The community composition of Marine Stramenopiles with spatiotemporal variations in a subtropical Pacific Ocean

Heterotrophic protists are the main predators of picoplankton in microbial food webs and they uptake oxygen for respiration that might potentially affect the cycles of atmospheric gases. So far, Marine Stramenopiles (MASTs) have been known as common heterotrophic protists and they contribute substantially to total protist abundances in the ocean. However, the ecological role of MAST community remains underexplored. It is imperative to understand the extent that environmental variables shape the MASTs community, then food web structure would also change rapidly in response to environmental changes. In this study, MASTs community in the southern East China Sea was revealed by 18S rDNA V4 region by Illumina Miseq sequencing. Based on canonical correspondence analysis, MASTs community was significantly determined by temperature and nitrite concentrations. With respect to the abundances and diversity whinin MASTs, MAST-9 had a high representation in MASTs community in subtropical Pacific Ocean, comparing with other oceanic provinces. Additionally, MAST-9 subclades showed distinct niches partitioning, one was more coastal and one was more oceanic. Combination with previous studies, it states that MAST-9 can be important component in anoxic waters and also in oxygenic water in the Northwestern Pacific. This study provides more insight into the microbial diversity of MASTs varied with spatiotemporal variations along a coastal-oceanic transect in a subtropical ecosystem.