Patterns and surrogates of EPT taxa (Ephemeroptera, Plecoptera, Trichoptera) in glacier-fed streams: insights from Western Italian Alps

Alpine streams are highly vulnerable to climate change and are experiencing alterations in average flow, hydrological regimes, and nutrient supply, with multiple implications for freshwater biota. This study examined aquatic macroinvertebrates from three key orders: Ephemeroptera, Plecoptera, and Trichoptera (EPT), which are typical of alpine streams and sensitive to anthropogenic pressures and environmental change. The research investigated richness, composition, and distribution of EPT taxa across glacier-fed stream classes, alongside identifying richness surrogates and indicator taxa. From 2010 to 2022, 102 sites in the Western Italian Alps were sampled and categorised into four classes based on their catchment glacier cover (CGC). Communities belonging to streams most influenced by glacier cover were distinctly well-clustered and associated with higher altitudes and lower temperatures. Results showed increasing Ephemeroptera abundance and decreasing Plecoptera richness as glacial influence declined, while EPT family richness displayed no significant variation among glacial classes. Dictyogenus Klaplek, 1904 (Plecoptera) was associated with streams with higher CGC, whereas the roles of Ephemeroptera and Trichoptera emerged in the other three classes. These findings provide a valuable starting point for better understanding EPT communities as sentinels of global change in alpine stream ecosystems.