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The “methane paradox” in Lake Lugano - understanding methane production in oxygenated waters of lacustrine environments

English title The “methane paradox” in Lake Lugano - understanding methane production in oxygenated waters of lacustrine environments
Applicant Lehmann Moritz
Number 169552
Funding scheme Project funding (Div. I-III)
Research institution Institut für Umweltgeowissenschaften Universität Basel
Institution of higher education University of Basel - BS
Main discipline Hydrology, Limnology, Glaciology
Start/End 01.01.2017 - 30.06.2020
Approved amount 349'959.00
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All Disciplines (2)

Discipline
Hydrology, Limnology, Glaciology
Geochemistry

Keywords (11)

methane paradox; methane oxidation; stable isotope probing; biomarker; dimethylsulphoniopropionate; methane production; zooplankton; methanogenesis; lakes; carbon isotope fractionation; phytoplankton community structures

Lay Summary (German)

Lead
Das “Methan Paradoxon” - Methanproduktion unter aeroben Verhältnissen in Seen
Lay summary

Methan (CH4) ist ein potentes Treibhausgas, welches in grossen Mengen in Feuchtgebieten und Seen produziert wird. Das Projekt untersucht Faktoren, welche das Gleichgewicht zwischen Methanbildung und –verbrauch durch Mikroorganismen in Seen, und damit die Emissionen von CH4 an die Atmosphäre regulieren. Vor allem zielt das Projekt darauf ab, das sogenannte “Methan Paradoxon” zu untersuchen. Dieses Paradoxon beschreibt die Ansammlung von CH4 (welche normalerweise nur unter sauerstofffreien Bedingungen zu beobachten ist) in aeroben Bereichen aquatischer Systeme. Eine biologische Quelle ist wahrscheinlich, aber die Mechanismen der aeroben CH4 -Bildung in Seen sind unbekannt. Das Projekt untersucht die „aerobe“ CH4 -Bildung im Zusammenhang mit 1) Phytoplanktonproduktivität, 2) Methanogenese in Partikelaggregaten, in welchen sich anaerobe Mikromilieus ausbilden können, 3) Methanogenese im Verdauungstrakt von zooplanktonischen Organismen, und 4) Photomethanifizierung (die licht-induzierte Transformation von gelöstem organischen Kohlenstoff zu CH4). Auch werden Zusammenhänge zwischen Methanbildung und dem Abbau methylierter organischer Verbindungen wie Methylphosphonat und Dimethylsulphoniopropionat untersucht. Letztere kennt man als Stoffwechselprodukte während des Algenwachstums aus marinen Systemen, aber die Relevanz dieser Verbindungen in Seen (im Kontext der aeroben Methanogenese) ist noch unbekannt. Im Rahmen des Projektes werden auch saisonale Schwankungen der CH4 Ansammlung als möglich Folge jahreszeitlich schwankender Nährstoffkonzentrationen, variierender Primärproduktivität, und fluktuierender Algenvergesellschaftungen untersucht. Das ambitionierte Projekt repräsentiert einen ersten Versuch, die aerobe Methanbildung in Schweizer Seen zu verstehen und verspricht wichtige Erkenntnisse bezüglich der Kontrollmechanismen lakustriner CH4 Emissionen im allgemeinen. 

Direct link to Lay Summary Last update: 28.11.2016

Responsible applicant and co-applicants

Employees

Publications

Publication
Effects of climate change and episodic heat events on cyanobacteria in a eutrophic polymictic lake
Bartosiewicz Maciej, Przytulska Anna, Deshpande Bethany N., Antoniades Dermot, Cortes Alicia, MacIntyre Sally, Lehmann Moritz F., Laurion Isabelle (2019), Effects of climate change and episodic heat events on cyanobacteria in a eutrophic polymictic lake, in Science of The Total Environment, 693, 133414-133414.
Hot tops, cold bottoms: Synergistic climate warming and shielding effects increase carbon burial in lakes
Bartosiewicz Maciej, Przytulska Anna, Lapierre Jean‐François, Laurion Isabelle, Lehmann Moritz F., Maranger Roxane (2019), Hot tops, cold bottoms: Synergistic climate warming and shielding effects increase carbon burial in lakes, in Limnology and Oceanography Letters, 4(5), 132-144.

