Nitrogen Transformations and Diversity of Ammonia-Oxidizing Bacteria in a Desert Ephemeral Stream Receiving Untreated Wastewater

Abstract

Levels of inorganic nitrogen species (ammonia, nitrite, and nitrate), ammonia oxidation potential (AOP), and diversity of ammonia-oxidizing bacteria (AOB) were studied in the sediments of a 50-km-long segment of an ephemeral stream in the Negev desert, receiving untreated wastewater. Water analysis in downstream sampling points showed reductions of 91.7% in biological oxygen demand, 87.7% in chemical oxygen demand, 73.9% in total nitrogen, and 72.8% in total ammonia nitrogen. Significant AOP levels in the sediment were detected mainly in the fall and spring seasons. Denaturing gradient gel electrophoresis of AOB 16S rRNA gene fragments showed that in most sampling points, the streambed was dominated by Nitrosospira cluster 3 strains similar to those dominating the stream bank's soils and sediments in nearby springs. Nitrosomonas strains introduced by discharged wastewater and others dominated some sections of the stream characterized by high organic carbon levels. The results suggest that climatic conditions in the Negev desert select for AOB belonging to Nitrosospira cluster 3, and these conditions dominate the aquatic environment effect along most of the stream sections. In addition, the nitrification-denitrification processes were not sufficient to reduce nitrogen levels in the sediment and prevent the eutrophication of some sections of the stream ecosystem. Thus, the discharge of high nitrogen wastewater into desert streams should be done carefully as it may endanger the already fragile ecosystem.

Response of ammonia-oxidizing archaea and bacteria to long-term industrial effluent-polluted soils, Gujarat, Western India

“…Phylogenetic analysis of bacterial amoA gene sequences suggested that AOB was dominated by Nitrosospira-like sequences, with Nitrosomonas-like sequences minimum. AOB cluster-3 was found in all the samples, which was in consistent with previous reports Shen et al 2008;Angel et al 2010;Liu et al 2010). The presence of Nitrosomonas-like sequences could be possibly due to higher ammonium concentration in R2 and R3 soils (Webster et al 2002).…”

Spatial and temporal diversity and abundance of ammonia oxidizers in semi-arid and arid soils: indications for a differential seasonal effect on archaeal and bacterial ammonia oxidizers

“…; sequences – and ). The results are in line with previous studies showing that cluster 3 of Nitrosospira dominates desert soils (Nejidat, ; Angel et al ., ; Orlando et al ., ). Together, the results suggest that arid conditions have selected for a limited AOB diversity compared with temperate climates (e.g.…”

Impact of overlying water velocity on ammonium uptake by benthic biofilms

“…An initial benthic microbial seed was obtained in March 2009 from the Habsor Stream, Israel (Angel et al ., ). The biofilm was scraped off the stream bed material, mixed into 3 l of mineral nutrient solution, filtered through a 75‐µm mesh to remove large grazers and particles and spread evenly over the flume.…”

“…The major parameters affecting nitrification in stream ecosystems are NH 4 + and oxygen concentrations, concentrations and nature of organic matter, pH, temperature, diversity and abundance of nitrifiers, stream morphology, concentrations of other chemical elements (such as phosphorous) and, of particular relevance to this study, overlying water velocity (Prinčič et al ., ; Butturini et al ., ; Wollheim et al ., ; Kemp and Dodds, ; Webster et al ., ; Gücker and Boëchat, ; Angel et al ., ). The importance of relating NH 4 + uptake processes (assimilation, nitrification and denitrification) to flow conditions derives from the reliance of these processes on the transfer of key solutes from the bulk water to the benthic biofilms.…”