Table 2.

Spearman’s rank correlations between the average gas concentrations (n = 52) and stable isotopic values (n = 39) of CH₄ and CO₂, water column depth, temperature, the O₂ concentration, pH (n = 52), and the concentrations of DOC (n = 23), NO_x⁻, NH₄⁺, SO₄²⁻ (n = 39) and Fe³⁺ (n = 13)

	CH4 −concentration	CO2 concentration	δ13C-CH4	δ13C-DIC
Depth	− 0.490**	0.884**	n.s	− 0.872**
Temperature	0.638**	− 0.839**	− 0.332*	0.927**
O2	n.s	− 0.776**	n.s	0.975**
pH	0.625**	− 0.773**	− 0.347*	0.813**
DOC	n.s	n.s	− 0.444*	n.s
NOx−	− 0.403*	0.519**	n.s	− 0.494**
NH4+	0.396*	n.s	n.s	n.s
SO42−	− 0.330*	0.705**	0.351*	− 0.652**
Fe3+	n.s	0.863**	n.s	− 0.802**
CH4		− 0.462**	− 0.726**	n.s
CO2	− 0.462**		n.s	− 0.946**

^*Correlation is significant at the p < 0.05 level (2-tailed)

^**Correlation is significant at the p < 0.01 level (2-tailed)