Metagenomic derived insights of microbial communities in the Southern Indian Ocean

Abstract

To understand the oceanographic features, how they shape marine microbial ecosystems and their implications on biogeochemical cycling remains a major ecological endeavor. Recently, several studies have assessed the contribution of photoautotrophs in surface waters and related factors which shape them. However, in contrast very little is known regarding chemolithoautotrophs in the marine ecosystems generally and waters south of 40 degrees. Here, we assess microbial diversity, and functional capacity along the Agulhas current system and the Subtropical convergence in the South Indian Ocean. Samples collected from three water columns, epipelagic zone, oxygen minimum zone (OMZ. and bathypelagic zone, were analysed using shotgun metagenomics. We found high taxonomic richness in surface and deep water sample, with generally low numbers for middle samples, corresponding to the oxygen minimum zones, in contrast to other marine environments. Community analysis revealed significant dissimilarity between the three water depths; dominated by marine Proteobacteria, followed by Bacteroidetes, Actinobacteria, and Firmicutes with strikingly low relative abundance of Cyanobacteria. Our data showed evidence of extensive carbon, nitrogen and sulfur biogeochemical cycling genetic capacity with a large proportion of functional genes belonging to Alphaproteobacteria (Rhizobiales., Gammaproteobacteria (genus Pseudoalteromonas. and Cyanobacteria (genus Synechococcus.. We have reconstructed the bacterial genome bins using bioinformatics tools. The most completed genome bin shows highest similarity to the genusPsychrobacter, having genes for the sulfur and iron metabolism, suitable for the South Indian Ocean marine environment. Taken together, our results suggest differential microbial community structure along with the water columns. Functional analysis revealed a variety of traits driven by these taxa together with Proteobacteria, suggesting high functional redundancy. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.