Intensive efforts have been put on dinoflagellates research globally due to the economic and health issues posed by harmful algal blooms (HABs). The majority of dinoflagellate studies focus on coastal regions, where the impact of HABS on human society is notably significant. Nonetheless, despite their crucial significant roles in ecosystem dynamics, dinoflagellates in the oceanic region have received little research. We conducted the first large-scale investigation of dinoflagellate distribution through the Kuroshio ecosystem using metabarcoding analysis on V4 and V9 regions on 18S rRNA. We also examined the factors that influence the diversity, biogeography, and niche of each species. Depth (i.e., light and nutrient concentration) and water properties (coastal and oceanic waters) distinguish the community structures of dinoflagellates. Trophic strategy (autotrophy, mixotrophy, heterotrophy) is another factor of the vertical distribution and niche of each species. Interestingly, the relative abundance of HAB assemblages was lower at nutrient-rich coastal stations on the continental shelf than oceanic stations influenced by the Kuroshio. This result suggests the role of the Kuroshio transporting HAB species. We will discuss the remaining issues to fully understand the diversity, biogeography, and dynamics of dinoflagellate in marine ecosystems, as well as the role of the Kuroshio in transporting HAB species under global change.

dinoflagellate, Kuroshio, eDNA,niche, HABs (harmful algal bloom)