Fig. 2: Trends in DO and stratification strength.
a–c, Box plots of long-term trends (≥15 years) of bottom-water DO (a), stratification strength (Δρ) (b) and sediment surface area to water volume ratio (Ased/Vwater) (c) by logarithmic lake surface area class. d, GAM residuals of DO trends as a function of Ased/Vwater, Δρ trends and sampling day-of-year trends. Boxes bound the interquartile range (IQR) (25th to 75th percentile) and whiskers extend to the smaller quantity of data extremes or medians ± 1.5× IQR. Dots and lines mark means and medians, respectively. In a, b and d, open symbols signify means whose 95% CIs include 0. Outliers are shown by grey dots. Distinct letters (top) mark statistically different groups (Padj < 0.05, Conover–Iman tests). Bottom labels show the sample size (number of trend lakes) in each surface area class, which differed per variable depending on data availability.
