Number of observations of the different limitation types in the four lakes.

N: serial+single N limitation; P: serial+single P limitation; Co: independent+simultaneous co-limitation; Primary N: N+independent co-limitation (primary N); Primary P: P+independent co-limitation (primary P); Light: number of experiments showing light limitation; Co light/Nut.: number of co-limitation between light and Nutrients, n: number of experiments. In the columns Light and Co light/Nut. n gives the number of experiments where light limitation was tested.