Dataset Information

Methane formation in tropical reservoirs predicted from sediment age and nitrogen.

ABSTRACT: Freshwater reservoirs, in particular tropical ones, are an important source of methane (CH₄) to the atmosphere, but current estimates are uncertain. The CH₄ emitted from reservoirs is microbially produced in their sediments, but at present, the rate of CH₄ formation in reservoir sediments cannot be predicted from sediment characteristics, limiting our understanding of reservoir CH₄ emission. Here we show through a long-term incubation experiment that the CH₄ formation rate in sediments of widely different tropical reservoirs can be predicted from sediment age and total nitrogen concentration. CH₄ formation occurs predominantly in sediment layers younger than 6-12?years and beyond these layers sediment organic carbon may be considered effectively buried. Hence mitigating reservoir CH₄ emission via improving nutrient management and thus reducing organic matter supply to sediments is within reach. Our model of sediment CH₄ formation represents a first step towards constraining reservoir CH₄ emission from sediment characteristics.

SUBMITTER: Isidorova A

PROVIDER: S-EPMC6662704 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Methane formation in tropical reservoirs predicted from sediment age and nitrogen.

Isidorova Anastasija A Grasset Charlotte C Mendonça Raquel R Sobek Sebastian S

Scientific reports 20190729 1

Freshwater reservoirs, in particular tropical ones, are an important source of methane (CH4) to the atmosphere, but current estimates are uncertain. The CH4 emitted from reservoirs is microbially produced in their sediments, but at present, the rate of CH4 formation in reservoir sediments cannot be predicted from sediment characteristics, limiting our understanding of reservoir CH4 emission. Here we show through a long-term incubation experiment that t ...[more]

PMID: 31358820

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Project description:Ammonia availability due to chloramination can promote the growth of nitrifying organisms, which can deplete chloramine residuals and result in operational problems for drinking water utilities. In this study, we used a metagenomic approach to determine the identity and functional potential of microorganisms involved in nitrogen biotransformation within chloraminated drinking water reservoirs. Spatial changes in the nitrogen species included an increase in nitrate concentrations accompanied by a decrease in ammonium concentrations with increasing distance from the site of chloramination. This nitrifying activity was likely driven by canonical ammonia-oxidizing bacteria (i.e., Nitrosomonas) and nitrite-oxidizing bacteria (i.e., Nitrospira) as well as by complete-ammonia-oxidizing (i.e., comammox) Nitrospira-like bacteria. Functional annotation was used to evaluate genes associated with nitrogen metabolism, and the community gene catalogue contained mostly genes involved in nitrification, nitrate and nitrite reduction, and nitric oxide reduction. Furthermore, we assembled 47 high-quality metagenome-assembled genomes (MAGs) representing a highly diverse assemblage of bacteria. Of these, five MAGs showed high coverage across all samples, which included two Nitrosomonas, Nitrospira, Sphingomonas, and Rhizobiales-like MAGs. Systematic genome-level analyses of these MAGs in relation to nitrogen metabolism suggest that under ammonia-limited conditions, nitrate may be also reduced back to ammonia for assimilation. Alternatively, nitrate may be reduced to nitric oxide and may potentially play a role in regulating biofilm formation. Overall, this study provides insight into the microbial communities and their nitrogen metabolism and, together with the water chemistry data, improves our understanding of nitrogen biotransformation in chloraminated drinking water distribution systems.IMPORTANCE Chloramines are often used as a secondary disinfectant when free chlorine residuals are difficult to maintain. However, chloramination is often associated with the undesirable effect of nitrification, which results in operational problems for many drinking water utilities. The introduction of ammonia during chloramination provides a potential source of nitrogen either through the addition of excess ammonia or through chloramine decay. This promotes the growth of nitrifying microorganisms and provides a nitrogen source (i.e., nitrate) for the growth for other organisms. While the roles of canonical ammonia-oxidizing and nitrite-oxidizing bacteria in chloraminated drinking water systems have been extensively investigated, those studies have largely adopted a targeted gene-centered approach. Further, little is known about the potential long-term cooccurrence of complete-ammonia-oxidizing (i.e., comammox) bacteria and the potential metabolic synergies of nitrifying organisms with their heterotrophic counterparts that are capable of denitrification and nitrogen assimilation. This study leveraged data obtained for genome-resolved metagenomics over a time series to show that while nitrifying bacteria are dominant and likely to play a major role in nitrification, their cooccurrence with heterotrophic organisms suggests that nitric oxide production and nitrate reduction to ammonia may also occur in chloraminated drinking water systems.

Dataset Information

Methane formation in tropical reservoirs predicted from sediment age and nitrogen.

Publications

Methane formation in tropical reservoirs predicted from sediment age and nitrogen.

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