Bioindicators in high-mountain lakes of the Alps: A viewpoint on current status and possible future directions

High-mountain lakes in the Alps are unique but highly sensitive ecosystems, characterized by nutrient scarcity, short ice-free periods, and simple food webs. Their remoteness and low local disturbance make them wellrecognized sentinels of global environmental change, yet they are increasingly affected by climate warming, long-range atmospheric deposition, invasive species, and local anthropogenic pressures. Bioindicators represent key tools to assess these dynamics, but their application in Alpine lakes remains fragmented. To evaluate the current state of knowledge, we conducted a Scopus-based literature survey that retrieved 45 eligible studies published between 1997 and 2025. The analysis shows that research has primarily focused on macroinvertebrates, diatoms, and zooplankton, with fewer studies addressing fish, phytoplankton, and amphibians. Most investigations adopted single-taxon approaches, limiting the ability to capture ecosystem complexity and multi-stressor interactions. Moreover, geographic representation was uneven, with Italy and Austria dominating research efforts and other Alpine countries remaining underrepresented. A future shift toward multimetric indices integrating structural and functional indicators across trophic levels is required to achieve more comprehensive ecological assessments. These frameworks should be coupled with chemical monitoring, ecotoxicological bioassays, and emerging tools such as environmental DNA, paleoecological reconstructions, and remote sensing. Standardized protocols, shared databases, and collaborative networks will be essential to overcome current limitations. Advancing toward integrative and harmonized monitoring approaches will ensure that high-mountain lakes continue to function as critical benchmarks of ecological resilience and as earlywarning systems under accelerating global change