The Biogeochemical Methane Cycle

AbstractAerobic methane-oxidizing bacteria, or methanotrophs, play a crucial role in the global methane cycle. Their methane oxidation activity in various environmental settings has a great mitigation effect on global climate change. Alphaproteobacterial methanotrophs were among the first to be taxonomically characterized, nowadays unified in the Methylocystaceae and Beijerinckiaceae families. Originally thought to have an obligate growth requirement for methane and related one-carbon compounds as a source of carbon and energy, it was later shown that various alphaproteobacterial methanotrophs are facultative, able to grow on multi-carbon compounds such as acetate. Most recently, we expanded our knowledge of the metabolic versatility of alphaproteobacterial methanotrophs. We showed that Methylocystis sp. strain SC2 has the capacity for mixotrophic growth on H2 and CH4. This mini-review will summarize the change in perception from the long-held paradigm of obligate methanotrophy to today’s recognition of alphaproteobacterial methanotrophs as having both facultative and mixotrophic capabilities.

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Simulating idealized Dansgaard-Oeschger events and their potential impacts on the global methane cycle

Quaternary Science Reviews ◽

10.1016/j.quascirev.2011.08.012 ◽

2011 ◽

Vol 30 (23-24) ◽

pp. 3258-3268 ◽

Cited By ~ 31

Author(s):

Peter O. Hopcroft ◽

Paul J. Valdes ◽

David J. Beerling

Keyword(s):

Methane Cycle

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Methane gas emissions from savanna fires: What analysis of local burning regimes in a working West African landscape tell us

10.5194/bg-2020-476 ◽

2021 ◽

Author(s):

Paul Laris ◽

Moussa Koné ◽

Fadiala Dembélé ◽

Lilian Yang ◽

Rebecca Jacobs

Keyword(s):

Ambient Air ◽

Methane Emissions ◽

Dry Season ◽

West African ◽

Biomass Composition ◽

Fire Intensity ◽

Methane Cycle ◽

Gas Emissions ◽

Savanna Fires ◽

Fire Type

Abstract. Savanna fires contribute significantly to greenhouse gas emissions. While it is recognized that these fires play an important role in the global methane cycle, there are too few accurate estimates of emissions from West Africa, the continent's most active fire region. Most estimates of methane emissions contain high levels of uncertainty because they are based on generalizations of diverse landscapes that are burned by complex fire regimes. To improve estimates we used an approach grounded in the burning practices of people who set fires to working landscapes. We conducted 97 experimental fires collecting data for savanna type, grass type, biomass composition and amount consumed, scorch height, speed of fire front, fire type and ambient air conditions for two sites in Mali. We collected smoke samples for 36 fires using a canister method. We report values for fire intensity, combustion completeness, patchiness, modified combustion efficiency (MCE) and emission factor (EF). Our study finds that methane EFs ranged from 3.71 g/kg in the early dry season (EDS) to 2.86 in the mid-dry season (MDS). We found head fires had nearly double the CH4 EF of backfires (4.89 g/kg to 2.92). Fires during the MDS have the lowest intensity values and the lowest methane emissions 0.981 g/m2 compared with 1.030 g/m2 for EDS and 1.102 g/m2 for the late dry season (LDS). We conclude that policies aimed at shifting the burning regime earlier to reduce methane emissions will not have the desired effects, especially if fire type is not considered. We recommend using the adjusted mean value of 0.862 g/m2—based on the carbon content for West African grasses—for calculating emissions for West African savannas.

