The Comparative Analysis Of Plankton Ecology And Eutrophication Between Gongping Reservoir And Xinghu Lake

For a long period, the reservoir has been considered as a kind of lake,and the same methods and theory as in lake ecology is adopted to analyze the reservoir ecosystem. However, the reservoir limnology founded 1980's has a distinct view that the reservoir ecosystem can be distinguished from that of the lake ecosystems, but there are very few study cases to confirm the difference between the reservoirs and lakes, especially in the tropical regions. In this paper, we selected a large reservoir -Gongping Reservoir and Xinghu Lake in Guangdong province for a comparative analysis.Water samples were collected from four stations in both Gongping Reservoir and Xinghu Lake, in January March, July, October and December in 2002. The TN, TP, PO4-P, NO3-N, NO2-N, NH4-N and Chla were measured and the plankton species and theirs abundances were identified and counted with microscopy.By the investigation, the characteristic of physical environmental factors, the distributions of nutrient in different station over the sampling time ,the species and abundance of plankton, the dominant species and the diversity index were analyzed. Trophic state as TSI and the others in Gongping Reservoir and Xinghu Lake were evaluated..The main conclusions were summarized as follows:The difference in nutrient loading, hydraulic retention time, the thermal stratification and physical construction for the reservoir and the lake, have a significant impact on the spatial and temporal distribution of the nutrient in the reservoir and the lake. The external input of nutrient is the major nutrient source in Gongping Reservoir, while the internal loading as the major nutrient source in Xinhu Lake. The shorter retention time and the lower Zeu/Zmix ratios are the key factors affecting the dominance of Bacillariophyta-Chlorophyta in Gongping Reservoir, while the longer retention time and the higher Zeu/Zmix ratios resulting in the Cyanophyta predominated in phytoplankton community.The dynamic variety in phytoplankton abundance was influenced by temperature change inGongping Reservoir; while the change in nutrient and temperature influenced significantly the phytoplankton abundance. The abundance of zooplankton is related to their food in Gongping Reservoir and Xinghu Lake.The trophic levels of Gongping Reservoir and Xinghu Lake were evaluated, and the result showed the Xinghu Lake was eutrophic and Gongping Reservoir was mesotrophic. In comparison to the historical data, it was clearly showed the trophic levels and TN/TP ratios increased for both the reservoir and the lake.