Author(s): Riccardo Fornaroli; Silvia Calabrese; Francesca Marazzi; Valeria Mezzanotte
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Abstract: In the last 30 years many studies have shown that the river’s flow regime is fundamental in structuring macroinvertebrate communities, both through extreme events such as floods and droughts but also through the definition of habitat availability and its temporal variation. The definition of the relationships among macroinvertebrate community characteristics and environmental gradients (such as flow and temperature variability, nutrient supplies and local 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 the riverine ecosystems. Seven sites, along a 20 km river sector, were surveyed for macroinvertebrate and water chemistry at approximately 3 months intervals, from June 2012 to September 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 the obtained data were used to reconstruct various hydrological indices specific for each sampling locations. Quantile regression was then used to detect the effects of potential limiting factors on macroinvertebrate community. During the survey large floods and prolonged periods with a fairly constant and low flow occurred. Macroinvertebrate communities were primarily driven by flow history and season while habitat conditions and water chemistry played only a minor role. Moreover, macroinvertebrate communities changed more after floods than after low flow periods and the degree of change was proportional to flood magnitude. Structural indicators respond mainly to hydrology while functional indicators respond only to seasonal changes, highlighting how important is to take into account ecology-based dynamics during decision making processes. In this framework quantitative models have been developed to predict the potential characteristics of macroinvertebrate community as a function of selected environmental variables for management and decision-making processes.
Year: 2018