum Zones (OMZ), one in the Arabian Sea and the other in the Bay of Bengal. 16S rRNA gene amplicon sequencing was used to understand the total bacterial diversity in, the surface sediment off Goa within the OMZ of the Arabian Sea, and off Paradeep within the OMZ of the Bay of Bengal. Functional profiling was carried out to pinpoint the occurrence of specific bacterial operational taxonomic units (OTUs) which have been previously described to harbour certain genes/enzymes relevant to biogeochemical cycling of carbon, nitrogen, and sulfur compounds. 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 revealed some major differences regarding sediment nitrogen fixation and carbon recycling, and identified a distinct bacterial community structure within the two shallow OMZ sites lying in the east coast and west coast of the peninsular India.

KEYWORDS:

• OMZ
• sediment bacteria
• 454 pyrosequencing
• Arabian Sea
• Bay of Bengal
• functional ecology

Acknowledgments

We thank the Director of CSIR-NIO for providing the facilities. We acknowledge Chun Lab, Seoul, South Korea, for carrying out pyrosequencing. Special thanks to Dr Carolin Löscher for the critical comments and valuable suggestions which have significantly helped in improvising the content. We express our gratitude to Dr Amal Jayakumar, Dr N. Ramaiah and Dr Peter Burkill for guidance in manuscript preparation. We acknowledge the contributions of anonymous reviewers of this journal. We also thank crew members of SSK-046 and SSD-002, especially Ms Larissa Menezes, for GS1A sample collection. JL prepared the manuscript and performed the experiments and bioinformatics analysis. CSM supervised the research.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All pyrosequencing reads were submitted to the NCBI GenBank database under accession number KU821783 – KU831324 and MG860544 – MG860851.

Additional information

Funding

The first author is grateful to the Council of Scientific and Industrial Research (CSIR), India, for fellowship grant 31/026(0245)/2012-EMR-I for doing a PhD. This work is supported by CSIR grant: PSC0108. NIO's contribution no: 6614.