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 106 mL−1)
0.81 ± 0.16a
0.76 ± 0.50a
0.51 ± 0.41a
1.71 ± 0.31a
2.65 ± 0.09b
0.63 ± 0.07c
1.43 ± 0.13a
1.03 ± 0.10a
2.18 ± 0.33b
Bacterial biovolume (µm3)
0.06 ± 0.02a
0.05 ± 0.01a
0.05 ± 0.01a
0.10 ± 0.01a
0.08 ± 0.01a
0.06 ± 0.01a
0.06 ± 0.01a
0.07 ± 0.02a
0.07 ± 0.03a
Bacterial biomass (ng C mL−1)
6.5 ± 0.26a
3.72 ± 2.06a
3.33 ± 3.20a
18.64 ± 5.91a
24.73 ± 2.77a
4.14 ± 0.45b
9.57 ± 1.31a
8.07 ± 1.85a
16.49 ± 3.57b
Bacterial production (µg C L−1 h−1)
0.12 ± 0.04a
0.28 ± 0.24a
0.15 ± 0.03a
0.15 ± 0.01a
0.02 ± 0.02b
0.14 ± 0.02a
0.03 ± 0.01a
0.03 ± 0.02a
0.77 ± 0.20b
Bacterial respiration (µg C L−1 h−1)
NA
NA
1.09 ± 0.12a
NA
NA
2.28 ± 0.88a
NA
NA
2.14 ± 1.27a
Bacterial Growth Efficiency
NA
NA
0.11 ± 0.02a
NA
NA
0.07 ± 0.03a
NA
NA
0.22 ± 0.12a
Ciliate density (×104 cells m−3)
41.4 ± 1.80a
1.80 ± 3.12b
15.60 ± 17.8a
0 ± 0
0 ± 0
0 ± 0
0 ± 0
0 ± 0
0 ± 0
Dissolved Organic Carbon (mg C L−1)
18.69 ± 0.87a
19.46 ± 11.2a
26.26 ± 7.83a
25.07 ± 13.6a
43.58 ± 25.5a
35.34 ± 20.4a
20.90 ± 3.54a
35.75 ± 3.67a
46.10 ± 17.5a
Abs430 (Abs 430 nm (×10−2))
2.51 ± 0.22a
2.21 ± 0.12a
2.63 ± 0.19a
2.69 ± 0.06a
1.98 ± 0.14b
2.35 ± 0.20a
2.44 ± 0.16ab
1.84 ± 0.35b
2.71 ± 0.25a
Abs250 : 365 nm ratio
0.85 ± 0.09a
0.85 ± 0.02a
0.85 ± 0.04a
0.76 ± 0.07a
0.79 ± 0.18a
0.87 ± 0.02a
0.75 ± 0.05a
0.79 ± 0.25a
0.87 ± 0.06a
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.