Metagenomic insights into bacterial dynamics and niche partitioning in response to varying oxygen gradients in the Arabian Sea oxygen minimum zone (OMZ)

Abstract

This study investigates the impact of oxygen gradients on bacterial diversity and community composition within the Arabian Sea oxygen minimum zone (OMZ), providing insight into their ecology in this unique environment. Vertical profiling of physicochemical parameters and bacterial community composition was conducted at two stations within the OMZ using Illumina sequencing of the V3-V4 regions of the 16S rRNA gene. The oxygen levels in the water column of the study locations varied from oxic to hypoxic and Station-I exhibited intense anoxic conditions. Bacterial diversity analyses revealed a rich assemblage of 24 bacterial phyla dominated by Proteobacteria, with significant presence of Actinobacteria and Planctomycetes. SIMPER (Similarity percentage) analysis highlights taxa such as Synechococcophycideae, Flavobacteriia in oxic water and Phycisphaerae as significant contributors to community dissimilarity in oxygen-deficient water, emphasizing their ecological roles in nutrient cycling and the impact of oxygen availability on marine biodiversity. Canonical Correspondence Analysis (CCA) further elucidates the relationships between bacterial communities and environmental variables, with oxygen, temperature, and nutrient concentrations playing crucial roles in shaping bacterial community distributions. This research enhances our understanding of microbial ecology in the Arabian Sea OMZ by revealing how microbial communities respond to changing oxygen conditions, providing insights into the ecological dynamics of the region. Furthermore, these findings underscore the need for continued research to predict and mitigate the effects of environmental changes on marine ecosystems, particularly in the context of expanding OMZs and global biogeochemical cycles.