The combination of microscopic and metabarcoding analyses revealed a high diversity of algal bloom species in the Taiwan Strait

The Taiwan Strait is located between Fujian and Taiwan Provinces, China, and is susceptible to various currents and human activities, which result in frequent algal blooms. Surface water samples were collected in the Taiwan Strait in the spring of 2022, and phytoplankton community structure was assessed by both microscopic and metabarcoding analyses. Diatoms dominated in phytoplankton community based on microscopy, while dinoflagellates dominated in the eukaryotic phytoplankton based on metabarcoding. Water temperature was the main environmental factor affecting the phytoplankton community structure. A total of 133 algal bloom (AB) species, including 32 harmful algal bloom (HAB) species, were detected via the combination of both methods. Scrippsiella acuminata and Noctiluca scintillans were the dominant AB species. N. scintillans occurs abundantly in shallow coastal waters with low temperatures, low salinities and high nutrient levels. The distribution of AB species in our study is consistent with historical algal blooms in the Taiwan Strait.