The temporal and spatial heterogeneity of phytoplanktons in the Northern South China Sea (NSCS) and its relationship with marine environment were investigated based on the data acquired from the survey on fishery resources and their habitat environment in the South China Sea exclusive economic zone and continental shelf carried out from 1997-2002 (sponsored by the state program of special marine survey

HY126-02). The data were analyzed by using GIS spatial analysis model and mapping techniques. The amount of phytoplanktons in NSCS changed from 0.03 to 4179×10

4

ind/m

3

with an average of 87.2×10

4

ind/m

3

in desceding order of summer

winter

spring and autumn. The phytoplankton density was generally higher in the coast waters than in offshore waters. Areas with high phytoplankton density patched along the coastal waters. The high density patches generally occured in the upwelling areas along NSCS coast

such as the northern and central Beibu Bay

Zhelang

Taiwan Bank and Dianbai-yangjiang area. Patches with high phytoplankton density usually shifted from east to west with seasonal changes of monsoon wind and coast currents.