TABLE 5.

Rates of sulfate reduction, methanogenesis, and acetate dissimilation in pond sediments and calculations of the contributions of acetate and hydrogen to methanogenesis and sulfate reduction

Pond	Yr of sampling	Temp (°C)	Rate (nmol · cm−3 day−1) of:			poxc	% Methane accounted for by acetated	% Sulfate reduction accounted for by acetatee
			Sulfate reductiona	Methane productiona	Acetate dissimilationb
Salt	1997	4	160.8 ± 1.2	1.1 ± 0.3	111.2	0.99	100	68
Brack	1997	4	124.0 ± 20.9	3.3 ± 0.6	87.8	0.99	27	70
	2001	−10	7.6 ± 0.5	0.68 ± 0.04	17.1	0.98	50	100
Orange	1999	4	106.9 ± 2.4	35.5 ± 3.9	71.8	0.99	2	66
	1999	4f	145.6 ± 9.8	37.5 ± 4.0	102.4	0.99	2	70
	2001	−10	0.44 ± 0.1	1.70 ± 0.34	16.4	0.92	77	100

^aValues are means of at least duplicate determinations ± 1 SD.

^bDetermined from the slopes of plots (Fig. 2) of log specific radioactivity of acetate (× 2.303) × acetate pool size as previously described (10).

^cObtained by measuring the rate of ¹⁴CH₄ and ¹⁴CO₂ and the calculation ¹⁴CO₂/(¹⁴CO₂ + ¹⁴CH₄). Values are means, and the SD is <0.01.

^dBased on the equation CH₃COO⁻ + H⁺ → CH₄ + CO₂ and determined from (nanomoles of acetate centimeter⁻³ day⁻¹ × [1 − p]/nanomoles of CH₄ centimeter⁻³ day⁻¹) × 100.

^eBased on the equation CH₃COO⁻ + SO₄²⁻ → 2 HCO₃⁻ + HS⁻ and determined from (nanomoles of acetate centimeter⁻³ day^{− 1} × p/nanomoles of sulfate reduced centimeter⁻³ day⁻¹) × 100.

^fFreeze-thaw.