FIGURE 2.

Boxplots showing alpha diversity indices according to water type and seasonal groupings. Individual data are given by black points, boxplots show the median values (line), interquartile range (box), and range of the data (whiskers). Alpha diversity indices (indicated on the left axis) were calculated as Chao1 (A), Pielou’s index for evenness (B), Shannon’s diversity index (C), and rare biosphere as singletons (SSO) generated after rarefaction (number of OTUs occurring only once in the sample after rarefaction) (D). nOTU and ACE (not shown) followed the same trend as Chao1, and inverse Simpson’s followed the same trend as Shannon’s. The bottom axis indicates the habitat (sediment, river) or water type (water column). A post hoc Dunn’s test was performed on the Kruskal-Wallis test output to test for differences between seasonal groups and water type groups (Supplementary Figures 2, 3 and Supplementary Table 4).