The summer distribution of coccolithophores and its relationship to water masses in the East China Sea

Abstract

Coccolithophores are calcifying phytoplankton belonging to the phylum Haptophyta, and are thought to play an important role in the marine carbon cycle through the production and export of organic carbon and calcite. A quantitative scanning electron microscope study of coccolithophores was conducted to survey the spatial distribution of coccolithophore communities in surface water covering the continental shelf of the East China Sea (ECS) during the summer of 2014. The abundance of haptophytes was also revealed by fluorescence in situ hybridization with an 18S rRNA-specific probe. The abundance of coccolithophores in the surface-water ranged from 3.7 to 82.8 cells mL−1, contributing a mean 7.0 % to haptophyte abundance. Four distinct coccolithophore groups (A, B, C, and D) were categorized based on similarities of the coccolithophore communities among the stations. Group A was located in the north of the ECS in the Yellow Sea Mixed Water area, where coccolithophore abundance was low. Group B was dominated by Gephyrocapsa oceanica and was located in the south of the ECS in the Taiwan Warm Current. Group C represented the inner shelf assemblages, with Emiliania huxleyi as the major dominant species, and was influenced by the Changjiang discharges. Group D represented the Kuroshio assemblages, with communities dominated by E. huxleyi and Umbellosphaera tenuis in the outer shelf region. These results suggest that coccolithophores tend to migrate with the water masses in the ECS during the summer.