Fig. 5: Lake contrasting states found along the transect.

Along the latitudinal transect, freshwater lakes (the typical lake defined for the study region has an average area of 24 ha and a mean depth of 4.0 m – see Supplementary Note 1) range from perennially frozen clear lakes to lakes with seasonal ice cover and high dissolved organic matter content. Lake contrasting states are defined by the duration of ice cover, stratification of the water column and mixing regime, oxygen and light availability, as well as the dissolved organic matter content (given as dissolved organic carbon, or DOC).