Diversity of picoeukaryotes in the eastern equatorial Indian Ocean revealed by metabarcoding

Abstract

We used 18S rRNA gene metabarcoding to investigate picoeukaryotic diversity and distribution at the surface and deep chlorophyll maximum (DCM) of 4 stations in the eastern equatorial Indian Ocean (EEIO). The results showed that picoeukaryotic communities were dominated by 5 phyla: Dinoflagellata, Radiolaria, Chlorophyta, Ochrophyta and Ciliophora. The picoeukaryotic communities were classified into 3 groups matching their water mass origins and depth: (1) Group I was in the surface waters of the Bay of Bengal, which had low salinity, and was dominated by Radiolaria Group A, Spirotrichea and marine stramenopiles; (2) Group II was in the DCM within the intrusion of Arabian Sea high salinity water, in which Chloropicophyceae and Pelagophyceae were more abundant; and (3) Group III was located in the 0°-5°S surface water, which was enriched by Dinophyceae. In addition, Caecitellaceae paraparvulus was abundant at 4°S, where weak vertical mixing occurred. This study provides the first baseline of picoeukaryotic diversity in the EEIO.