高坝对乌江下游底栖动物群落结构的影响

摘要

基于2006-2016年近10年的长期监测数据, 对乌江下游两座高坝的修建对底栖动物群落结构的影响效应进行研究.结果表明:大坝蓄水前后底栖动物群落结构发生显著变化, 不同时期的群落结构差异明显.蜉蝣目稚虫对生境的剧烈变动不适应, 软体动物田螺科和觹螺科的一些种类对生境的剧烈扰动较为适应, 生活史较短的机会主义物种在水库淹没区和坝下河段逐渐定殖下来.建坝以及大坝的运行调度对乌江下游底栖动物的群落结构产生了重大影响, 底栖动物群落结构随着时间发生一定程度的演替.在底栖动物所有类群中, 软体动物对栖息地的丧失以及流量的剧烈波动具有较高的耐受性, 水生昆虫相对较不耐受环境的剧烈变化, 而甲壳动物的适应性极强.百分比模式相似性指数 (Percent Model Affinity, PMA) 的变动趋势可有效地反映大坝对底栖动物群落的影响效应, 其均值随离坝距离的增加而呈现逐步增加的趋势, 表明大坝调度对水生态造成的负面影响会随着离坝距离的增加而逐步弱化, 这与河流不连续体理论 (Serial Discontinuity Concept, SDC) 的预测趋势基本一致.根据长期监测成果, 蜉蝣目扁蜉科、四节蜉科、细裳蜉科以及毛翅目纹石蛾科的种群恢复状况以及PMA指数可作为评估大坝不利影响减缓措施效果的依据.%Based on the long-term monitoring data in the lower reaches of Wujiang River during 2006-2016, the effects of two high-head dams on macroinvertebrate communities were explored. Our results showed that the communities changed significantly before and after impoundment. Mayflies could not adapt to the drastic changes in habitats but some taxa from the families Viviparidae and Hydrobiidae could adapt to it. The opportunistic species with short life cycles colonized in the inundation areas of reservoirs and the river reaches below dams. Dam construction and operation had strong impacts on the macroinvertebrate communities, resulting in the community succession at a certain degree. Among the main groups, mollusks and crustaceans were tolerant to the drastic flow fluctuations and the loss of habitat, but aquatic insects were not tolerant to it. Our results showed the change trends of PMA (Percent Model Affinity) could effectively reflect the dam effects on macroinvertebrate communities. The average scores of PMA increased with the distance to dams, suggesting the negative effects induced by dam construction and operation were gradually weaken with the increase of distance, it was consistent with the prediction of serial discontinuity concept (SDC) . According to the longterm monitoring results, the population dynamics and restoration status of the families Heptageniidae, Baetidae, Leptophlebiidae and Hydropsychidae, and the biological index PMA could be used to evaluate the mitigation measures against the adverse effects induced by dam construction and operation in future.