Addressing the ocean methane paradox: the role of microenvironments in oceanic methane production
Lead Research Organisation:
Scottish Association For Marine Science
Department Name: Dunstaffnage Marine Laboratory
Abstract
Why is the world's upper ocean supersaturated with methane? We know that it is, but do not understand why. Evidence shows that a portion of the methane comes from in situ production in oxygenated waters, however that seems to contradict all we know about methanogenesis; a strictly anaerobic process. This phenomenon has been termed the 'oceanic methane paradox'. If, however, there were anaerobic microsites in the upper ocean, then it is entirely possible that methanogenesis could occur within them. We now think that marine zooplankton, their excreted faecal material and other sedimenting particles may provide these anaerobic microsites in pelagic waters. Work conducted by our research group at SAMS supports this hypothesis. We have now clearly identified the presence of methanogens (methane producing microorganisms) within marine zooplankton faecal pellets and sedimenting particles. This, along with data showing that elevated methane concentrations are associated with these sites, has led to greater insights into how this anaerobic process may be actively occurring in pelagic waters. We also know that methanogens can use a range of substrates, including carbon dioxide and formate. However, some of the methanogens we have studied from zooplankton faecal pellets are affiliated with the genus Methanolobus, and are thought to utilize one-carbon (C1)-compounds, including dimethylsulphide (DMS) and methylamines (MAs). Potential sources of these two compounds are dimethylsulphoniopropionate (DMSP) and glycine betaine (GB), which are produced by marine phytoplankton to maintain their osmotic balance in seawater. It is likely that when zooplankton eat phytoplankton they consume at least some of the DMSP or GB, which is then packaged into their faecal pellets. DMSP and GB are thought to be converted into DMS and MAs respectively by microbial activity. Grazing therefore represents a pathway for these C1-compounds to enter into the zooplankton gut and faecal pellets, where they may be substrates for methanogenesis. It is thought that aerosol particles generated from either DMS or MAs may contribute to the pH of natural precipitation and play a role in climate control due to their influence on cloud albedo and reflection of solar radiation. Therefore, zooplankton faecal pellets could be instrumental sites both in the production of a greenhouse gas and the removal of climatic feedback gases, having important consequences for our understanding and modelling of the role the oceans play in climate change. We propose to conduct a multidisciplinary project that will further our understanding of the role of zooplankton, their faecal pellets and sedimenting particles as potential sites of in situ methanogenesis in the water column. Our main purpose is to clarify the role of algal derived compounds in methanogenesis, determine the importance of syntrophic relationships in this process and investigate the use of alternative substrates within these sites. This should enable us to determine the main methanogenic groups responsible for this process and how they are influenced by their environment and other microorganisms. The prerequisites for this work have been demonstrated by the group at SAMS and others. However, much of this work, though exciting, is preliminary and the processes remains poorly understood. Research will be carried out using both state of the art techniques (including real-time PCR, stable isotope probing, stable isotope mass spectrometry, CARD-FISH) and established analytical and microbiological methods (culture & culture independent). In addition, through the work of a tied studentship, we hope to add exciting new aspects to this work including further characterisation of isolated methanogens and an increased understanding of their location using CARD-FISH and confocal microscopy. By combining these areas of research with new methodology we hope to start to unravel the ocean methane paradox.
People |
ORCID iD |
Angela Hatton (Principal Investigator) | |
Mark Hart (Researcher) |
Publications
Uher G
(2017)
Photochemical oxidation of dimethylsulphide to dimethylsulphoxide in estuarine and coastal waters.
in Chemosphere
Obata O
(2020)
Investigating the impact of inoculum source on anaerobic digestion of various species of marine macroalgae
in Algal Research
Hicks N
(2017)
Oxygen dynamics in shelf seas sediments incorporating seasonal variability.
in Biogeochemistry
Green DH
(2011)
Coupling of dimethylsulfide oxidation to biomass production by a marine flavobacterium.
in Applied and environmental microbiology
Ditchfield A
(2012)
Identification of putative methylotrophic and hydrogenotrophic methanogens within sedimenting material and copepod faecal pellets
in Aquatic Microbial Ecology
Burdett H
(2015)
Coralline algae as a globally significant pool of marine dimethylated sulfur
in Global Biogeochemical Cycles
Burdett H
(2012)
The effect of chronic and acute low pH on the intracellular DMSP production and epithelial cell morphology of red coralline algae
in Marine Biology Research
Description | The key finding are that: Viable methanogens are found within anaerobic microsites within the ocean. These methanogens can utilise a range of substrate with high numbers of hydrogenotrophic methanogens present in sedimenting particles and zooplankton faecal pellets However the dominant active pathway is through methylotrophic methanogenesis. |
Exploitation Route | This feeds into the important and controversial question of the potential source of methane in oxygenated waters of the ocean. this is important in terms of how we might generate a balanced methane budget for the oceans and to understand the contribution the marine environment makes to green house gas emissions. |
Sectors | Environment Other |
Description | Carnegie collaborative Research Grant |
Amount | £27,000 (GBP) |
Organisation | Carnegie Trust |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 06/2015 |
End | 06/2017 |
Description | Horizons 2020 |
Amount | € 6,000,000 (EUR) |
Funding ID | 654010 - MacroFuels |
Organisation | European Commission |
Sector | Public |
Country | European Union (EU) |
Start | 01/2016 |
End | 12/2020 |
Description | NERC National facilities innovation awards |
Amount | £7,700 (GBP) |
Funding ID | CEH_L_049_05_2010 |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 07/2010 |
End | 09/2014 |
Description | SAGES Small grant |
Amount | £4,000 (GBP) |
Organisation | Scottish Alliance for Geoscience, Environment and Society (SAGES) |
Sector | Academic/University |
Country | United Kingdom |
Start | 03/2012 |
End | 03/2013 |
Description | SAMS capital scheme |
Amount | £15,000 (GBP) |
Organisation | Scottish Association For Marine Science |
Sector | Academic/University |
Country | United Kingdom |
Start | 05/2015 |
End | 06/2016 |
Description | Schools project |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | Working with local schools we made a giant papermache copepod (marine zooplankton), which was then used with the children to create a anomated video showing kids about the importance of marine food webs Children were excited about marine science, plus the video was taken up by a professoional film maker who has edited and added original music and this will now be released publically to a wider audience |
Year(s) Of Engagement Activity | 2012 |