Vertical distribution and community composition of anammox bacteria in sediments of a eutrophic shallow lake

Aims: The aim of this study was to explore the vertical distribution traits of anaerobic ammonium-oxidizing (anammox) bacterial relative abundance and community composition along the oxic/anoxic sediment profiles in a shallow lake.

Methods and results: The Illumina Miseq-based sequencing and quantitative polymerase chain reactions were utilized to analyse relative abundance of anammox hydrazine synthase (hzsB) gene in comparison with bacterial 16S rRNA genes, anammox bacterial relative abundance (the number of anammox sequences divided by total number of sequences), community composition and diversity in sediments. The relative abundance of hzsB gene at the low-nitrogen (LN) site in the lake sediments showed that the vertical distribution of anammox bacteria increased to a peak, then decreased with increasing depth. Moreover, the relative abundance of hzsB gene at the high-nitrogen site was significantly lower than that at the LN site. Additionally, the community composition results showed that Candidatus Brocadia sp. was the dominant genus. In addition, the anammox bacterial diversity was also site specific. Redundancy analysis showed that the total N and the NH₄⁺ -N content might be the most important factors affecting anammox bacterial community composition in the studied sites.

Conclusions: The results revealed the specific vertical variance of anammox bacterial distribution and community composition in oxic/anoxic sediments of a eutrophic shallow lake.

Significance and impact of the study: This is the first study to demonstrate that anammox bacteria displayed the particular distribution in freshwater sediments, which implied a strong response to the anthropogenic eutrophication.