Effects of Escherichia pollution and salinity on nutrient levels in submerged vegetated wetlands: Insights into benthic community stability and metabolisms.

Inner coastal wetland ecosystems are generally eutrophic and are often exposed to both salinity stress and Escherichia coli pollution. However, the effects of these stressors on nutrient-cycling and microbial communities are under-researched. Here, we established a vegetated wetland ecosystem in a saline environment to understand the effects of E. coli pollution on nutrient removal and benthic microorganisms. The results show that E. coli significantly inhibited nutrient removal, especially total nitrogen (TN) and ammonium (78.89-84.98 and 3.45-44.65% were removed from the non-E. coli-treated and the E. coli-treated water, respectively). Compared with non-vegetated systems, archaeal community variations at both compositional and phylogenetic levels were weakened in vegetated systems (p < 0.05). Among all the environmental factors, the ratios of PO-P to total phosphorus and NO-N to TN contributed the most to archaeal and bacterial community structural variations, respectively. E. coli pollution affected archaeal community succession more than bacteria (p < 0.05). E. coli also weakened the trophic transferring efficiencies between Cyanobacteria and Myxobacteria (p < 0.05). Metabolically, E. coli inhibited bacterial genetic metabolic pathways but made human infection more likely (p < 0.05). Our findings provide new insights into aquatic ecological conservation and environmental management.