The observed DDG is clearly hump-shaped for meso- and eutraphentic species across all lake types, whereas oligotraphentic species have a linear DDG in clear and intermediate lakes and are not present in turbid lakes (Figure 2a). The potential depth diversity gradient (DDG) is hump-shaped across all lake types and species groups (Figure 2b). By comparing the observed species richness with the potential species richness for all lake types and species groups (Figure 2c), we find the highest correlations within turbid lakes for meso- (R = 0.71) and eutraphentic species (R = 0.65). Within those lakes, the observed species richness is smaller than the potential species richness (below the line) almost in all lakes and species groups. Intermediate and clear lakes, also contain lakes where observed species richness is higher than the potential species richness (above the line). In intermediate lakes in all species groups observed species richness and potential species richness correlate slightly positive (Figure 2c). In clear lakes, potential species richness correlates negatively with observed species richness for oligo- and mesotraphentic species. The DDG for all individual lakes can be found in the Appendix 2 as in Supporting Information (Figures S2.1-2.10).