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

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

研究不同营养水平城市湖泊底栖动物群落的差异及成因,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。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4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%、42.08%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,底栖动物总生物量为(9.57±8.29)g/m^(2),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,分别为1.14±0.04、0.55±0.02、0.68±0.02。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。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,控制磷和藻类,有助于城市湖泊底栖动物群落恢复和水生态系统修复。

Eutrophication is a serious problem in the urban lakes of the Taihu Lake basin. In this study, 15 urban lakes in the basin with varying nutrient levels were studied. The evolution of the macroinvertebrate community in these urban lakes, as well as environmental factors driving change were investigated based on a seasonal survey of macroinvertebrates and the water environment in December 2018, and March, June and September 2019. The aim was to add to our knowledge of macroinvertebrate ecology and provide a reference for ecorestoration of urban lakes. Based on the comprehensive nutrition status index TLI(∑), the 15 urban lakes included heavily(10.3%), moderately(36.89%) and mildly(42.07%) eutrophic, and mesotrophic(11%) water bodies. Among the lakes,differences in water transparency, turbidity, total phosphorus and Chlorophyll a were highly significant(P<0.01), and they were the factors indicating lake trophic status. As nutrient levels decreased,transparency significantly increased, while turbidity,total phosphorus and Chlorophyll a significantly decreased. Total macroinvertebrate biomass, and mussel density and biomass increased as nutrient levels declined, while Oligochaeta density and biomass decreased. In heavily eutrophic water bodies, the total biomass of macroinvertebrates(9.57±8.29) g/m2 was significantly lower than in the less eutrophic lakes(P<0.01). In the mildly eutrophic and mesotrophic lakes, mussel density and biomass were significantly larger than in the heavily and moderately eutrophic lakes(P<0.01), while Oligochaeta density was significantly lower(P<0.01). Shannon-Wiener diversity, Simpson richness and Pielou evenness indices increased, but then decreased as nutrient levels decreased with respective maximum values of(1.14±0.04),(0.55±0.02) and(0.68±0.02) in the mildly eutrophic lakes. After developing a structural equation model, we found that water temperature, total phosphorus and Chlorophyll a were the key environmental factors affecting macroinvertebrate community structure in mildly eutrophic and mesotrophic urban lakes. Further analysis showed that increasing levels of total phosphorus significantly increased mollusk populations(P<0.01), with path coefficients were as high as 0.414 for snails and 0.440 for mussels. Total phosphorus concentration and water temperature significantly increased polychaete populations(P<0.01), and significantly decreased aquatic insect populations(P<0.01), with path coefficients as high as 0.376 for polychaetes and-0.423 for aquatic insects. In a word, total phosphorus and chlorophyll a concentrations had important effects on the macroinvertebrate community structure in urban lakes. Reducing phosphorus levels would reduce algal concentrations in urban lakes and play a key role in restoring the macroinvertebrate community and the aquatic ecology of urban lakes.