Spatiotemporal distribution of their community composition along with seasonally changing surrounding environments especially in coastal region. High-throughput sequencing was conducted for analyzing PCR amplified 18S rRNA gene sequences using Illumina platform to assess protists community compositions. Protists communities were collected onto 0.2µm pore size filter by filtering seawater obtained from 50 m depth at five sites in Wakasa Bay, which is located in the center of the northern coast of Japan Island, over four seasons from 2016 to 2017.