Regional Mountain Conference

Lakes Paione Inferiore (PAI) and Paione Superiore (PAS) are two glacial lakes located in the Western Alps, Piedmont Region, Italy, at 2002 and 2269 m a.s.l. respectively. They have been extensively studied since the 1980s within EU-funded research projects on transboundary air pollution and climate change effects on mountain lake ecosystems. Thanks to the pluriannual data available, the lakes have been included in the European Long Term Ecological Research (eLTER) network. Although close each other, and part of a system of three cascading lakes, PAS and PAI differ in their main physico-chemical characteristics, in relation to morphological, geographical and catchment cover features. The two lakes are also subject to different levels of anthropogenic pressure, as the lower lake is more easily accessible, lies along a hiking route connecting other lakes within the valley, and consequently attracts more visitors. Furthermore, PAI has been subjected to repeated fish stocking during the last 40 years, while PAS is relatively more remote and appears to be less impacted. This difference has been confirmed by a recent preliminary investigation into the presence of microplastics (MPs) in the two lakes and their final outlet: MPs abundance and size increased progressively from the upper lake to the outlet, with local activities likely playing a more substantial role in MPs occurrence in PAI and its outlet. Fibers were the dominant type of MPs and the polymers detected were among the most frequently found in remote ecosystems, suggesting outdoor clothing and equipment as the main source. The other anthropogenic pressure, fish stocking in PAI, appears to alter trophic structure and ecosystem functioning, resulting in substantially higher zooplankton abundance and diversity in PAS than in PAI. These examples demonstrate how human activities exert a major effect on mountain lake ecosystems, affecting water quality and biodiversity, and often interacting with other pressures such as long-range atmospheric pollutants and climate change. Proper management of touristic fluxes and activities potentially affecting mountain lakes (hiking, fishing, picnicking) is needed to protect these fragile ecosystems, also through educational and participatory science initiatives.