Methane Production in Oxic Lake Waters Potentially Increases Aquatic Methane Flux to Air

Tang, Kam W.; Mcginnis, Daniel Frank; Ionescu, Danny; Grossart, Hans‐Peter

doi:10.1021/acs.estlett.6b00150

Cited by 132 publications

(141 citation statements)

References 77 publications

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“…Such a decrease cannot be related to exchange with the atmosphere since the atmospheric d 13 C-CH 4 is close to À47‰ (Quay et al, 1999). A possible explanation would be CH 4 production in oxic conditions related to primary production by pathways that remain elusive (Tang et al, 2016) as recently reported in several lakes (Grossart et al, 2011;Bogard et al, 2014;Tang et al, 2014). Such an explanation is consistent with the eutrophic nature of the Dendre Lake and should be further investigated in future.…”

Section: Discussionmentioning

confidence: 57%

Emission and oxidation of methane in a meromictic, eutrophic and temperate lake (Dendre, Belgium)

et al. 2017

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h i g h l i g h t sThe studied lake was meromictic and characterized by high methane, nutrients and sulfate concentrations in the water column. High aerobic and anaerobic methane oxidation rates were observed in the water column, and were dependent on the season. Anaerobic methane oxidation was linked to sulfate reduction, and potentially to nitrate reduction. Despite high methane oxidation rates, methane fluxes to the atmosphere were high. a r t i c l e i n f o a b s t r a c tWe sampled the water column of the Dendre stone pit lake (Belgium) in spring, summer, autumn and winter. Depth profiles of several physico-chemical variables, nutrients, dissolved gases (CO 2 , CH 4 , N 2 O), sulfate, sulfide, iron and manganese concentrations and d 13 C-CH4 were determined. We performed incubation experiments to quantify CH 4 oxidation rates, with a focus on anaerobic CH 4 oxidation (AOM), without and with an inhibitor of sulfate reduction (molybdate). The evolution of nitrate and sulfate concentrations during the incubations was monitored. The water column was anoxic below 20 m throughout the year, and was thermally stratified in summer and autumn. High partial pressure of CO 2 and CH 4 and high concentrations of ammonium and phosphate were observed in anoxic waters. Important nitrous oxide and nitrate concentration maxima were also observed (up to 440 nmol L À1 and 80 mmol L À1 , respectively). Vertical profiles of d 13 C-CH 4 unambiguously showed the occurrence of AOM. Important AOM rates (up to 14 mmol L À1 d À1 ) were observed and often co-occurred with nitrate consumption peaks, suggesting the occurrence of AOM coupled with nitrate reduction. AOM coupled with sulfate reduction also occurred, since AOM rates tended to be lower when molybdate was added. CH 4 oxidation was mostly aerobic (~80% of total oxidation) in spring and winter, and almost exclusively anaerobic in summer and autumn. Despite important CH 4 oxidation rates, the estimated CH 4 fluxes from the water surface to the atmosphere were high (mean of 732 mmol m À2 d À1 in spring, summer and autumn, and up to 12,482 mmol m À2 d À1 in winter).

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Section: Discussionmentioning

confidence: 57%

Emission and oxidation of methane in a meromictic, eutrophic and temperate lake (Dendre, Belgium)

et al. 2017

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“…Wetlands contribute to the creation of large reservoirs of biodiversity, improve the quality of surface water, reduce flood risk associated with extreme rainfall, and supply streams during low water periods (Brinson et al, 1981;Fustec and Lefeuvre, 5 2000; Mitsch and Gosselink, 2015;Reddy and DeLaune, 2008;Turner, 1991;Whiting and Chanton, 2001). They are also the site of production and emission of greenhouse gases (GHG), which depend on many factors, including pH, oxidationreduction conditions, and biogeochemical functioning (Bastviken et al, 2004(Bastviken et al, , 2011Wang et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Biogeochemical diversity and hot moments of GHG emissions from shallow alkaline lakes in the Pantanal of Nhecolândia, Brazil

Barbiéro

Neto

Braz

et al. 2017

Preprint

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Abstract. Nhecolândia is a vast sub-region of the Pantanal wetland in Brazil with great diversity in surface water chemistry evolving in a sodic alkaline pathway under the influence of evaporation. In this region, more than 15,000 shallow lakes are likely to contribute an enormous quantity of greenhouse gas to the atmosphere, but the diversity of the biogeochemical scenarios and their variability in time and space is a major challenge to estimate the regional contribution. In this study, we compiled measurements of the physico-chemical characteristics of water and sediments, gas fluxes in floating chambers, and 25 sedimentation rates to illustrate this diversity. Although these lakes have a similar chemical composition, the results confirm an opposition between the black-water and green-water alkaline lakes, corresponding to distinct biogeochemical functioning.Black-water lakes are CO 2 and CH 4 sources, with fairly constant emissions throughout the seasons. Annual carbon dioxide and methane emissions approach 790 mmol m -2 y -1 and 73 mmol m -2 y -1 , respectively. By contrast, green-water lakes are CO 2 sinks but significant CH 4 sources with fluxes varying significantly throughout the seasons, depending on the 30 development of the cyanobacterial bloom. The results highlight two hot moments for methane emissions. The first one is suspected after the disappearance of the cyanobacterial bloom, which is accompanied by a drop in pH of the upper part of the sediments. The second one is identified when the O 2 -supersaturation is reached under extreme bloom and sunny weather conditions, which provoke an abrupt O 2 purging of the lakes. Taking into account the seasonal variability, annual methane emissions are around 8,850 mmol m -2 y -1 , i.e., much higher than reported in previous studies for alkaline lakes in

