Diversity and abundance of haptophytes in the East China Sea

Abstract

Haptophytes (Prymnesiophytes) are important members of eukaryotic phytoplankton and therefore influence carbon and sulfur cycles in the marine ecosystem. The objective of this study was to investigate the distribution and taxonomic composition of haptophytes in the East China Sea (ECS). Our sampling area covered the ECS continental shelf in the spring and summer of 2009. An abundance of haptophytes was revealed by fluorescent in situ hybridization with an 18S rRNA-specific probe. A haptophyte blooming event reaching 2.2 x 10(4) cells ml(-1) was observed in the Yellow Sea Mixing Water in spring. Phylogenetic analysis of the 18S rRNA gene revealed that the majority of this bloom was composed of Phaeocystis sequences that affiliated with P. jahnii and P. cordata. In contrast, in summer the assemblage composition of haptophytes was dominated by Chrysochromulina, with a maximum abundance of 3.1 x 10(3) cells ml(-1) occurring near the edge of the Changjiang Diluted Water. We also noted a relationship between larger size haptophytes and water eutrophication. The contribution of haptophytes to total nanoflagellate abundance at the ECS surface was 32% in spring and 12% in summer.