Marine nanoplanktonic diatoms have been frequently either underestimated or overlooked in phyto-plankton investigations due to their small size (2-20 μm), which allows most of them to pass through a regular phytoplankton net of 70-μm pore size. For nanoplanktonic diatom classification, water samples (each 2000 mL) were collected from several representative sea areas of Chinese coast from May 2002 to May 2006. Pelagodictyon