Effects of aquatic nitrogen pollution on particle-attached ammonia-oxidizing bacteria in urban freshwater mesocosms

Abstract

Ammonia-oxidizing bacteria (AOB) attached to aquatic particles are important participants in ammonia oxidation within hypereutrophic urban river systems. To explore the effects of aquatic nitrogen pollution on particle-attached AOB in urban river, we utilized laboratory mesocosms to investigate the responses of abundances and community structure of particleattached AOB to ammonium (NH 4 + ) and glycine (C 2 H 5 NO 2 ) amendments. The abundance and community structure of particle-attached AOB were determined with quantitative real-time polymerase chain reaction (qRT-PCR) analysis and high-throughput sequencing based on the AOB amoA gene, respectively. Most of the bacterial amoA sequences from different treatments were affiliated with uncultured Nitrosomonadaceae bacterium, uncultured Nitrosomonadales bacterium, and uncultured Nitrosomonas sp., which are closely associated with organic pollution. The species richness and diversity of particle-attached AOB communities increased with increasing NH 4 + and glycine concentrations. Treatment effects contributed significantly to the variance in particle-attached AOB communities. Although, glycine was completely transformed to ammonium within a few days and ammonium amendments would change the community structure of particle-attached AOB, the effect of glycine on the particle-attached AOB community was regulated by both the resulting ammonium concentration, as well as organic matter availability to the heterotrophic bacteria. Results suggested that high anthropogenic nitrogen loadings appeared to promote higher particle-attached AOB richness and diversity in the hypereutrophic urban river, but the effect of organic nitrogen on the particle-attached AOB community was different from the effect of inorganic nitrogen. This study informs ammonia oxidization mechanisms in the hypereutrophic urban rivers, which contributes to remediation/ restoration strategies.

Water temperature and organic carbon control spatio‐temporal dynamics of particle‐attached and free‐living bacterial communities in a hypereutrophic urban river network

“…Most previous studies concluded that inorganic nitrogen and phosphorus enrichment led to a decrease in bacterial α‐diversity of aquatic ecosystems (Hu et al, 2020; Kiersztyn et al, 2019; Tang et al, 2021). However, our previous study indicated that the species richness and diversity of ammonia‐oxidising bacteria increased with increasing NH 4 + (Cai et al, 2022). In addition to nitrogen and phosphorus, organic carbon is an additional important factor that shapes bacterial α‐diversity (Deng et al, 2018; Jiang et al, 2020).…”

“…Compared to free‐living bacteria, particle‐attached bacteria not only absorb nutrients from water, but also can benefit from the organic compounds and nutrients released from the particles (Cai et al, 2022; Gerba & McLeod, 1976; Tang et al, 2017). Particulate algal biomass can serve as habitat for particle‐attached bacteria (e.g., biofilm communities), as well as a readily available carbon source for bacterial metabolism, often leading to high rates of oxygen consumption (Volkmar & Dahlgren, 2006).…”