Fig. 5Functional
versus taxonomic groups of microbiota in the water of river ecosystems.
(a) Z-scores achieved by standardization of relative abundances of
functional groups (heatmap) within each functional group (heatmap,
averaged across each functional group). Rank correlations between
environmental variables and relative abundances of functional groups.
Blue and red colors indicate negative and positive correlations,
respectively. *, P < 0.05; **, P <
0.01; and ***, P < 0.001. (b) Key functions of
microbiota under different land-use types.
The functional prediction results showed that the microbial functional
groups in sediment samples were more diverse than those in water
samples. A comparative analysis across the three river areas revealed
numerous microbial function groups associated with N respiration,
nitrate respiration, denitrification, and human pathogens in the
sediment of Weihe River. In addition, there were multiple microbial
function groups associated with fermentation, methanogenesis, aerobic
nitrite oxidation, and human pathogenic gastroenteritis in the sediment
of Hanjiang River. Furthermore, there were some microbial functional
groups associated with aerobic chemoheterotrophy, photoautotrophy, and
intracellular parasites in the sediment of Qinling tributaries (Fig.
S6).
To determine whether the functional groups with differences in
relative abundance could serve as
biomarkers
of
anthropogenic disturbance in freshwater environments, an
LEfSe
analysis was performed at the functional group level (LDA >
2, P < 0.05). N cycling was the main function in the
Weihe River sediment, with denitrification and organic degradation being
the main functions in autumn, and ammonification and metal respiration
being the main functions in spring (Fig. 6a-b). Fermentation and
oxidation-related functions were dominant in the Hanjiang River
sediment. Phototrophy and oxidation were the main functions in the
sediment of Qinling tributaries. Overall, N metabolism was the primary
function in the river areas under different land-use types, and the
relative abundance of microbial functional groups associated with N
metabolism was significantly higher in the sediment of Weihe River than
those in the other areas in autumn (Fig. 6c-d).