Biological denitrification in a macrophytic lake: implications for macrophytes-dominated lake management in the north of China

• Published in: Environmental science and pollution research international Vol. 27; no. 34; pp. 42460 - 42471
• Main Authors: Deng, Huan-guang, Zhang, Ju, Wu, Jin-jia, Yao, Xin, Yang, Li-wei
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-12-2020; Springer Nature B.V
• Subjects: Acetylene; Aquaculture; Aquatic ecosystems; Aquatic plants; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Autumn; Cycles; Denitrification; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Freshwater ecosystems; Freshwater plants; Lake management; Lakes; Load distribution; Macrophytes; Nitrates; Nitrogen; Research Article; Rhizosphere; Sediments; Spring; Spring (season); Summer; Vegetation; Waste Water Technology; Water bodies; Water Management; Water Pollution Control; Winter; China; Denitrification; Cycling rate of nitrate; Sediment; Macrophytic lake; Nitrogen removal capability; Aquatic plants
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-020-10230-3

Denitrification plays an important role in nitrogen (N) removal in freshwater ecosystems. Aquatic plants might have an impact on the sediment denitrification of water body, especially in macrophytes-dominated lake; however, there were different opinions about it. Our hypothesis was that the sediment denitrification rates differ significantly in different vegetation zones and seasons because of direct and indirect effect of the aquatic plants. Therefore, we studied sediment denitrification in Dongping Lake, a typical macrophytes-dominated lake located in the north of China. The acetylene inhibition technique was used to quantify the sediment denitrification rates (DRs) in the
Phragmites communis
(
P
.
communis
) zone, aquaculture zone,
Potamogeton crispus
(
P
.
crispus
) zone and mixed vegetation zone in July (summer), October (autumn), December (winter) of 2015 and March (spring) of 2016. The results showed that the average DRs were significantly higher in the
P
.
communis
zone (69.0 ± 91.6 μmol N m
−2
 h
−1
) than the mixed vegetation zone (8.70 ± 5.44 μmol N m
−2
 h
−1
), and the average DRs represented significant seasonal difference as in the order of winter (74.5 ± 88.3 μmol N m
−2
 h
−1
) > autumn (15.7 ± 18.6 μmol N m
−2
 h
−1
) ≈ summer (10.7 ± 5.90 μmol N m
−2
 h
−1
) > spring (3.85 ± 1.29 μmol N m
−2
 h
−1
). The DRs generally decreased with the increasing of depth; however, significant increase of DRs with depth were found in certain seasons at the vegetated zones except the non-vegetated zone (the aquaculture zone) indicating the possible rhizosphere effect of aquatic plants on denitrification. The higher DRs and cycling rates of nitrate in the
P
.
communis
zone might be related to the larger biomass and oxygen transporting capacity of
P
.
communis
than those of the other aquatic plants. Winter peaks of DRs might be attributed to the higher NO
3
−
load and the absence of the plant uptake. The high cycling rates of nitrate in Dongping Lake indicated an enhanced internal N cycling by aquatic plants. Sediment denitrification could remove about 537.7 t N every year, which was about 26.5% of annual TN loading in Dongping Lake.