Community assembly and network stability of picoeukaryotic plankton communities in the northeast Indian Ocean

Abstract

Picoeukaryotic plankton played as key components of marine microbial communities, and participate in the marine food webs, especially the carbon cycling. Despite their importance, little is known about the mechanisms of assembly and network stability of picoeukaryotic plankton in the ocean along vertical gradients. Here, we obtained new dataset on the dynamics of picoeukaryotic plankton communities in the northeast Indian Ocean with a vertical gradient of 0–2000 m on two cruises. The diversity of picoeukaryotic plankton gradually decreased along the vertical gradient, with photosynthetic plankton mainly distributed in the epipelagic zone and heterotrophs dominating in the mesopelagic zone. Temperature and dissolved oxygen were the main environmental factors affecting the structure of the picoeukaryotic plankton community along the vertical gradient. The community assembly mechanisms also differed among different water layers, with the epipelagic zone dominated by stochastic processes and the mesopelagic zone controlled by deterministic processes, and heterogeneous selection processes were the main drivers shaping the picoeukaryotic plankton community structure. In addition, picoeukaryotic plankton community network stability showed nonlinear changes in vertical gradients, the mesopelagic zone is dominated by deterministic processes and therefore most resistant to environmental disturbances. Our results provide new insights into the plankton ecology of the northeast Indian Ocean and the structure of microbial communities and networks along vertical gradients.