Enhancing nitrate removal from small wetlands via regulating bacterial-algal symbiosis with macrophyte coverage

• Published in: The Science of the total environment Vol. 951; p. 175745
• Main Authors: Duan, He, Zhang, Liang, Wang, Haodong, Li, Sisi, Li, Xudong, Zhuang, Yanhua
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.11.2024
• Subjects: Ecological stresses; Inhibition; Microorganisms; Mutualism; Nitrogen; Vegetation; Microorganisms; Ecological stresses; Inhibition; Nitrogen; Mutualism; Vegetation
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.175745

With increasing land resource constraints, wetlands, as ecological hotspots, are expected to enhance biogeochemical processes to mitigate nitrogen (N) pollution, particularly nitrate-nitrogen (NO3−-N). However, the interactions among bacteria, algae, and macrophytes in wetlands, which are crucial for N removal, remain largely unknown. This study explored how macrophyte coverage influences bacterial-algal interactions, shifting from mutualism to inhibition, thereby affecting N removal. Moderate coverage enhanced NO3−-N and total nitrogen (TN) removal (P < 0.05), which was correlated with increased microbial abundance (P < 0.05). This may have resulted from moderate algal photosynthesis, reduced physiological stress, and the expansion of ecological niches for microbes. Insufficient coverage promoted algal growth (chlorophyll-a > 31.8 μg·L−1), leading to increased competition for substrates and elevated pH, which further inhibited bacterial activity. Excessive coverage also inhibited bacterial activity by reducing illumination and oxidation-reduction potential. Consequently, insufficient and excessive coverage decreased N removal efficiencies by 2.7–15.7 % (NO3−-N) and 3.7–11.1 % (TN) while increasing methane emission potential by 1.4–6.9 times compared with moderate coverage. These findings offer insights into solving NO3−-N contamination using near-natural methods and balancing the ecological and practical considerations for small wetlands. [Display omitted] •NO3−-N removal efficiency varies significantly under different macrophyte coverage.•Coverage impacts bacterial-algal interactions from mutualism to inhibition.•Excessive or insufficient coverage subjects microbes to higher ecological stress.•Moderate macrophyte coverage has economic and ecological benefits in small wetland.