雅砻江下游大型底栖无脊椎动物群落结构及与环境因子的关系

Macroinvertebrates community structure in relation to environmental variables in the lower reaches of the Yalong River

为了解雅砻江下游梯级水电开发对底栖动物的群落结构的影响,22个样点的调查分别于2020年春季(5月)和秋季(10月)开展.对不同类型河段(自然河段、坝上库区段和坝下河段)样点的底栖动物群落结构特征及其与环境因子的关系进行分析.结果表明:2020年雅砻江下游共鉴定底栖动物82种(属),优势种为摇蚊属Chironomus sp.和四节蜉属Baetis sp.,与历史研究相比,雅砻江下游在梯级水电开发后,底栖动物优势类群不再包含适应急流生境的类群,仅有适应静缓流的类群.春、秋季的底栖动物现存量和Shannon-Wiener多样性指数在不同河段间(自然河段、坝上库区段和坝下河段)均无显著性差异,春季底栖动物密度显著小于秋季(n=42,P<0.05).PCoA和Adonis配对检验分析表明,空间上,春、秋季的底栖动物群落在自然河段、坝上库区段和坝下河段间均无显著差异;时间上,春、秋季底栖动物群落整体上具有显著性差异(n=42,P<0.01),主要贡献者为摇蚊幼虫.CCA和Envfit拟合分析表明,底栖动物群落在春季的主要影响因子为Chl-a、COD_(Mn);在秋季的主要影响因子为NO_(2)^(-)-N、TN、T、EC.

Surveys with 22 sampling sites were conducted in spring(May)and autumn(October)of 2020 to understand the impact of cascade hydropower development on macroinvertebrate community structure in the lower reaches of the Yalong River.The characteristics of macroinvertebrate community structure and its relationship with environmental variables at different groups of sampling sites(natural river sections,upstream and downstream of the dams)were analyzed.The results showed that a total of 82 macroinvertebrate species(genera)were identified and the dominant species were Chironomus sp.and Baetis sp..In comparison to previous studies,the dominant species were only the species that adapted to static or slow-flowing water,and the species that adapted to fast-flowing water were not dominant anymore since the cascade hydropower development.The densities of macroinvertebrates in spring were significantly lower than those in autumn(n=42,P<0.05).However,no significant difference was found in density,biomass,richness,or the Shannon-Wiener diversity index between spring or autumn and among different groups of sites.PCoA and Adonis paired test analysis showed that there was no significant difference in community structure among sites from natural river sections,upstream of dams and downstream of dams in spring and autumn,respectively.In the temporal domain,the difference in community structure between spring and autumn was significant(n=42,P<0.01),and the main contributor was chironomid larvae.The CCA and Envfit analyses revealed that the main factors influencing the macroinvertebrate community structure in spring were Chl-a and COD_(Mn),and in autumn NO_(2)^(-)-N,TN,T,and EC.