Data and study area
Bavaria has a broad variety of lakes, which vary in size, depth, altitude and physiochemical parameters. Information about surface area and maximal lake depth were provided by Bayerisches Landesamt für Wasserwirtschaft (1987). We obtained data for water level statistics from the hydrological service of Bavaria (https://www.gkd.bayern.de/). Physical-chemical data include monthly measurements at the deepest point of the lake. We selected the physical-chemical parameters that were measured for the largest number of lakes. The full list of environmental variables is given in Table 1.
Macrophyte data was also extracted from the Bavarian State Office for the Environment (www.lfu.bayern.de). The macrophyte data were recorded for the EU-Water Framework Directive Monitoring and include vegetation surveys for all large lakes of Bavaria (>0.5 km² surface area) for at least one and maximum five different years. At each lake, macrophyte data for several transects perpendicular to the shoreline at characteristic sections are available (see sampling strategy in Fig. 1a). Each transect is subdivided along the depth gradient into four depths (0-1m; 1-2m; 2-4m; >4m). At each depth all species’ frequency is sampled in five steps following the scale of Kohler (1978), an estimate of abundance.