High diversity of haptophytes in the East China Sea revealed by next-generation sequencing and scanning electron microscopy

Haptophytes are a major marine microbial eukaryote group and play important roles in the marine ecosystem. To explore the phylogenetic diversity in haptophyte communities at high sequencing depths, we performed next-generation sequencing (NGS) to investigate the haptophyte community diversity in the East China Sea (ECS) during the summer of 2013. After clustering at 99% similarity, a total of 159 unique operational taxonomic units were detected. All major haptophyte groups, including several novel environmental lineages, were retrieved in the ECS. Chrysochromulinaceae and Phaeocystales represented the most important components of the haptophyte summer community. Our results indicated the existence of high haptophyte diversity and novel haptophyte lineages in the ECS. A comparison between the results from NGS and scanning electron microscopy (SEM) with respect to species diversity and the proportional abundance of coccolithophores showed that NGS had the power to explore overall community diversity, and SEM was capable of a high level of taxonomic resolution to distinguish closely related species with similar 18S rDNA sequences. The NGS method combined with the SEM method could provide comprehensive information for understanding the abundance and distribution of haptophytes in the ocean.