Comparative analysis of phytoplankton community structure and stability in the Arabian Sea and Bay of Bengal using eDNA metabarcoding.

Environmental DNA (eDNA) metabarcoding, a non-invasive method for detecting aquatic organisms, has been widely used in phytoplankton diversity assessment. The Arabian Sea (AS) and the Bay of Bengal (BB), the two major ocean basins of the Northern Indian Ocean, exhibit differences in various aspects due to monsoonal influences. However, few eDNA studies have focused on the comparative research on phytoplankton communities in these two regions. To address this gap, in this study, a comparative analysis of phytoplankton community structure and stability was conducted in the AS and BB using eDNA metabarcoding. Clear differences in diversity and composition of phytoplankton communities between the two regions were observed. Higher richness and diversity were found in the BB than in the AS, and the differences in phytoplankton community structure were primarily driven by the nestedness process. Moreover, dinoflagellates were observed as the dominant taxa, and some dinoflagellate taxa showed significant differences between the two regions. Community assembly mechanism analysis revealed that the stochastic processes exhibited a weaker impact in the AS. Stability assessments, which combined co-occurrence network analysis and the metric of average variability degree, revealed higher community stability in the BB. These results not only confirmed the efficacy of eDNA metabarcoding in assessing phytoplankton diversity and stability, but also provided data support for the conservation of aquatic biodiversity and sustainable ecological management in the Northern Indian Ocean.