Unveiling the faunal diversity in the water column adjacent to two seamounts in the deep Arabian Sea using environmental DNA metabarcoding

Abstract

The diversity of organisms inhabiting deep-sea ecosystems, such as seamounts, has hitherto remained under-studied. In this study, we report on the faunal diversity in the water column adjacent to the summit and periphery of two seamounts (SMS2 and SMS3) and an oxygen minimum zone site located away from the seamounts in the southeast Arabian Sea. Environmental DNA (eDNA) in the water column was metabarcoded using the Cytochrome Oxidase C subunit I (COI) gene marker and Oxford Nanopore sequencing technology. Hydrographic conditions revealed that the summits of the seamounts intersect with the core oxygen minimum zone between depths of 300 and 600 m. Comparisons of COI gene sequences with those in available databases, MIDORI and BOLD, indicated the existence of a diverse group of novel organisms in the study area. Crustaceans dominated (75-95%) in the summit and periphery of the SMS2 and the OMZ site, while Cnidaria (56-63%) and Chordata (55%), respectively, dominated the summit and periphery of SMS3. Overall, the current study highlights the broad diversity of organisms living in the water column around the seamounts and underscores the potential of eDNA for exploring them.