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Riddles in the cold: Antarctic endemism and microbial succession impact methane cycling in the Southern Ocean

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.1134 ◽

2020 ◽

Vol 287 (1931) ◽

pp. 20201134 ◽

Cited By ~ 2

Author(s):

Andrew R. Thurber ◽

Sarah Seabrook ◽

Rory M. Welsh

Keyword(s):

Microbial Community ◽

Greenhouse Gas Emission ◽

Ross Sea ◽

Methane Flux ◽

Rrna Gene ◽

Methane Seep ◽

Microbial Succession ◽

Methane Cycle ◽

16S Rrna Gene Analysis ◽

Successional Stage

Antarctica is estimated to contain as much as a quarter of earth's marine methane, however we have not discovered an active Antarctic methane seep limiting our understanding of the methane cycle. In 2011, an expansive (70 m × 1 m) microbial mat formed at 10 m water depth in the Ross Sea, Antarctica which we identify here to be a high latitude hydrogen sulfide and methane seep. Through 16S rRNA gene analysis on samples collected 1 year and 5 years after the methane seep formed, we identify the taxa involved in the Antarctic methane cycle and quantify the response rate of the microbial community to a novel input of methane. One year after the seep formed, ANaerobic MEthane oxidizing archaea (ANME), the dominant sink of methane globally, were absent. Five years later, ANME were found to make up to 4% of the microbial community, however the dominant member of this group observed (ANME-1) were unexpected considering the cold temperature (−1.8°C) and high sulfate concentrations (greater than 24 mM) present at this site. Additionally, the microbial community had not yet formed a sufficient filter to mitigate the release of methane from the sediment; methane flux from the sediment was still significant at 3.1 mmol CH 4 m −2 d −1 . We hypothesize that this 5 year time point represents an early successional stage of the microbiota in response to methane input. This study provides the first report of the evolution of a seep system from a non-seep environment, and reveals that the rate of microbial succession may have an unrealized impact on greenhouse gas emission from marine methane reservoirs.

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Bacterial Processes of the Methane Cycle in Bottom Sediments of Lake Baikal

Microbiology ◽

10.1023/b:mici.0000023990.71983.c1 ◽

2004 ◽

Vol 73 (2) ◽

pp. 202-210 ◽

Cited By ~ 8

Author(s):

O. P. Dagurova ◽

B. B. Namsaraev ◽

L. P. Kozyreva ◽

T. I. Zemskaya ◽

L. E. Dulov

Keyword(s):

Lake Baikal ◽

Bottom Sediments ◽

Methane Cycle

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The methane cycle in the epilimnion of Lake Constance

Fundamental and Applied Limnology / Archiv für Hydrobiologie ◽

10.1127/archiv-hydrobiol/151/2001/157 ◽

2001 ◽

Vol 151 (1) ◽

pp. 157-176 ◽

Cited By ~ 29

Author(s):

M. Schulz ◽

E. Faber ◽

A. Hollerbach ◽

H. G. Schröder ◽

H. Güde

Keyword(s):

Lake Constance ◽

Methane Cycle

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Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements

10.5194/acp-2017-169 ◽

2017 ◽

Cited By ~ 1

Author(s):

Thibaud Thonat ◽

Marielle Saunois ◽

Philippe Bousquet ◽

Isabelle Pison ◽

Zeli Tan ◽

...

Keyword(s):

