The influence of multiple controls on structural and functional characteristics of macroinvertebrate community in a regulated Alpine river

In the past 30 years several studies have proved that the rivers flow regime is fundamental in structuring biotic communities. The condition of the ecosystem results from the occurrence of extreme events, such as floods and droughts, but also from habitat availability and from its temporal variation. Describe the relationships between macroinvertebrate community characteristics and environmental gradients of flow, temperature, nutrient supplies and habitat conditions is fundamental to understand ecological dynamics. This is the basis for predicting changes within the communities and in ecosystem functions and ultimately to properly manage and conserve the riverine ecosystems. Seven sites, along a 20-km river sector, were surveyed for macroinvertebrates and water chemistry seasonally, from 2012 to 2016. Habitat conditions were assessed along a 500 m stretch in each site. The river discharge was continuously monitored by two water level recorders and used to reconstruct various hydrological indices specific for each sampling location. During the sampling period numerous high flow events and some prolonged periods of low flow were observed. Quantile regression was used to describe the effects of potential limiting factors on macroinvertebrate community which were primarily driven by antecedent flow conditions and season while habitat conditions and water chemistry played only a minor role. Quantitative models have been developed to predict structural and functional characteristics of macroinvertebrate community as a function of antecedent flow conditions, habitat and physico-chemical water characteristics. Those models allow to identify the main drivers and predict the effect of different water management strategies to riverine ecosystem.