Emergent macrophytes act selectively on ammonia-oxidizing bacteria and archaea

Abstract

Ammonia-oxidizing bacteria (AOB) and archaea (AOA) were quantified in the sediments and roots of dominant macrophytes in eight neutral to alkaline coastal wetlands. The AOA dominated in most samples, but the bacterial-to-archaeal amoA gene ratios increased with increasing ammonium levels and pH in the sediments. For all plant species, the ratios increased on the root surface relative to the adjacent bulk sediment. This suggests that root surfaces in these environments provide conditions favoring enrichment of AOB.

Fig 1

Box and whiskers plot of ratios of bacterial amoA versus archaeal amoA gene abundance levels on the root surface (left) of the dominant plant species and in the adjacent bulk sediment (right) in eight coastal wetland lagoons in Spain. The median is represented by the black horizontal line in each box. Boxes cover the 25 and 75% quantiles, and bars show the 10 and 90% quantiles. Outliers are marked as dots. Significant differences between the sediment and rhizosphere are indicated by an asterisk.

Fig 2

Three dimensional scatter plot showing the relationship between the ratio of bacterial amoA versus archaeal amoA gene abundance in the bulk sediment, the sediment pH, and the ammonium concentration in the water column. Samples obtained from low- and high-conductivity waters are indicated by filled and open symbols, respectively.