Land Surface ◽

Transport Model ◽

Land Surface Model ◽

Arctic Region ◽

The Arctic ◽

Surface Model ◽

Multiple Sources ◽

Atmospheric Measurements ◽

Methane Cycle ◽

Methane Budget

Abstract. Understanding the recent evolution of methane emissions in the Arctic is necessary to interpret the global methane cycle. Emissions are affected by significant uncertainties and are sensitive to climate change, leading to potential feedbacks. A polar version of the CHIMERE chemistry-transport model is used to simulate the evolution of tropospheric methane in the Arctic during 2012, including all known regional anthropogenic and natural sources. CHIMERE simulations are compared to atmospheric continuous observations at six measurement sites in the Arctic region. In winter, the Arctic is dominated by anthropogenic emissions; emissions from continental seepages and oceans, including from the East Siberian Arctic Shelf, can contribute significantly in more limited areas. In summer, emissions from wetland and freshwater sources dominate across the whole region. The model is able to reproduce the seasonality and synoptic variations of methane measured at the different sites. We find that all methane sources significantly affect the measurements at all stations at least at the synoptic scale, except for biomass burning; this indicates the relevance of continuous observations to gain a mechanistic understanding of Arctic methane sources. Sensitivity tests reveal that the choice of the land surface model used to prescribe wetland emissions can be critical in correctly representing methane concentrations. Also testing different freshwater emission inventories leads to large differences in modelled methane. Attempts to include methane sinks (OH oxidation and soil uptake) reduced the model bias relative to observed atmospheric CH4. The study illustrates how multiple sources, having different spatiotemporal dynamics and magnitudes, jointly influence the overall Arctic methane budget, and highlights ways towards further improved assessments.

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The methane cycle in ferruginous Lake Matano

Geobiology ◽

10.1111/j.1472-4669.2010.00257.x ◽

2010 ◽

Vol 9 (1) ◽

pp. 61-78 ◽

Cited By ~ 127

Author(s):

S. A. CROWE ◽

S. KATSEV ◽

K. LESLIE ◽

A. STURM ◽

C. MAGEN ◽

...

Keyword(s):

Methane Cycle ◽

Lake Matano

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Outreach and disseminations activities in North Slope of Alaska: how to build trust between local communities and arctic researchers

10.5194/egusphere-egu2020-17963 ◽

2020 ◽

Author(s):

Kaare Sikuaq Erickson ◽

Donatella Zona ◽

Marco Montemayor ◽

Walter Oechel ◽

Terenzio Zenone

Keyword(s):

Common Ground ◽

Local Community ◽

Local Communities ◽

The Arctic ◽

North Slope ◽

Science Fair ◽

Methane Cycle ◽

The North ◽

North Slope Of Alaska ◽

The University

The Alaskan Ukpea&#289;vik I&#241;upiat Corporation (UIC) is promoting and financilally supporting, with the contribution of the US National Science Foundation (NSF) and local organizations,&#160;outreach and dissemination events, in the form of science fair for the local communities in North Slope of Alaska. The science fair is part of a larger effort by UIC Science to bring coordination and collaboration to science outreach and engagement efforts across Arctic Alaska. The purpose is to provide a positive space for Arctic researchers and Arctic residents to meet, eat with each other, spend time, and to inspire the youth of the Arctic by providing fun and educational activities that are based in science and traditional knowledge. The Science Fair 2019 hosted by the Barrow Arctic Research Center (BARC) included three days of youth and family-friendly activities related to &#8220;Inupiat Knowledge about Plants&#8221; led by the College Inupiat Studies Department, &#8220;Eco-chains Activity&#8221; hosted by the North Slope Borough Office of Emergency Management, &#8220;Big Little World: Bugs Plants, and Microscopes&#8221; hosted by the National Ecological Observatory Network, &#8220;Microplastics in the Arctic&#8221; hosted by the North Slope Borough Department of Wildlife Management, &#8220;BARC Scavenger Hunt&#8221; hosted by UIC Science, &#8220;Our Role in the Carbon and Methane Cycle&#8221; hosted by the University of Texas El Paso (UTEP) and San Diego State University, and &#8220;How Permafrost Works&#8221; hosted by the University of Alaska, Fairbanks, Geophysical Institute. Each day hundreds of students, from both the local community and the science community came together to take part in mutually beneficial engagement: students from Utqia&#289;vik were excited about science and now know of the realistic and fulfilling careers in research that takes place in their backyard. The Utqia&#289;vik community members and elders now have a better idea of the breadth of research that takes place in and near their home. The locals, especially the elders, are very concerned about the drastic changes in our environment: scientists share these concerns, and the discussions during the fair was a chance to recognize this common ground. Breaking the ice between Arctic researchers and residents can lead to endless opportunities for collaboration, sharing ideas, and even lifelong friendships.&#160;&#160;

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