Macroinvertebrates: a neglected component of Lake Orta

The benthic fauna of L. Orta is one of the lesser-known lake biocenosis. In particular, studies targeting this group were scarce at the turn of the nineteenth century, and referred only to collection points in single microhabitats or to particular groups. It was only in the first half of the XXth century that studies on littoral benthic fauna, as a whole, began. During the biological decline of the lake, which began in 1927, records of clams and chironomids were reported, but it was only in the second half of the century that the presence of a quite diversified littoral community was confirmed. Before the seventies not much information was available on the deepest benthic community while in later years, the first records of amphipods, chironomids, and oligochaetes were found to a depth of about 60 m. During the eighties, a dense oligochaetes population was found in the profundal, while less important changes occurred along the littoral. Research on littoral fauna continued at the beginning of the nineties and the results revealed the positive effects of the recovery intervention from a qualitative point of view, but the diversity of the profundal fauna still remained extremely low. Since the beginning of the XXI century no more information has been available nor projects launched, as a consequence there is an urgent need of more in-depth studies and monitoring programs focusing on the entire lake basin, using standardized methodologies, to support the activities of the Environmental Protection Agencies for the classification of the ecological status of the lake as required by the Water Framework Directive. Moreover, there is a urgent need to program a coring campaign or to use existing cores to obtain data on the past situation of macroinvertebrates in relation to lake acidification through the use of subfossil chironomids., and because Bonacina et al. found sub-fossil cocoons remains of Spirosperma ferox, a species typical of oligotrophic environments, that completely disappeared from the waters of L. Orta a few years after the beginning of the pollution, resurrection ecology techniques could be of help in contributing to the repopulation of the lake through a few original species.