A research team led by the University of Basel and the Université de Montréal examined how the ongoing climate warming affects the “behavior” of lakes. The researchers found out why, in near-bottom waters, lakes may even cool down despite warming at the surface, and what the consequences are for the production and emission of greenhouse gases. The results of the study were published in the most recent edition of the journal Limnology and Oceanography Letters.
Lakes play an important role in the global carbon cycle, acting as large natural bioreactors. The temperature of a lake represents an important constraint on the amount of carbon dioxide and methane it emits into the atmosphere.
It was generally assumed that global warming stimulates microbial respiratory processes and the production of these greenhouse gases, while at the same time reducing the carbon storage in lake sediments. An international research team has now examined these interactions more closely and discovered unexpected effects.
The research project not only targeted the direct effects of global warming, but also the indirect ones. The main focus of the investigations was the water temperature and greenhouse gas production in the deeper parts of the lakes.
“We don’t want to question the fundamentals of thermodynamics. There is no doubt that the rates of respiratory metabolic processes in lakes are generally higher at increased water temperatures,” explains Professor Moritz Lehmann from the Department of Environmental Sciences at the University of Basel. “However, climate change will not cause every lake to warm up everywhere.”
Warming near the surface, cooling near the bottom
Lakes worldwide are warming at the surface. However, they are also losing transparency due to increased algae production and enhanced turbidity of the lake water.
“The surface-water warming and the loss of transparency have the effect that more heat is trapped in the upper layers of the lakes, leaving the deeper waters thermally isolated,” says lead author Dr. Maciej Bartosiewicz from the Department of Environmental Sciences at the University of Basel. “Under some circumstances, this can even lead to the cooling of water masses near the bottom of the lake.”
The subtle cooling slows down respiratory decay processes and carbon dioxide production in the lakes, increasing carbon burial within the sediments. Model simulations suggest that the observed effects are most pertinent to relatively small and shallow lakes, which make up approximately half of the global lake surface.
Less carbon dioxide, more methane
The increased differential warming in lakes has yet another effect: the pronounced thermal stratification entails that the deeper water layers do barely mix and are poorly ventilated, which can lead to prolonged anoxia. Under these oxygen-free conditions, methane production by anaerobic microorganisms is enhanced.
“All in all, global warming increases the greenhouse gas potential of lakes, as expected. However, this has less to do with the warming directly, and more to do with increased oxygen depletion at the bottom of these lakes,” concludes Bartosiewicz.
The study was conducted in collaboration with the Université de Montreal and the Eau Terre Environnement Research Centre at the Institut National de la Recherche Scientifique in Quebec.
Prof. Dr. Moritz Lehmann, Dr. Maciej Bartosiewicz, University of Basel, Department of Environmental Sciences, phone +41 61 207 36 16, email: email@example.com
Bartosiewicz, M., A. Przytulska, J.-F. Lapierre, I. Laurion, M. F. Lehmann and R. Maranger
Hot tops, cold bottoms: Synergistic climate warming and shielding effects increase carbon burial in lakes.
Limnology and Oceanography Letters (2019), doi: 10.1002/lol2.10117
Iris Mickein | Universität Basel
How brain rhythms organize our visual perception
09.09.2019 | Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung
Key enzyme found in plants could guide development of medicines and other products
09.09.2019 | Salk Institute
Researchers from the University of Pennsylvania provide a molecular map of every cell in a developing animal embryo
In a paper in Science this week, Penn researchers report the first detailed molecular characterization of how every cell changes during animal embryonic...
The demand for even higher resolution videos will continue to increase in the coming years. For this reason, the German public service broadcaster WDR and the Fraunhofer Heinrich Hertz Institute HHI will collaborate in the coming months to test the Video Coding possibilities offered by the next international standard VVC/H.266.
VVC/H.266 is the successor standard to HEVC/H.265. The latter is currently the most modern and efficient standard for Video Coding and is used, for example, in...
The recording of images of the human brain and its therapy in neurodegenerative diseases is still a major challenge in current medical research. The so-called blood-brain barrier, a kind of filter system of the body between the blood system and the central nervous system, constrains the supply of drugs or contrast media that would allow therapy and image acquisition. Scientists at the Max Planck Institute for Polymer Research (MPI-P) have now produced tiny diamonds, so-called "nanodiamonds", which could serve as a platform for both the therapy and diagnosis of brain diseases.
The blood-brain barrier is a physiological boundary layer that works highly selectively and thus protects the brain: On the one hand, pathogens or toxins are...
For the first time, a team led by Innsbruck physicist Ben Lanyon has sent a light particle entangled with matter over 50 km of optical fiber. This paves the way for the practical use of quantum networks and sets a milestone for a future quantum internet.
The quantum internet promises absolutely tap-proof communication and powerful distributed sensor networks for new science and technology. However, because...
Since their experimental discovery, magnetic skyrmions - tiny magnetic knots - have moved into the focus of research. Scientists from Hamburg and Kiel have now been able to show that individual magnetic skyrmions with a diameter of only a few nanometres can be stabilised in magnetic metal films even without an external magnetic field. They report on their discovery in the journal Nature Communications.
The existence of magnetic skyrmions as particle-like objects was predicted 30 years ago by theoretical physicists, but could only be proven experimentally in...
04.09.2019 | Event News
29.08.2019 | Event News
16.08.2019 | Event News
09.09.2019 | Trade Fair News
09.09.2019 | Life Sciences
09.09.2019 | Materials Sciences