Abstract: We investigated the fatty acid composition of phytoplankton and affecting factors with samples collected from three sites in Hongfeng Reservoir, Guiyang. Cyanobacteria dominated the phytoplankton group. Saturated fatty acids (SFA) dominated total fatty acid contents, with low contents of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). With increasing eutrophication level, the contents of SFA increased, and the contents of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) decreased. The composition of fatty acids can be used as indicator of species composition. DHA content was negatively related with cyanobacteria content (R=-0.87, P<0.05,n=6). The content of some PUFAs was positively related with cyanobacteria content (R=0.89,P<0.05, n=6).

Key words: fatty acid, phytoplankton, affecting factor, Hongfeng Reservoir.