The spatiotemporal distribution of haptophytes in the Taiwan Strait: a complex interplay of environmental factors and water mass dynamics

Haptophytes are a group of pico- and nano-sized eukaryotes known for their role in marine ecosystems and biogeochemical cycles, however, their ecology at the species level remains poorly understood for most taxa. This study investigates the spatiotemporal dynamics of haptophytes in the Taiwan Strait, a dynamic conduit between the East and South China Sea characterized by complex hydrography influenced by monsoon patterns. Haptophyte communities were characterized by combining hydrographic measurements with high-throughput sequencing of the 18S rRNA gene V4 region across three campaigns: October–November 2019, May 2020, and August 2020. A total of 82 species belonging to 50 genera were identified, including 28 new records for the East China Sea, and seven species known to form harmful algal blooms. The community structure exhibited significant seasonal variations and differed across distinct water masses, including China Coastal Water, Kuroshio-influenced water, upwelled water, and mixed water. The influence of stochastic processes on community assembly increased from spring to autumn. Chrysochromulina spp. dominated the nutrient-rich coastal water, whereas Gephyrocapsa oceanica/huxleyi prevailed in the warm, oligotrophic water influenced by the Kuroshio Current. This study is crucial for elucidating the ecological roles of haptophytes and their sensitivity and adaptation to climate change and anthropogenic influences.