关键词: 硅藻组合, 总磷重建, 富营养化, 营养物基准, 石塘湖

Abstract: Total phosphorous (TP) concentration is an good indicator of lake eutrophication,and quantitative reconstruction of the history of variation of TP concentration of water in the lake may reveal the history of nutrient evolution of the lake. Based on the high-resolution study of diatom fossil in drill cores of sediments in that lake coupled with the functional model for diatom-TP conversion for lakes in the middle and lower reaches of the Yangtze River,succession of diatom composition in and history of nutrient evolution of the Shitang Lake was quantitatively reconstructed. Results show that diatom flora experienced change from Aulacoseira granulata-dominated composition (prior to 1981) to Aulacoseira alpigae–dominated one (after 1981). Prior to 1981, TP concentration remained around 50 - 60 μg•L^-1, indicating a medium nutrition level, while after 1981, TP concentration increased rapidly to >100μg•L^-1，and the diatom community was dominated by A. alpigae accompanied with an increasing proportion of eutrophy-phil diatoms, such as Cyclotella atomus, Cyclotella meneghiniana, Nitzschia palea, Stephanodiscus hantzschii, which indicated the beginning of eutrophication of the lake. Since the 1980s increasing discharge of domestic sewage, application of chemical fertilizers and expansion of aquaculture have become the major causes of the eutrophication and the change in diatom flora. To a certain extent, the global warming is another contributor. On the basis of the findings, the TP of 60μg•L^-1 is proposed to be the baseline for management of eutrophication of the Shitang Lake. This study also offers reliable reference for setting up targets for management and remediation of the lake and a large number of similar lakes in this area.

Key words: diatom composition, total phosphorous reconstruction, eutrophication, nutrient baseline, Shitang Lake