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“…reshwater lakes may be responsible for as much as 20% of total annual methane emissions from natural sources (1)(2)(3), and supersaturation of methane in oxic water columns has been observed in many lakes (4)(5)(6)(7)(8). Some surface water methane is produced by methanogenesis in anoxic bottom waters, followed by upward diffusive transport or ebullition (9).…”

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confidence: 99%

“…Aerobic demethylation of organic compounds such as methylphosphonate (MPn) could also contribute to surface water methane release; however, this pathway has been observed only in marine systems (12)(13)(14)(15)(16). Because lakes may release as much methane to the atmosphere as the entire global ocean (8) and since the pathways for surface water methane production are poorly understood (17), a comprehensive characterization of the biological pathways responsible for methane production in these environments is critical to more-accurate predictions of global freshwater methane emissions (8,9,(18)(19)(20)(21).…”

mentioning

confidence: 99%

“…In permanently stratified lakes with deep chemoclines, where the anoxic bottom waters are essentially disconnected from the air-water interface, methane accumulation is more likely to be due to the production of methane in the surface water than to upward diffusion, since the rate of diffusion should be lower than the rate of methane consumption (8,34). Lake Matano, Indonesia, is a deep, permanently stratified, chronically P-limited lake.…”

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confidence: 99%

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Freshwater Bacteria Release Methane as a By-Product of Phosphorus Acquisition

Yao

Henny

Maresca

2016

Appl Environ Microbiol

103

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Freshwater lakes emit large amounts of methane, some of which is produced in oxic surface waters. Two potential pathways for aerobic methane production exist: methanogenesis in oxygenated water, which has been observed in some lakes, and demethylation of small organic molecules. Although methane is produced via demethylation in oxic marine environments, this mechanism of methane release has not yet been demonstrated in freshwater systems. Genes related to the C-P lyase pathway, which cleaves C-P bonds in phosphonate compounds, were found in a metagenomic survey of the surface water of Lake Matano, which is chronically P starved and methane rich. We demonstrate that four bacterial isolates from Lake Matano obtain P from methylphosphonate and release methane and that this activity is repressed by phosphate. We further demonstrate that expression of phnJ, which encodes the enzyme that releases methane, is higher in the presence of methylphosphonate and lower when both methylphosphonate and phosphate are added. This gene is also found in most of the metagenomic data sets from freshwater environments. These experiments link methylphosphonate degradation and methane production with gene expression and phosphate availability in freshwater organisms and suggest that some of the excess methane in the Lake Matano surface water, and in other methane-rich lakes, may be produced by P-starved bacteria. IMPORTANCEMethane is an important greenhouse gas and contributes substantially to global warming. Although freshwater environments are known to release methane into the atmosphere, estimates of the amount of methane emitted by freshwater lakes vary from 8 to 73 Tg per year. Methane emissions are difficult to predict in part because the source of the methane can vary: it is the end product of the energy-conserving pathway in methanogenic archaea, which live predominantly in anoxic sediments or waters but have also been identified in some oxic freshwater environments. More recently, methane release from small organic molecules has been observed in oxic marine environments. Here we show that demethylation of methylphosphonate may also contribute to methane release from lakes and that phosphate can repress this activity. Since lakes are typically phosphorus limited, some methane release in these environments may be a by-product of phosphorus metabolism rather than carbon or energy metabolism. Methane emissions from lakes are currently predicted using primary production, eutrophication status, extent of anoxia, and the shape and size of the lake; to improve prediction of methane emissions, phosphorus availability and sources may also need to be included in these models.

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Methane Production in Oxic Lake Waters Potentially Increases Aquatic Methane Flux to Air

Cited by 132 publications

References 77 publications

Emission and oxidation of methane in a meromictic, eutrophic and temperate lake (Dendre, Belgium)

Emission and oxidation of methane in a meromictic, eutrophic and temperate lake (Dendre, Belgium)

Biogeochemical diversity and hot moments of GHG emissions from shallow alkaline lakes in the Pantanal of Nhecolândia, Brazil

Freshwater Bacteria Release Methane as a By-Product of Phosphorus Acquisition

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