Physical-chemical influence on taxonomic and functional diversity
To identify key environmental drivers of community taxonomy (at phylum level) and function (SEED level 1), Spearman correlations were calculated; then only significant (p< 0.05) and strong correlations (r > −0.6 or 0.6) were considered. In general, the phyla that positively correlated with temperature were Euryarchaeota, Crenarchaeota, Korarchaeota, Nanoarchaeota, Thermotogae, and Aquificae, whereas several phyla were negatively correlated with temperature (e.g. Acidobacteria, Bacteroidetes, Spirochaetes, Actinobacteria, Verrucumicrobia, Nitrospirae, Deinococcus-Thermus, and Gemmatimonadetes, among others) (Figure 5a). The phyla that negatively correlated with ammonia were Proteobacteria, Thaumarchaeota, Euryarchaeota, and Deferribacteres; those positively correlated were Firmicutes, Acidobacteria, Cyanobacteria, and Spirochaetes, among others. All significant nitrate correlations were positive, including phyla such as Firmicutes, Nitrospirae, Thermotogae, etc. Sulfate showed significant positive correlations with Proteobacteria, Thaumarchaeota, Euryarchaeota, Deferribacteres and Crenarchaeota, and negative correlations with phyla such as Acidobacteria, Cyanobacteria, Actinobacteria, and Verrucomicrobia, among others. Other parameters exhibited positive and negative correlations with several phyla, such as organic matter, organic carbon, B, Cu (uniquely negative correlations), Fe (uniquely negative correlations), Na, K, Ca, Mg and Al (Figure 5a, Supplementary Table 3).
The functional categories (SEED level 1) which presented positive correlations with temperature were “DNA metabolism”, “nucleosides and nucleotides” and “RNA metabolism”, and those which exhibited negative correlations were “fatty acids, lipids and isoprenoids”, “iron acquisition”, “metabolism of aromatic compounds”, “phosphorus metabolism”, “photosynthesis”, “secondary metabolism”, “stress response”, and “sulfur metabolism” (Figure 5b). Ammonia was negatively correlated with functions such as “carbohydrates”, “motility and chemotaxis”, “respiration” and “RNA metabolism”, whereas positive correlations comprised functions as “amino acids and derivatives” and “cofactors, vitamins, prosthetic groups and pigments”. Nitrate also presented negative correlations with “carbohydrates”, “dormancy and sporulation” and “phages, prophages, transposable elements and plasmids”. In contrast, sulfate was positively correlated with “carbohydrates”, “DNA metabolism”, “motility and chemotaxis”, “respiration” and “RNA metabolism”. Other parameters exhibited positive and negative correlations with several functions, such as organic matter, organic carbon, B, Cu, Fe, Si, Na, K, Ca, Mg and Al (Figure 5b, Supplementary Table 3).