Living coccolithophores in the western Pacific Ocean with mesoscale eddies

Living coccolithophores (LCs) are regarded as a group of calcifiers and play important roles in global carbon cycle. This study used microscopic observations of LCs in the western Pacific Ocean to investigate their community structure and biodiversity, especially to test whether local physical traits (mesoscale eddies) could explain their biogeographic distributions during autumn of 2017. The coccolithophore calcite inventory based on carbon-volume transformation was estimated in this study. A total of 28 taxa of coccospheres and 19 types of coccoliths were identified from 161 samples. Gephyrocapsa oceanica was the most predominant species in all the coccolithophore community, followed by Florisphaera profunda, Emiliania huxleyi, Umbilicosphaera sibogae, Gladiolithus flabellatus and Umbellosphaera tenuis. The abundance of coccospheres and coccoliths ranged from 0 to 26.8×10 3 cells/L and from 0 to 138.5×10 3 coccoliths/L, averaged at 4.2×10 3 cells/L and 10.9×10 3 coccoliths/L, respectively. This study indicated that coccolithophore community in the survey area can be clustered into four groups. Three ecological niches of coccolithophores were characterized by their vertical profiles and multivariate statistical analysis. Coccolithophore abundance and species composition were remarkably different among warm-eddy region, G. oceanica dominated warm-eddy region, while F. profunda dominated warm-eddy and none-eddy region. The average values of estimated particulate inorganic carbon, particulate organic carbon were 0.197 μg/L and 0.140 μg/L, respectively. The current field study widened the dataset of coccolithophores in western Pacific Ocean.