Global climate change and local factors cause hydrological intermittence in Alpine rivers: what are the impacts on biological communities?

Alpine rivers are considered especially sensitive to climate change effects, because of their sensitivity to hydrological/thermal alterations and their specialised biological communities. In particular, a dramatic but almost neglected aspect of this problem is that Alpine rivers, naturally perennial, have been affected over the last decades by a conspicuous increase in frequency and intensity of droughts. We present here the results of the first sampling year of the PRIN NOACQUA project. In 15 alpine rivers, we have identified a ‘perennial’ reach (called M) that permanently maintains the surface running water and an ‘intermittent’ section (called V), where surface water disappears. In these stations, we investigated the benthic communities (diatoms and macroinvertebrates), allochthonous and autochthonous energy inputs and other environmental parameters. We report here only preliminary results for the benthic macroinvertebrate community analyses. Results of statistical models showed that intermittent reaches are functionally different and characterized by significant lower values of taxonomic richness compared to perennial sites and this is mainly due to the depletion of the most sensitive taxa (EPT taxa), indicating a homogenizing effect on benthic communities. Improving our knowledge on the possible evolution of Alpine lotic ecosystems is crucial, because these environments will be subject to an increasing human pressure under the current climatic scenario.