TABLE 6.

Proportion of hydrogen utilized for sulfate reduction in Brack Pond sediments incubated at 4°C

Initial H2 level (kPa)	Mean amt (μmol) ± SD ofa:		% H2 used for sulfate reductionb
	H2 utilized	Sulfate reduced
0	0	0.57 ± 0.07	0.0
3	11.69 ± 0.89	1.29 ± 0.04	24.8
6	19.08 ± 0.39	1.04 ± 0.04	9.7
12	19.53 ± 2.89	0.80 ± 0.11	4.7
18	19.78 ± 4.33	0.76 ± 0.21	3.7

^aDetermined after 136 h of incubation in sediments retrieved in 2001. Values are means of at least duplicate determinations ± 1 SD.

^bDetermined according to the equation 4 H₂ + SO₄²⁻ + H⁻ → 4 H₂O + HS⁻.