长江支流桥边河大型底栖动物群落结构及水质生物评价

中小河流数量众多，分布广泛，其健康状况将直接影响和决定着大江大河的生态系统健康，如何准确、合理的评估中小河流的健康状况，已经成为世界性的科学问题.本研究以长江一级支流桥边河为例，于2019年1月（枯水期）和8月（丰水期）在河道的上中下游设置8个采样点，进行桥边河大型底栖动物群落结构调查，利用Shannon-Wiener多样性指数、耐污值法和科级生物指数法（FBI）分别对各样点进行水质生物评价.调查结果显示，枯水期采集到底栖动物17个分类单元，共283个底栖动物；丰水期采集到16个分类单元，共301个底栖动物，丰水期大型底栖动物个体数略高于枯水期.水质生物评价结果显示，桥边河水质状况时空差异性明显，丰水期的水质状况优于枯水期，空间尺度上丰枯水期水质状况均为上游段 > 中游段 > 下游段.3种水质生物评价法对比分析显示，FBI科级生物指数的评价结果与实际情况更吻合，更适合桥边河水质评价，其研究结果可为中小河流生态系统健康评价提供参考.

Community structure of macroinvertebrates and water quality bioassessment in Qiaobian River, a tributary of Yangtze River

The health of small-medium river ecosystems is threatened by increasing hydropower development and human activities. It is therefore important to properly diagnose river health. In this study, Qiaobian River, a tributary of the Yangtze River was chosen as the study site. To evaluate its health status we investigated the spatial and temporal variability of macroinvertebrate community structure of the river. Samples were collected from 8 sites that were evenly distributed along the river during January 2019 (low flow season) and August 2019 (high flow season). At each site, the community structure of macroinvertebrates was studied and health status was evaluated using Shannon-Wiener index, Tolerance index and FBI index respectively. In total, 283 macroinvertebrates (17 taxa) were collected in dry season; and 301 macroinvertebrates(16 taxa) were collected in wet season with a slightly higher abundance. The health status of the river was spatially heterogeneous with the apparently better upstream than the downstream. In general, the river health was improved during high flow season compared to the low flow season. Among the three applied methods, a better consistency was found between FBI index and the results provided by Yichang Environmental Protection Agency, suggesting a better applicability of this method in evaluating the health of small-medium rivers. This study provides the first results on diagnosis of health of small-medium rivers by comparing three different bio-assessment methods and will provide new insights for future river health assessments.