Identification of the ecological preferences of Cyclotella comensis in mountain lakes of the northern European Alps

Planktic diatom ecology in the mountain lakes of the northern European Alps has only been studied sparsely so far. To fill this knowledge gap, the driving parameters of planktic diatom assemblage composition in the euphotic zones of twenty lakes located between 955 and 2,060 m a.s.l. were assessed. The mean August water temperature, concentration of major ions, total phosphorous, and lake physical parameters explained significant amounts of variation within the diatom assemblages, as identified by redundancy analysis and consecutive backward selection. Cyclotella comensis was the most abundant taxon in these oligotrophic (35 mg/L). The results of generalized linear models and generalized additive models further revealed that August surface temperature, thermocline depth, and nitrate-N positively and significantly influenced C. comensis growth. These results shed light on the interplay between physical and chemical parameters as important drivers of C. comensis abundance in temperate mountain lakes. They may aid in the interpretation of past and the prediction of future climate-driven changes in planktic diatom composition in these lakes.