Table 2. Spearman's correlation coefficient (r) between gene frequency and three environmental variables.

Genea,b	Parameter
	Dissolved O2	Temperature	Salinity
nxrA (low-affinity type)	−0.42**	−0.50**	−0.30
All nxrA (high-affinity type)c	−0.58***	−0.33*	0.14
HNOB-only nxrA (high-affinity type)d	−0.66***	−0.19	0.17
narG	−0.46**	−0.53***	−0.25
amoA	0.01	−0.57***	0.29

Abbreviations: HNOB, high-affinity nitrite-oxidizing bacteria.

*P<0.05; **P<0.01; ***P<0.001.

^aGene frequencies are based on data presented in Figure 5c.

^bSee Figure 5b for phylogeny of nxrA genes.

^cAlso includes nxrA genes from anaerobic ammonia-oxidizing (anammox) bacteria.

^dExcludes anammox-like nxrA genes.