TABLE 3.

TEA activities with endogenous substrates in cavity groundwater^a

Groundwater date	Nitrate data		Sulfate data		Methane data
	Initial concn (μM)	Consumption rateb (μmol liter−1 h−1)	Initial concn (μM)	Consumption rate (μmol liter−1 h−1)	Initial concn (μM)	Production rate (μmol liter−1 h−1)
July 2001	NDc	1.18 ± 0.22	51 ± 1.3	−0.03 ± 0.01d	34 ± 8.6	5.5 ± 0.9
December 2001	ND	0.95 ± 0.26	45 ± 0.1	−0.23 ± 0.11	27 ± 5.5	5.8 ± 1.1

^aEach datum value is the mean ± standard deviation (n = 3).

^bNitrate (12 μM) was added prior to measuring the rate.

^cND, not detected (the detection limit was 0.5 μM).

^dThe sulfate concentration was increased.