Collaboration

Group / person Country
Types of collaboration
Institut F.-A. Forel/University of Geneva Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
SUPSI Lugano (Dr. F. Lepori; Dr. A. Bruder) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Fachhochschule Nordwestschweiz (Prof. Dr. P. Corvini/Dr. M. Lenz) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Lake emissions rise Nature Climate Change International 2019
Media relations: print media, online media Warm on top, cold below: Uexpected greenhouse gas effect in lakes PhysOrg International 2019

Associated projects

Number Title Start Funding scheme
183294 QCL4CLUMPS: Simultaneous QC laser spectroscopic analysis of clumped 13C-D and D-D (2 x 2) isotopes in CH4 01.03.2020 R'EQUIP
160051 Copper availability, methanobactin production and methane oxidation in two Swiss lakes: Constraints on copper acquisition by methanotrophic bacteria 01.06.2016 Project funding (Div. I-III)
121861 Biogeochemical fluxes in South-Alpine Lakes: Linking nitrogen and methane dynamics in lacustrine redox-transition zones using a combined stable isotope and molecular approach 01.12.2008 Project funding (Div. I-III)
192327 The “methane paradox”: Mechanisms of CH4 production in oxygenated lake waters 01.07.2020 Project funding (Div. I-III)

Abstract

Methane (CH4) is a potent greenhouse gas with a 25 times higher global warming potential than CO2. Vast amounts of this gas are produced in natural wetlands and lakes. The multiple factors that control the balance between CH4 production and consumption, and in turn regulate the emission to the atmosphere, are still not fully understood. With this proposal, we seek funding for a continuation of SNF projects 121861 and 137636, the main objectives of which were to understand the modes of, and controls on, CH4 oxidation in the hypolimnion of eutrophic Lake Lugano. The previous efforts provided evidence for high rates of CH4 oxidation below the oxic-anoxic interface, which was primarily attributed to micro-aerobic CH4oxidation within the redox-transition zone in the mid-hypolimnion. Due to this efficient biological filter, only traces of CH4 from the sediments escape into the upper water column of the lake. However, our previous work also revealed subsurface accumulations of CH4 at the thermocline, leading to its net emissions from the lake surface into the atmosphere (up to 4600 mol day-1). The "methane paradox", i.e., the persistent CH4 supersaturation in oxic waters, was previously reported also for other lakes and the ocean, implying some unknown source of CH4 directly in the upper water column of these environments. The C-isotopic signature of subsurface CH4 in Lake Lugano points to biologic origin, yet the mechanisms leading to its formation remain unclear. The proposed research will aim at testing concurrent hypotheses with regards to the potential source of epilimnetic CH4, and at understanding the controls on the spatio-temporal dynamics of CH4 accumulation in Lake Lugano. Combining field and laboratory measurements, along with the employment of stable isotopic, radio-label, and molecular analyses, we will test for: i) CH4 production in association with phytoplankton productivity and anoxic microsites in sinking organic matter, ii) anaerobic CH4 production within the digestive tracts of zooplankton, and iii) the light-induced decomposition of dissolved organic carbon (photomethanification). We will specifically investigate CH4 production related to the exploitation (as nutrient source) and decomposition of methylated organic compounds. Some of these compounds (e.g., methylphosphonate and dimethylsulphoniopropionate) have been identified as components of phytoplankton biomass and/or metabolites during phytoplankton growth in the ocean, but their relevance in lacustrine ecosystems is unknown. Possible association between methanogens and zooplankton and/or phytoplankton aggregates will be elucidated by functional gene and lipid biomarker analysis. We will verify anticipated links between epilimnetic CH4 accumulation, the production of methylated compounds and other substrates used during methanogenesis, as well as trophic state (i.e., nutrient availability), phytoplankton productivity and community structure. Alternative explanations for the epilimnetic CH4 accumulations (e.g., transport of CH4 from the littoral zone and dissolution of CH4 bubbles) will also be examined. We hypothesize that the epilimnetic CH4 is primarily produced in situ, and that the release of CH4 into subsurface waters of Lake Lugano is modulated by the seasonal cycle of biological production and respiration. The proposed research will result in the first comprehensive characterization of epilimnetic CH4 production in a deep alpine lake. It will provide a milestone in our efforts to understand the “methane paradox” in lakes, helping us to gain insight into the biogeochemical controls on global CH4 emissions from terrestrial and aquatic environments. Finally, established links between CH4 production and biological productivity in the modern lake can provide the basis for temporal extrapolation. The proposed work may thus grant tools to augment our ability to predict future changes in the lacustrine CH4 emissions.
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