长江干流宜昌-安庆段大型底栖动物群落结构及环境分析

COMMUNITY STRUCTURE AND ENVIRONMENTAL ANALYSIS OF MACROZOOBENTHOS IN YICHANG-ANQING REACHES OF THE YANGTZE MAINSTEM

为系统了解目前长江中下游干流大型底栖动物群落结构现状,于2016年5—6月和10—12月对长江干流宜昌-安庆段进行2次调查。共记录大型底栖动物96种,水生昆虫种类数最多,占总数的49.0%。大部分物种(58.7%)的出现频率都较低(<1%),且各江段种类组成差异较大。大型底栖动物密度为(213±58) ind./m^2,生物量为(0.202±0.066) g/m^2。大型底栖动物群落结构汛前汛后差异显著,汛后种类数和现存量均明显下降。与建坝前资料相比,大型底栖动物群落结构发生较大改变,种类数增加,现存量下降。环境分析表明影响大型底栖动物分布的主要因素是流速,底质和水质的影响不大。大型底栖动物现存量下降与建坝后干流冲刷加剧有关,针对底栖动物保护,建议开展水沙调节、营造缓流生境并加强洲滩保护。

To systematically understand the community structure of macrozoobethos in the mid-lower Yangtze main- stem, two field investigations were conducted on 13 sections along Yichang-Anqing reaches in May-June and October- December 2016, respectively. A total of 96 taxa of macrozoobenthos were recorded with the most abundant group of aquatic insects that account for 49.0% of the total. The frequency of occurrence was relatively low (<1%) for most species (58.7%), and species composition were obviously different among reaches. The density of macrozoobenthos was (213±58) ind./m^2 , and the biomass was (0.202±0.066) g/m^2 . Community structure was different between pre-flood and post-flood periods, where obvious decreases in both species number and standing crops were found in the latter. Compared with the pre-damming data, community structure of macrozoobenthos had increased species number and decreased standing crops. Environmental analyses showed that velocity was the key factor affecting the distribution of macrozoobenthos, while substrate and water quality parameters were of little importance. The sharp decline in standing crops of macrozoobenthos was closely related to the increased scouring effects in post-damming period. These results suggest to carry out regulation of flow and sediment, to create slow-flow habitats and to strengthen protection of sand bars with regard to macrozoobenthos conservation in the Yangtze mainstem.