Diversity and distribution of planktonic protists in the northern South China Sea.

To determine the molecular taxonomic affiliations of small planktonic protists in the northern South China Sea, we constructed phylogenetic trees by correlating the 18S rDNA sequences of known heterotrophic protists with those of unknown protists from four sites. There was a high diversity of these protists in the northern South China Sea that were not sampled by net collection. In addition, we discovered a surprisingly large number of novel radiolarian sequences that showed a unique biogeographic group for this location. Our new data on centrohelids confirmed recent studies showing that representatives of this group live in marine habitats and not only in fresh water. We also report two newly classified eukaryotic lineages (Telonemia and Katablepharidophyta) in the South China Sea for the first time. Furthermore, the phylogenetic relationships showed that the distribution of the novel protists in the northern South China Sea had distinct spatial variation. Our work extends knowledge about the diversity and habitats of planktonic protists in the South China Sea. [ABSTRACT FROM AUTHOR]