Long-term monitoring of community succession in impoundment lake: Responses of macroinvertebrate to South-to-North Water Diversion Project

Abstract The East Route operation of the South-to-North Water Diversion Project (SNWDP) in China provides a unique opportunity to explore the effects of large-scale cross-regional water transfer on the benthic macroinvertebrate community. A five-year biomonitoring campaign was carried out in Nansi Lake, one of the typical impoundment lakes along the East Route of SNWDP. Ten environmental variables and benthic macroinvertebrate samples were collected in order to evaluate the impacts of water diversion project and the resilience of macroinvertebrate community temporally and spatially. Impacts were evaluated by using a newly developed Inter-annual Index based γ-diversity as well as α and β diversity ways. Biological metrics decreased in early disturbed stage and increased in recolonized stage, indicating a general degraded-recovered pattern when community suffering disturbance. Community in lakeside suffered greater impacts at early disturbed stage but with stronger resilience in recolonized stage than that in lake region. Redundancy analysis showed significant correlations between community structure and physicochemical variables such as water depth, transparency and pH in normal status while temperature in recolonized stage. Thus, the impacts of water diversion project on benthic macroinvertebrate were primarily induced by the variation of physical characteristics, especially the life history of benthic macroinvertebrate inhabiting lake shore area. Moreover, values of traditional diversity indices were too low to provide visually acceptable results when assessing the community succession under large temporal and spatial scale background. The newly suggested Inter-annual Index based γ-diversity offered advantages than traditional indices when assessing the interannual succession of benthic community.