The study archives contain the results of sequence processing. These files suffice for reproducing the statistical analysis. Filename Content [sample].emapper.annotations Functional annotations CAT.ORF2LCA_incl_names.txt Taxonomic annotations gene_counts.tsv Gene counts As described in the publication, genes were predicted using Prodigal, and then functionally and taxonomically annotated using eggNOG-mapper 2 and CAT. Reads were aligned to genes using Bowtie 2, and then counted using featureCounts. Free ammonia nitrogen (FAN) concentrations have been included to allow for reproducing the linear regularized regression. These concentrations have been statistically standardized. They are saved in the RDS format, used by R. Detailed sample descriptions can be found in the European Nucleotide Archive under accession number PRJEB91257.