Methane oxidation fueled by algal oxygen production
Methane emissions are strongly reduced in lakes with anoxic bottom waters. But here – contrary to what has previously been assumed – methane removal is not due to archaea or anaerobic bacteria. A new study on Lake Cadagno in Canton Ticino shows that the microorganisms responsible are aerobic proteobacteria. The oxygen they require is produced in situ by photosynthetic algae.
Sampling was performed from a platform on Lake Cadagno in Canton Ticino (southern Switzerland).
Jana Milucka, Max Planck Institute for Marine Microbiology, Bremen
In contrast to oceans, freshwater lakes – and tropical reservoirs – are significant sources of methane emissions. Methane, a greenhouse gas, arises from the degradation of organic material settling on the bottom. Although lakes occupy a much smaller proportion of the Earth’s surface than oceans, they account for a much larger proportion of methane emissions.
Well-mixed lakes, in turn, are the main contributors, while emissions from seasonally or permanently stratified lakes with anoxic bottom waters are greatly reduced. It has been assumed to date that the methane-removing processes occurring in such lakes are the same as those in marine systems. But a new study carried out on Lake Cadagno (Canton Ticino) by researchers from Eawag and the Max Planck Institute for Marine Microbiology (Bremen, Germany) shows that this is not the case.
The scientists demonstrated that methane is almost completely consumed in the anoxic waters of Lake Cadagno, but they did not detect any known anaerobic methane-oxidizing bacteria – or archaea, which are responsible for marine methane oxidation. Instead, water samples collected from a depth of around 12 metres were found to contain abundant aerobic proteobacteria – up to 240,000 cells per millilitre.
“We wondered, of course, how these aerobic bacteria can survive in anoxic waters,” says first author Jana Milucka of the Max Planck Institute for Marine Microbiology. To answer this question, the behaviour of the bacteria was investigated in laboratory experiments: methane oxidation was found to be stimulated only when oxygen was added to the samples incubated in vitro, or when they were exposed to light.
The scientists concluded that the oxygen required by the bacteria is produced by photosynthesis in neighbouring diatoms. Analysis by fluorescence microscopy showed that methane-oxidizing bacteria belonging to the family Methylococcaceae occur in close proximity to diatoms and can thus utilize the oxygen they generate (Fig. 2).
Thanks to the combined activity of bacteria and diatoms, methane is thus consumed in the lake rather than being released into the atmosphere. This type of methane removal has not previously been described in freshwater systems. Project leader Carsten Schubert of Eawag comments: “For lakes with anoxic layers, and also for certain marine zones, it looks as if the textbooks will have to be rewritten.”
Aerobic methane-oxidizing bacteria may play a significant role wherever sufficient light penetrates to anoxic water layers; according to Schubert, this is the case in most Swiss lakes. Similar observations have already been made in Lake Rotsee near Lucerne, in studies not yet published. Research will now focus on deeper lakes, where initial investigations suggest that different processes occur.
CH: Carsten Schubert, Eawag: +41 (0)58 765 2195; email@example.com
D: Marcel Kuypers, Max Plank Institute for Marine Microbiology, Bremen: +49 421 2028 602; firstname.lastname@example.org
or from the press officer
Manfred Schloesser, Max Plank Institute for Marine Microbiology, Bremen: +49 421 2028 704; email@example.com
Methane oxidation coupled to oxygenic photosynthesis in anoxic waters; Jana Milucka, Mathias Kirf, Lu Lu, Andreas Krupke, Phyllis Lam, Sten Littmann, Marcel MM Kuypers and Carsten J Schubert; The ISME Journal (International Society for Microbial Ecology), advance online publication, 13 February 2015; doi:10.1038/ismej.2015.12;
Dr. Manfred Schloesser | Max-Planck-Institut für marine Mikrobiologie
Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft
How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology