TABLE 2.

Effect of irradiation on bacterial production, respiration, BGE, and carbon utilization (i.e., BCP plus bacterial respiration) in lake water with irradiated and nonirradiated humus incubated for 43 h

Humic isolate no.	Treatment	Avg ± SE value
		Respiration (μg C liter−1 h−1)	BCP (μg C liter−1 h−1)	BGEa (%)	C utilizationa (μg C liter−1 h−1)
3	Dark	7.3 ± 0.1b	2.0 ± 0.4	20.6 ± 2.3b	9.3 ± 0.3b
	UV	9.7 ± 0.4	3.5 ± 0.7	26.2 ± 1.8	13.3 ± 0.4
10	Dark	8.8 ± 0.2b	4.1 ± 0.3b	31.8 ± 0.9	13.0 ± 0.2b
	UV	9.8 ± 0.1	5.1 ± 0.4	33.8 ± 1.1	14.9 ± 0.2
11	Dark	8.0 ± 0.2b	1.7 ± 0.2b	17.6 ± 0.9b	9.7 ± 0.1b
	UV	8.9 ± 0.3	3.3 ± 0.5	26.7 ± 1.0	12.2 ± 0.2
12	Dark	7.4 ± 0.1b	1.9 ± 0.2b	20.1 ± 0.8b	9.2 ± 0.1b
	UV	8.6 ± 0.1	3.6 ± 0.7	28.4 ± 2.0	12.2 ± 0.5
Avg	Dark	7.9 ± 0.4c	2.4 ± 0.6c	22.6 ± 3.2c	10.3 ± 0.9c
	UV	9.3 ± 0.3	3.8 ± 0.4	28.8 ± 1.7	13.1 ± 0.7
Avg enhancement (% relative to dark)		18 ± 5c	71 ± 16c	32 ± 10c	29 ± 6c

^aBGE and carbon utilization are averages of all possible combinations between the independent measurements of respiration and production (i.e., n = 3 for bacterial production and respiration and n = 9 for BGE and carbon utilization). The average percent enhancement was calculated as [(irradiated−dark)/dark] × 100 ± standard error (n = 4). The numerical identification of the humic isolates is given in Table 1.

^bIndicates statistically significant differences between dark and UV treatments (t test for BCP and respiration and U test for BGE and carbon utilization, P < 0.05).

^cIndicates statically significant differences in average values and enhancement (paired t test, P < 0.05).