Insight into the nitrogen accumulation in urban center river from functional genes and bacterial community

Abstract

Along with urbanization, the intensified nitrogen pollution in urban rivers and the form of black-odor rivers has become one of the biggest concerns. Better understanding of the nitrogen transformations and microbial mechanisms occurring within urban rivers could help to manage their water quality. In this study, pollution characteristics, potential nitrogen removal rate, composition and function of bacterial community, and abundance of functional genes associated with nitrogen transformation were comparatively investigated in a typical urban river (FC) and a suburban river (LH). Compared with LH, FC was characterized by higher content of nutrients, lower potential nitrogen removal rate and lower abundance of functional genes associated with nitrogen transformation in both overlying water and sediment, especially in summer. Sediment dissolved organic matter characterized by excitation−emission matrix (EEM) showed that FC was more severely polluted by high nitrogen organic matter. Our results revealed that anammox was the main nitrogen removal pathway in both rivers and potential nitrogen removal rates decreased significantly in summer. Bacterial community analysis showed that the benthic communities were more severely influenced by the pollutant than aquatic ones in both rivers. Furthermore, the FC benthic community was dominated by anaerobic respiring, fermentative, sulfate reduction bacteria. Quantitatively, the denitrification rate showed a significant positive correlation with the abundance of denitrification genes, whilst the anammox rate was significantly negatively correlated with bacterial diversity. Meanwhile, NH 4 +-N had a significant negative correlation to both denitrification and anammox in sediment. Taken together, the results indicated that the increased nitrogen pollutants in an urban river altered nitrogen removal pathways and bacterial communities, which could in turn exacerbate the nitrogen pollution to this river.

Water Hyacinth microbiome: metagenomic cues from environment and functionality in urban aquatic bodies

“…Our study observed oxidative phosphorylation (aerobic process) and nitrogen metabolism as the dominant energy metabolism functions, followed by methane, sulphur, and carbon metabolism. The urban aquatic bodies are usually influx by a large amount of nitrogen inputs amid higher anthropogenic activities (Yu et al, 2020). The presence of nitrification genes (amoA, B, C), denitrification genes (nir, nar, nor, nos, nap), and core-forming bacterial groups such as Acetobacteraceae, Bradyrhizobiaceae , and Rhizobiaceae substantiated the higher prevalence of nitrogen metabolism in WH of urban aquatic bodies.…”

Unique microbiome in organic matter–polluted urban rivers

“…Ammonium, as a major form of nitrogen in black‐odorous urban rivers, can be directly discharged or derived from nitrogen‐containing organic matter in untreated sewage. Its co‐occurrence with labile organic matter resulted in an overgrowth of both algae and heterotrophic microorganisms in black‐odorous water and easily confounded the organic matter–triggered water blackening and the N/P‐induced water eutrophication (Cao et al, 2020; Duvert et al, 2019; Liang et al, 2021; Yu et al, 2020). This study provides metadata to clarify the correlation between water blackening and eutrophication, and the two types of water pollution may be interconvertible under certain conditions based on the availability of apoptotic cell‐derived organic matter and N/P nutrients (Liang et al, 2021; Yu et al, 2020).…”

“…Its co‐occurrence with labile organic matter resulted in an overgrowth of both algae and heterotrophic microorganisms in black‐odorous water and easily confounded the organic matter–triggered water blackening and the N/P‐induced water eutrophication (Cao et al, 2020; Duvert et al, 2019; Liang et al, 2021; Yu et al, 2020). This study provides metadata to clarify the correlation between water blackening and eutrophication, and the two types of water pollution may be interconvertible under certain conditions based on the availability of apoptotic cell‐derived organic matter and N/P nutrients (Liang et al, 2021; Yu et al, 2020). Moreover, both organic matter and N/P pollution, as environmental stresses, can destabilize microbial communities by distinctively affecting community richness and negative:positive network cohesion (Hernandez et al, 2021; Liang et al, 2021).…”