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 the total proportion area or stream density within the Hydrologic Unit (HU) 12 spatial unit for lakes (a), wetlands (b), and streams (c). Abundance values are binned as quantiles. Freshwater connectivity for lakes (d), wetlands (e), and streams (f) is represented by connectivity cluster groups determined by k‐means cluster group using principal components analysis (PCA) scores from lake, wetland, and stream connectivity metrics at the HU12 spatial scale. Dominated is in reference to where spatial units plotted on the PCA axes using relative proportion connectivity metric values. The solid black line represents the estimated boundary of the Wisconsin glacial period—north of the line is glaciated area and south of the line is unglaciated area.
This figure shows the distribution of the underlying data in Oliver et al 2017 (see below). Interestingly, when you look at all data, it is difficult to discern any patterns. While the study found that on average lakes weren’t changing in chlorophyll, roughly 15% of lakes were either increasing or decreasing in chlorophyll.
This GIF is interesting because it shows how a very well-known limnological relationship (total phosphorus versus chlorophyll concentration) changes at the annual scale across about 20 years. There are plenty of lakes that seem to track that rough 1:1 line, but quite a few that do not and do quite interesting things. The lakes that seem to behave more like ping-pong balls are particularly interesting.
Samantha Oliver made this GIF using data and results from her recent paper in Global Change Biology published in 2017. She also shared her code for the above GIF here; as well as the data that the article is based on. You can read more about this article at this blog and this press release.