The Composition Of Seston Fatty Acids And Structure Of Phytoplankton Communities In Tropical And Subtropical Lakes And Reservoirs

Phytoplankton is the most important component in seston (fine particles in water). Fatty acid, having important physiological function, is an essential biochemical component in the phytoplankton cells. It plays a central role in regulating trophic transfer of energy and biomass within the food web of aquatic ecosystem. As the composition and structure of a phytoplankton community varies over eutrophication, the relationship between trophic states and composition of fatty acids in seston could be useful for understanding of the processes of eutrophication, the effect of eutrophication on ecosystem function and the mechanism of algal blooms.In this research, six reservoirs and two lakes with different trophic status in Guangdong Province were investigated every two months in 2004. According to trophic states, these water bodies were divided into four groups: oligotrophicreservoirs-Xinfengjiang Reservoir and Liuxihe Reservoir, meso-trophic reservoirs-Feilaixia Reservoir and Shenzhen Reservoir, eutrotrophic reservoirs -TangxiReservoir and Qiyeshi Reservoir, and eutrophic shallow Lakes-Zhongxin Lakeand Xiannv Lake (the two sublakes of Xing Lake). In addition, a dinoflagellate bloom was investigated in 2005, in which the water quality variables such as phosphorus concentration and nitrogen concentration, phytoplankton community structure, particle organic carbon and fatty acid composition of phytoplankton were measured. The study focuses on the possible relation between phytoplankton community structure and fatty acid composition over eutrophication processes.In the oligotrophic reservoirs, Cyanophyta, Chlorophyta and Bacillariophyta were dominant in Xinfengjiang Reservoir. The relative abundance of Cyanophyta, Chlorophyta and Bacillariophyta was average in February and October. The abundance of Dinobryon divergens that is rich in polyunsaturated fatty acid was obviously higher in February and October than that in April and June. Thus, the concentration and diversity of fatty acids were high in Xinfengjiang Reservoir in February and October. Bacillariophyta, which is rich in C16:l and EPA, was the main group of phytoplankton in Liuxihe Reservoir. But saturated fatty acid is the main...