Influence of ambient geochemical and microbiological variables on the bacterial diversity in a cold seep ecosystem in North Indian Ocean

• Cold seep communities were dominated by Proteobacteria and Firmicutes along the depths. • Down-core variations in bacterial communities showed a rich diversity index in surface sediments. • Role of total organic carbon, labile organic matter, Eh, sulfate, sulfide and methane revealed. Cold seeps are oases for biological communities on the sea floor around hydrocarbon emission pathways. Microbial utilization of methane and other hydrocarbons yield products that fuel rich chemosynthetic communities at these sites. One such site in the cold seep ecosystem of Krishna-Godavari basin (K-G basin) along the east coast of India, discovered in Feb 2018 at a depth of 1800 m was assessed for its bacterial diversity. The seep bacterial communities were dominated by phylum Proteobacteria (57%), Firmicutes (16%) and unclassified species belonging to the family Helicobacteriaceae . The surface sediments of the seep had maximum OTUs (operational taxonomic units) (2.27 × 10 3 ) with a Shannon alpha diversity index of 8.06. In general, environmental parameters like total organic carbon (p < 0.01), sulfate (p < 0.001), sulfide (p < 0.05) and methane (p < 0.01) were responsible for shaping the bacterial community of the cold seep ecosystem in the K-G Basin. Environmental parameters play a significant role in changing the bacterial diversity richness between different cold seep environments in the oceans.