PS 39-64 - Seasonal changes of fish assemblages and phytoplankton community structures in the coastal water of Busan, Korea, analyzed by environmental DNA metabarcoding

Abstract: The coastal water of Busan showed complicated oceanographic characteristics due to the seasonal current changes, the heated effluents from nuclear power plants, the seasonal influx of inland waters, and other anthropogenic impacts. Therefore, fish production along the coast of Busan is highly variable in different seasons, whose reason has not been clearly explained. Here, we analyzed fish assemblages and phytoplankton communities using environmental DNA (eDNA) metabarcoding for three years from June 2020 to November 2022. As a result of eDNA metabarcoding with MiFish universal primer, total 499 fish ASVs and 194 species were respectively obtained. The fish assemblages could be divided into three clades (winter, spring-summer, and 2022 autumn) based on similarity analysis. Engraulis japonicus, Lophius litulon were among the most abundant species in the winter and spring-summer clades while Gadus chalcogrammus, Chelidonichthys spinosus, and Scomberomorus niphonius were dominant species in 2022 autumn clade. Hirundichthys oxycephalus and Platichthys stellatus were the most positively and negatively correlate fish species to temperature. Total 702 phytoplankton ASVs were obtained by metabarcoding with 23S universal primer, which covers 18 phyla and 73 species. The phytoplankton communities were divided into three groups: winter-spring, spring-summer, and summer-autumn, clearly showing the seasonal transition of Micromonas bravo – Eunotia sp. – Synechococcus sp. In order to identify species that are sensitive to changes in water temperature, the Spearman correlation test was used to identify species that show a statistically significant correlation with water temperature. Although we were able to detect seasonal patterns of both fish assemblages and phytoplankton communities, we fail to identify any clear correlations between them and further study should be conducted to determine the fish assemblage in the Busan area.