Fig. 2: Potential N₂ production rates in sediments from various environments and nitrogen loss gene patterns in cold-seep sediments.

a Potential N₂ production rates (denitrification, n = 681; anammox, n = 648) and the percentage of N₂ production attributed to anammox (ra, %; n = 698) across various environments, measured via slurry incubations with nitrogen isotope tracing. DEN and ANA represent denitrification and anammox rates respectively. Environmental differences were computed using two-sided Kruskal-Wallis rank-sum tests; non-seeps vs. cold seeps were compared using a two-sided student’s t test (**: P < 0.01). Data are presented as mean ± SD. b Potential N₂ production rates and ra in non-seep (n = 34) and cold seep (n = 60) measured in this study. Differences were computed using a two-sided student’s t test (***: P < 0.001; ****: P < 0.0001). Boxplot: center line, median; box limits, upper and lower quartiles; whiskers, 1.5 × interquartile range; points, outliers. c Relative abundance (GPM) of nosZ, nod, hzsA, nifH, reductive dsrA, and oxidative mcrA genes in sediment metagenomes (n = 163). Inserted plots highlight genes: all nosZ genes (dark blue), nosZ Clade I genes (orange), nosZ Clade II genes (green), nod genes (dark red), hzsA genes (dark purple), nifH genes (brown), reductive dsrA genes (pink), oxidative mcrA genes (dark yellow). Differences were computed using Kruskal-Wallis rank-sum tests. Data are presented as mean ± SD. d Expression (TPM) of nosZ, nod, hzsA, and nifH genes in sediment metatranscriptomes (n = 33). Inserted plots show the transcriptional abundance of nitrogen loss genes, with differences computed using Kruskal-Wallis rank-sum tests. Data are presented as mean ± SD. e Relationships between gene abundance (GPM) of nosZ, nod, hzsA, and depths (cmbsf) in cold seeps. Average abundance per sample is shown, with regression lines and R values. Source data are provided as a Source Data file.