These maps are from a recent paper by JF Lapierre et al. that compared the factors that control lake CO2 at the continental scale. He found that the spatial patterns in lake pCO2 driver‐response relationships translated into the formation of spatial clusters of pCO2 “regulation” that are shown in map (e) even though there is little apparent regional pattern in pCO2

This map is from this article by Sarah Collins et al. It clearly shows how spatial patterns in TP and TN alone do not lead to similar patterns in the ratio of TN:TP.  Also, spatial pattern in TN and TP are similar, but not identical and there are some interesting outliers, e.g., Michigan lakes.  See the article for details on

Emi Fergus et al. published a recent paper that describes the complex features of the freshwater landscape. These maps are very compelling in that they show that there are very different patterns between freshwater ABUNDANCE versus CONNECTIVITY. FIGURE DESCRIPTION (Figure and text from Fergus et al. 2017): Freshwater abundance and connectivity maps by system type. Freshwater abundance is quantified as

This is a map of the full spatial extent of the LAGOS-US database that is currently being built by the Continental Limnology Research Team.