Abstract
Mountain lakes provide a variety of ecosystem services (ES) such as water, habitat, recreation and aesthetic values. However, global change pressures increasingly affect lake ecosystems, necessitating suitable indicators to monitor changes in ES so that targeted protection measures can be developed. Limnological data in ES assessments are mostly limited to transparency for evaluating recreational and aesthetic values, but to date, limnological parameters related to plankton community composition have rarely been associated with ES. This study therefore aims to link limnological parameters to potential ES provision using widely applied standard parameters as well as metabarcoding based on 16S/18S rDNA high-throughput sequencing (HTS) to obtain information on phytoplankton communities. We collected 10 limnological parameters of 26 mountain lakes in the European Alps (1,489 to 2,922 m a.s.L.) and related them to six ES identified by local stakeholders. Our results generally indicate low to moderate concentrations of total phosphorus and chlorophyll a and high Secchi depths. Therefore, the trophic state of the majority of lakes was classified as ultra- (n = 6) or oligotrophic (n = 18), while two lakes were assigned to oligo-mesotrophic conditions. The phytoplankton functional groups were generally in agreement with the trophic state, i.e., we observed a decreasing relative abundance of mixotrophic vs. phototrophic phytoplankton with increasing trophic state. With regard to the ES, our results indicate that most lakes had high potential in providing multiple ES. Only six of the 26 lakes were inhabited by larger cladocerans, indicating reduced food availability for newts and thus less potential for the maintenance of populations and habitats. The high transparency of most lakes indicated a high potential for aesthetic and recreational values, whereas a few lakes with a greater proportion (>30%) of phototrophic phytoplankton manifested reduced water clarity, probably due to eutrophication. Our findings suggest that a deterioration of ecological conditions in mountain lakes may negatively affect future ES provision. Therefore, it will become increasingly important to protect pristine lakes, with data on plankton community composition potentially providing useful guidance for deciding which lakes should receive priority for protection measures.