Review: mountain lakes as freshwater resources at risk from chemical pollution

Abstract Background Chemical pollution forms a severe threat for human and environmental health. While the risks for European lowland water bodies are well known, there is little knowledge on remote aquatic ecosystems and particularly mountain lakes, despite their importance for the provision of freshwater. Here, we critically review the current knowledge on the exposure and risk by chemical pollution for mountain lakes and present a tiered approach on how to advance effectively our understanding in the future. Results Generally, pollutant monitoring data are currently incomplete, with many regions and substances having been only poorly investigated. More reliable data exist only for persistent organic pollutants (POPs). However, there is increasing evidence that even remote mountain lakes are exposed to a wide range of organic pollutants. Among them potent pesticides currently used in agricultural and biocidal applications, such as diazinon and permethrin. The exposure of mountain lakes to pollutants follows a complex pattern. Pollutants are introduced into mountain lakes via the atmospheric deposition and run-off from the watershed, but also local sources, like tourism and pastoralism. Our risk assessment and recent biomonitoring studies suggest that there are widespread chronic toxic risks on crustacean in mountain ranges. If mountain ranges are exposed to tourism and pastoralism, even acute toxic effects on crustacean are possible. Thereby, the vulnerability of mountain lakes to toxic effects has to be expected to be particularly high due to the harsh environmental conditions at high altitudes, the organism’s traits, the insular position of mountain lakes and a lower species richness with increasing altitudes. Furthermore, there is little knowledge on the biological processes leading to the degradation of chemical pollutants under the environmental and ecological conditions of mountain ecosystems. Conclusion While the exposure and sensitivity of mountain aquatic ecosystems is currently poorly investigated, the existing data suggest that it is very likely that also water bodies as remote as mountain lakes do suffer from pollution-induced toxicity. To verify this suggestion and expand the existing knowledge, it is necessary that future studies combine a more holistic pollution monitoring with exposure modelling and links to biological effects. Only then will it be possible to obtain a more reliable understanding of the impact of chemical pollution on aquatic mountain ecosystems and to protect these fragile ecosystems