Spring macroinvertebrates as potential indicators of ice meltwater within mountain periglacial landforms

Abstract

Periglacial landforms able to hold permafrost or seasonal ice are key elements for high mountain hydrological dynamics, which support societies in arid-semiarid regions and for aquatic biodiversity adapted to low water temperatures. However, the detection of potential internal permafrost still represents a challenge, mainly in regions with limited economic resources, like Southern South America. In Argentina, periglacial landforms containing permafrost are protected under national environmental legis- lation, as they are considered strategic water reserves, although this legal framework is currently under discussion. In the pres- ent study, we surveyed macroinvertebrates and physicochemical variables in 17 springs originating from periglacial landforms (classified into: rock glaciers, solifluction lobes, and debris slopes) located in the alpine zone of four Patagonia Andes mountains (above 1500 m a.s.l.). In our first hypothesis (H1), we tested if springs from periglacial landforms control water quality and aquatic macroinvertebrate diversity, while in our second hypothesis (H2), we evaluated the performance of freshwater macroinverte- brate communities as cost-effective bioindicators of ice meltwater within periglacial landform (intact or relict landforms) and their water quality. We found that periglacial landform type was a weak predictor of springs water quality and macroinvertebrate composition. In contrast, when we classified springs based on macroinvertebrate assemblages (biotic classification), we detected a potential altitude line (1819 m a.s.l.) splitting two main groups of springs, regardless of landform type. Moreover, springs located at higher elevations, characterized by specific Plecoptera, Trichoptera, and Diptera compositions, released water temperatures indicative of potential ice meltwater from permafrost or seasonal ice (values <4°C). In the context of regional climate change, characterized by rising temperatures and declining precipitation, the altitudinal limit of permafrost is expected to shift upward in the coming decades, and such changes could be efficiently monitored through macroinvertebrate assemblages.