The objective of the study is to explore the microbial diversity at different depths of Arabian Sea Oxygen Minimum Zone (AS-OMZ). Oxygen Minimum Zone (OMZ) is the zone in which oxygen saturation in seawater in the ocean is at its lowest. This zone occurs at depths of about 200 to 1,500 m (660–4,920 ft), depending on local circumstances. Though OMZ constitutes only about 0.1% of the total oceanic volume, about 30–40% of the total oceanic nitrogen loss is estimated to occur within it. The oxygen minimum zone of the Arabian Sea is the thickest of all oceanic OMZs. This study allows us to understand which all organisms contribute maximum to the OMZ and which all organisms can survive in such conditions. Samples were collected from 1000 meter depth station off Kochi.