Fig. 5: Biomass nifH community in relation to N₂O reduction.

a Biomass incubated for 25 days reduced 76 nmol N₂O-N g⁻¹ (dry weight) on average (n = 40 incubations for biomass enriched with N₂O) with activity peaking before inorganic nitrogen accumulated. Data plotted are means ± s.e. b Redundancy analysis (RDA) revealed positive correlations between the initial rates of N₂O reduction and the relative abundance of 22 nifH OTUs, including 15 Cyanobacterial OTUs and 7 Proteobacterial OTUs (arrows in green). c Heat-map (white to dark red) of the relative abundance of the 22 nifH OTUs (in green), identified in b, in samples (columns, n = 10) in rank order of increasing rate of N₂O reduction. n = 10 in b and c. N₂O reduction is presented as a black arrow in b and as a grey ascending triangle in c.