太湖流域城市湖泊大型底栖动物群落结构及影响因素研究

太湖流域城市湖泊富营养化问题严重，研究不同营养水平城市湖泊底栖动物群落的差异及成因，可为丰富底栖动物生态学研究和城市湖泊生态系统恢复提供参考。本研究于2018年12月、2019年3月、6月、9月在太湖流域15个城市湖泊开展了四个季度的调查，结果显示，重度、中度、轻度富营养和中营养水体分别占10.03%、36.89%、42.07%和11.00%。随水体营养下降，透明度显著上升，浊度、总磷和叶绿素a浓度显著下降，大型底栖动物总生物量、蚌类密度和生物量上升，寡毛类密度和生物量下降。在重度富营养水体中，底栖动物总生物量显著小于其他类型水体（P<0.01）；在轻度富营养和中营养水体中，蚌类密度和生物量显著大于重度和中度富营养水体（P<0.01），寡毛类密度则显著小于重度和中度富营养水体（P<0.01）。Shannon-Wiener、Simpson和Pielou指数随水体营养水平下降，先上升再下降，在轻度富营养水体中最高。结构方程模型分析发现，在轻度富营养和中营养湖泊中，水温、总磷和叶绿素a浓度是影响底栖动物群落的关键环境因子。总磷浓度升高会显著促进软体动物增长（P<0.01），对螺、蚌的路径系数分别高达0.414和0.440。总磷浓度与水温上升都能显著促进多毛类种群增长（P<0.01），抑制水生昆虫种群（P<0.01），路径系数分别为0.376和-0.423。本研究认为，城市湖泊水体中总磷和叶绿素a浓度对大型底栖动物群落结构有重要影响，对磷和藻类的控制，对城市湖泊底栖动物群落恢复和水生态系统修复有重要参考价值。

Community Structure of Macroinvertebrates and Influencing Factors in the Urban Lakes of the Taihu Lake Basin

In the background eutrophication is a very serious problem in urban lakes in Taihu Lake Basin, studies on the causes leading to the differences of macroinvertebrates community under different nutrition levels could enrich the understanding of macroinvertebrates and provide references for the restoration of urban lake ecosystems. In this study, 15 urban lakes in Taihu Lake Basin were selected to survey in December 2018, March, June and September 2019, respectively. Our results showed that heavy, middle, mild eutrophic and mesotrophic water bodies accounted for 10.03%, 36.89%, 42.07% and 11.00%, respectively. With declining of nutrition level, transparency of water body increased, and turbidity, total phosphorus and Chlorophyll a declined. And also, total biomass of macroinvertebrates, the density and biomass of mussels increased, and the density and biomass of Oligochaeta declined. In the heavy eutrophic water bodies, the total biomass of macroinvertebrates were significantly smaller than that in other eutrophic water bodies(P<0.01). In mild eutrophic and mesotrophicwater bodies, the density and biomass of mussels were significantly bigger than that in heavy and middle eutrophic water bodies(P<0.01), while, the density of Oligochaeta was significantly smaller than that in heavy and middle eutrophic water bodies(P<0.01). Shannon-Wiener diversity index, Simpson index and Pielou index increased first and then decreased with the declining of water nutrition level, and reached the maximum value in the mild eutrophic water bodies. We also found that the water temperature, total phosphorus and Chlorophyll a concentration were key ecological factors, which can affect the macroinvertebrates community structure, in mild eutrophic and mesotrophic urban lakes by building structural equation model analysis. In these water bodies, the increase of total phosphorus could significantly increase the population of mollusks (P<0.01), and the path coefficients for snails and mussels were up to 0.414 and 0.440, respectively. Total phosphorus concentration and water temperature could significantly increase the population of polychaete (P<0.01), and significantly decrease the population of aquatic insects (P<0.01), with path Coefficients for polychaete and aquatic insects up to 0.376 and -0.423, respectively. Our study showed that total phosphorus and Chlorophyll a concentrations had important effects on macroinvertebrates community structure in urban lakes, and further indicated that the reducing the phosphorus and algal concentrations in urban lakes would play a key role in the reconstruction of macroinvertebrates community, and also be important for the restoration of aquatic ecology in urban lakes.