Diatom indices reveal water quality patterns in Mediterranean and alpine temporary ponds

Temporary ponds represent highly dynamic freshwater habitats that support unique biological communities and are particularly sensitive to environmental disturbance. Despite their ecological importance, little is known about how protection regimes and human pressures influence the ecological condition of these systems. In this study, diatom-based indices were used to assess water quality in 24 temporary ponds located in two contrasting environments in Central Italy: 12 ponds in Castelporziano (CP, representative of the Mediterranean site), characterized by restricted public access, and 12 ponds on the Campo Imperatore plateau (GS, representative of the Alpine site), which are frequently exposed to tourism and livestock activity. Thirteen diatom indices were calculated to compare ecological conditions between the two systems. Results showed generally higher Specific Pollution Sensitivity Index (IPS) and Eutrophication Pollution Index (EPID) values (better water quality) in CP, while GS ponds displayed markedly lower Trophic Diatom Index (TDI) values, indicating lower trophic conditions but greater ecological variability. Alpine ponds also showed higher SPEAR herbicides index (SPEAR) values, suggesting assemblages dominated by sensitive taxa. These findings highlight how differences in disturbance regimes and protection levels can influence temporary pond ecosystems and water quality, emphasizing the need for targeted management and conservation strategies.