Number of oligotraphentic, mesotraphentic, and eutraphentic species along depth in clear, intermediate, and turbid lakes, divided into observed species richness (a) and potential species richness (b). The lines show the depth diversity gradient of individual lakes and the boxplots their summarised course along depth for the individual species groups. To compare the observed and the potential species distribution within the lake types and the species groups both are plotted against each other (c), thus every point represents a species group within a lake and every line a linear model combining both. The black line would represent a perfect match between potential and observed species richness. All points below that line show a reduced observed richness, while all plants above the line can be seen as an underestimated potential species richness. The R -values give the correlation coefficients within the group.