FIG 2.

Diversity analysis and an ordination plot showing the environmental variables and factors influencing the structure of the anammox community. (a) Box plots represent observed OTUs (richness) and inverse Simpson diversity at anoxic, suboxic, dysoxic, and oxic sites (***, P < 0.01; Wilcoxon test). (b) Distance-based redundancy analysis of the 16S amplicon data from the 60 groundwater samples using a Bray-Curtis dissimilarity matrix between samples based on OTU abundance. Vectors show significant environmental variables (excluding ORP due to missing values), constraining the variability in community composition (P < 0.05). “Ca. Brocadiae” OTUs were added to the ordination using species scores (colored squares), and the 5 OTUs shown are identified to the lowest level of taxonomy (g, genus; f, family; o, order; c, class; p, phylum). Several amplicon sequence variants (ASVs) matched each of the 5 OTUs shown with 99 to 100% identity; OTU75 (9 ASVs), OTU74 (6 ASVs), OTU335 (5 ASVs), OTU363 (6 ASVs), and OTU273 (9 ASVs).