Fig. 1.

Sample collection, treatment, and statistical analysis. a A total of 47 samples were collected from 22 sampling sites classified in 5 ecosystems. b Each sample was processed in duplicate, and for each duplicate, 3 different groups were collected: “All bacteria”, which was filtered directly onto a 0.2 µm filter, “Large bacteria” (red), which was filtered directly onto a 0.4 µm filter, and “Small bacteria” (blue), which was the filtrate from the 0.4 µm filter captured on a 0.2 µm filter. c Each OTU from the community sequencing data were classified into 5 categories based on its appearance in the large and small bacteria group of a filter pair or sample. For all categories, it was permissible that an OTU appeared in both the large and small bacteria groups of a filter pair. Unclassifiable was a catch-all for OTUs not meeting the criteria of the other categories, and eliminated OTUs did not meet abundance cutoffs