Ecological diversity of planktonic protists in spatial regimes of the Arabian Sea revealed through next-generation sequencing

Abstract

Eukaryotic microbes inhabiting diverse ecological niches are capable of mediating biogeochemical shifts. Here, we studied the distribution patterns of protistan community in oxygen-deficient sites in the Arabian Sea and nearby estuarine waters. Protist diversity was quantified through Illumina Miseq sequencing of the V4 region of 18S rRNA gene amplicons. Overall, 12687 OTUs represented the diverse protist communities at various sampling sites such as the open ocean, outer shelf and inner shelf along the oxygen gradient. As per Alpha diversity estimation, estuarine communities were less diverse than the coastal, and open ocean sites. Multivariate analysis was applied to differentiate the community structure in estuarine, coastal and open ocean sites. The results indicated distinct community variation between oxic, hypoxic and suboxic water column at a comparatively deep sea station. However, the influence of dissolved oxygen was statistically insignificant for the protist distribution. The DistLM analysis suggests that the adaptation of protist communities across the spatial habitats could be significantly correlated with temperature, salinity, and nitrate. Moreover, chlorophyll a was the important environmental variable associated with the estuarine complex, whereas salinity, nitrate, and temperature influenced coastal and open ocean stations.