城市溪流中径流式低坝对底栖动物群落结构的影响

调查了浙江省安吉县内具径流式低坝的城市溪流(6个样点)和参照溪流(3个样点)的底栖动物群落,目的是了解城市溪流底栖动物群落结构退化规律和径流式低坝(2—3 m)对城市溪流底栖动物群落组成与结构的影响。结果表明,参照样点的底质组成以大石块(35.92%)和卵石(33.66%)为主,城市溪流以砾石为主(57.97%)。城市溪流水温和电导率显著高于参照溪流,TN和TP高于参照溪流。底栖动物总分类单元数和EPT分类单元数显著低于参照溪流。城市溪流河道内水坝上下游之间的流速(P=0.273)和宽深比(P=3.92)无显著差异。坝下游水体中的TP高于坝上游,电导率、溶解氧、pH值和水温在坝上下游之间几乎一致。除BI指数坝下游高于坝上游外,坝上下游间底栖动物总分类单元数、EPT分类单元数以及多样性指数、优势度和均匀度指数没有显著差异。但坝下游的耐污类群比例显著高于坝上游,敏感类群比例则显著低于坝上游。与坝上游相比,坝下游捕食者比例上升和集食者比例下降。NMDS结果进一步表明,城市溪流内水坝的建设导致坝上下游底栖动物群落物种组成明显改变。

The impact of run-of stream dams on benthic macroinvertebrate assemblages in urban streams

The aim of our study was to explore the biological degradation of urban streams and to examine the influence of run-off dams (2-3m) in urban streams on the structure and composition of benthos. Macroinvertebrate assemblages of 9 sites (6 were related to the run-off dams in urban streams and 3 in reference streams) were investigated in Xitiao river catchment, Anji county, Zhejiang province. The results showed that the main substrate composition of reference sites were boulders (35.92%) and cobbles (33.66%), while the urban streams were gravels (57.97%). The water temperature and conductivity were significantly increased and the TN and TP were increased in urban streams comparing to reference streams. Whereas, the total taxa richness and EPT taxa richness was significantly decreased in urban streams. The velocity (p=0.273) and depth/width (p=3.92) between above and below sites of dams did not vary significantly. Dissolved oxygen, pH, water temperature and water conductivity were also very similar between the above and below sites of dams, except the TP was increased below dams. Moreover, the total taxa richness, EPT taxa richness, Shannon diversity index and evenness index of the above sites were also similar to the below sites of dams, except the biotic index was higher in the downstream of dams. However, the ratio of sensitive taxa significantly lower and tolerant taxa markedly higher below dams than above dams, and meanwhile the ratio of predators increased and collector-gatherers decreased of below dams. Furthermore, the non-metric multidimensional scaling demonstrated (NMDS) that the macroinvertebrate community composition varied greatly between above and below the run-off dams in our studied urban streams.