Short-Term Photochemical and Biological Unreactivity of Macrophyte-Derived Dissolved Organic Matter in a Subtropical Shallow Lake

Table 2

Differences between initial condition and exposition (light) or not (dark) of macrophyte-derived DOM to sunlight in unfiltered water (Bulk), filtered water (Bacterial) and Control (HgCl₂) for 120 h under in situ conditions in the southern part of the subtropical shallow lake Mangueira (southern Brazil) tested by one-way ANOVA and Tukey’s test (mean ± standard deviation).

	Experiment
	(I) Bulk			(II) Bacterial			(III) Control
	Initial	Light	Dark	Initial	Light	Dark	Initial	Light	Dark
Bacterial density; (cells 10^6 mL^−1)	0.81 ± 0.16^a	0.76 ± 0.50^a	0.51 ± 0.41^a	1.71 ± 0.31^a	2.65 ± 0.09^b	0.63 ± 0.07^c	1.43 ± 0.13^a	1.03 ± 0.10^a	2.18 ± 0.33^b
Bacterial biovolume; (µm^3)	0.06 ± 0.02^a	0.05 ± 0.01^a	0.05 ± 0.01^a	0.10 ± 0.01^a	0.08 ± 0.01^a	0.06 ± 0.01^a	0.06 ± 0.01^a	0.07 ± 0.02^a	0.07 ± 0.03^a
Bacterial biomass; (ng C mL^−1)	6.5 ± 0.26^a	3.72 ± 2.06^a	3.33 ± 3.20^a	18.64 ± 5.91^a	24.73 ± 2.77^a	4.14 ± 0.45^b	9.57 ± 1.31^a	8.07 ± 1.85^a	16.49 ± 3.57^b
Bacterial production; (µg C L^−1 h^−1)	0.12 ± 0.04^a	0.28 ± 0.24^a	0.15 ± 0.03^a	0.15 ± 0.01^a	0.02 ± 0.02^b	0.14 ± 0.02^a	0.03 ± 0.01^a	0.03 ± 0.02^a	0.77 ± 0.20^b
Bacterial respiration; (µg C L^−1 h^−1)	NA	NA	1.09 ± 0.12^a	NA	NA	2.28 ± 0.88^a	NA	NA	2.14 ± 1.27^a
Bacterial Growth Efficiency	NA	NA	0.11 ± 0.02^a	NA	NA	0.07 ± 0.03^a	NA	NA	0.22 ± 0.12^a
Ciliate density; (×10^4 cells m^−3)	41.4 ± 1.80^a	1.80 ± 3.12^b	15.60 ± 17.8^a	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0
Dissolved Organic Carbon; (mg C L^−1)	18.69 ± 0.87^a	19.46 ± 11.2^a	26.26 ± 7.83^a	25.07 ± 13.6^a	43.58 ± 25.5^a	35.34 ± 20.4^a	20.90 ± 3.54^a	35.75 ± 3.67^a	46.10 ± 17.5^a
Abs430; (Abs 430 nm (×10^−2))	2.51 ± 0.22^a	2.21 ± 0.12^a	2.63 ± 0.19^a	2.69 ± 0.06^a	1.98 ± 0.14^b	2.35 ± 0.20^a	2.44 ± 0.16^ab	1.84 ± 0.35^b	2.71 ± 0.25^a
Abs250 : 365 nm ratio	0.85 ± 0.09^a	0.85 ± 0.02^a	0.85 ± 0.04^a	0.76 ± 0.07^a	0.79 ± 0.18^a	0.87 ± 0.02^a	0.75 ± 0.05^a	0.79 ± 0.25^a	0.87 ± 0.06^a

Significance of one-way ANOVA and Tukey’s a posteriori test at P < 0.05 is indicated with different lowercase superscript letters within each experiment (Initial versus Light versus Dark). The exception is bacterial respiration and growth efficiency, where differences were tested among experiments. NA: not available because respiration was measured in dark bottles. For all variables n = 3 replicates.