Fig. 3: Epilithic biofilms are the basis for a ‘green food chain’.

a Abundance of genes involved in energy production (light-harvesting complex, transcriptional regulator for phototrophy, and rhodopsin) and photo-heterotrophic interactions (cobalamin metabolism and tryptophan synthesis), across all prokaryotic phyla are represented in the heatmap. Values indicate the log₁₀ abundance per gene within the phyla. b Largest component of the co-occurrence network between pro- and eukaryotic MAGs. Each node corresponds to a MAG (pro- or eukaryote). Size of the node corresponds to degree centrality and the edges represent the positive coefficients of correlation between each node. Colour of each node represents the phylum annotation. NA: unclassified genus. c Spearman’s correlation analyses of relative abundances of eukaryotic primary producers with the CAZyme abundances. CAZymes include AA auxilliary activities, CBM carbohydrate-binding module, CE carbohydrate esterases, GH glycoside hydrolases, GT glycosyltransferases, PL polysaccharide lyases. FDR-adjusted p values were estimated using the ‘cor.mtest’ function from the corrplot R package and are indicated by *, i.e., *<0.05, **<0.01, ***<0.001. d KEGG orthology (KO) pathways enriched in epilithic biofilms compared to publicly available cryospheric metagenomes were further assessed via KEGGDecoder for pathway completion and are displayed. The completeness of the pathways is indicated in the heatmap, per sample.