Fig. 2: Comparison between urea oxidation rates and key AOA ammonia and urea utilization genes in the three different environments.

a Urea oxidation rates as a percent of combined ammonia and urea oxidation rates in the Gulf of Mexico (yellow), the Black Sea (turquoise) and Angola Gyre (dark blue). Percentages (one value per depth) are calculated for all depths from the Gulf of Mexico and the Black Sea and for depths below 80 m in the Angola Gyre. Non-significant rates were set to the respective limit of detection. Error bars represent propagated uncertainties. Boxplots depict the 25–75% quantile range, with the center line depicting the median (50% quantile); whiskers encompass data points within 1.5× the interquartile range. n = number of measurements per region. *** indicates significant difference between regions in two-sided Mann–Whitney–Wilcoxon test. The fraction of urea oxidation rates to combined ammonium + urea oxidation rates in the Angola Gyre is significantly different from the Black Sea (W = 157, P value = 0.0009) and the Gulf of Mexico (W = 74, P value = 0.002). b Urea oxidation rates in incubations without added ammonium compared to urea oxidation rates in incubations with added ammonium in the Gulf of Mexico (yellow), the Black Sea (turquoise) and Angola Gyre (dark blue). Samples where one urea oxidation rate was zero are filled white. Note the difference in scales between panels. Gray dashed lines show the 1:1 ratio. The difference between urea oxidation rates with or without added ammonium was not significant in the Black Sea and in the Angola Gyre (W = 135, P value = 0.56 and W = 42, P value = 0.93, two-sided Mann–Whitney–Wilcoxon test respectively). The urea oxidation rate in the Gulf of Mexico dropped significantly, when additional ammonium was added (W = 74, P value = 0.0032, two-sided Mann-Whitney-Wilcoxon test). Relative abundance (%) of AOA amoA (c) and ureC (d) assigned to Nitrosopelagicus (WCA magenta, WCB rose), Nitrosopumilus (blue) and other Nitrososphaeria (gray) across all metagenome samples in the three environments. All statistical parameters and source data are provided as a Source Data file.