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Baur PA, Maier A, Buchsteiner C, Zechmeister T, Glatzel S. Consequences of intense drought on CO 2 and CH 4 fluxes of the reed ecosystem at Lake Neusiedl. ENVIRONMENTAL RESEARCH 2024; 262:119907. [PMID: 39251177 DOI: 10.1016/j.envres.2024.119907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 08/19/2024] [Accepted: 08/31/2024] [Indexed: 09/11/2024]
Abstract
Reed (Phragmites australis) dominated wetlands are commonly known as strong carbon (C) sinks due to the high productivity of the reed plant and C fixation in the wetland soil. However, little is known about the effects of drought on reed-dominated wetlands and the possibility of Pannonian reed ecosystems being a source of greenhouse gases (GHG). The drought at Lake Neusiedl had a particular impact on the water level, but also had consequences for the reed belt. Therefore, we investigated the drought-influenced C fluxes and their drivers in the reed ecosystem of this subsaline lake over a period of 4.5 years (mid-2018 to 2022). We applied eddy covariance technique to continuously quantify the vertical turbulent GHG exchange between reed belt & atmosphere and used vegetation indices to account for reed growth. Methane emissions decreased by 76% from 9.2 g CH4-C m-2a-1 (2019) to 2.2 g CH4-C m-2 a-1 (2022), which can be explained by the falling water level, the associated drying out of the reed belt and its consequences. Carbon dioxide emissions initially decreased by 85% from 181 g CO2-C m-2 a-1 (2019) to 27 g CO2-C m-2 a-1 (2021), but then increased to twice the 2019 level in 2022 (391 g CO2-C m-2 a-1). Due to the drying reed belt, the reed initially grew into formerly water-covered areas within the reed belt, especially in 2021, leading to higher photosynthesis through 2021. This development stopped and even reversed in 2022 as a consequence of the sharp decrease in sediment water content from about 65 to 32 Vol-% in mid-2022. Overall, drought led to a decoupling of the reed ecosystem from the open lake area and developed the wetland into a strong C source.
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Affiliation(s)
- Pamela Alessandra Baur
- University of Vienna, Faculty of Earth Sciences, Geography and Astronomy, Department of Geography and Regional Research, Working group Geoecology, Josef-Holaubek-Platz 2, Vienna, 1090, Austria; University of Vienna, Faculty of Life Sciences, Vienna Doctoral School of Ecology and Evolution (VDSEE), Djerassiplatz 1, Vienna, 1030, Austria.
| | - Andreas Maier
- University of Vienna, Faculty of Earth Sciences, Geography and Astronomy, Department of Geography and Regional Research, Working group Geoecology, Josef-Holaubek-Platz 2, Vienna, 1090, Austria
| | - Claudia Buchsteiner
- University of Vienna, Faculty of Earth Sciences, Geography and Astronomy, Department of Geography and Regional Research, Working group Geoecology, Josef-Holaubek-Platz 2, Vienna, 1090, Austria
| | | | - Stephan Glatzel
- University of Vienna, Faculty of Earth Sciences, Geography and Astronomy, Department of Geography and Regional Research, Working group Geoecology, Josef-Holaubek-Platz 2, Vienna, 1090, Austria; University of Vienna, Faculty of Life Sciences, Vienna Doctoral School of Ecology and Evolution (VDSEE), Djerassiplatz 1, Vienna, 1030, Austria
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Baur PA, Henry Pinilla D, Glatzel S. Is ebullition or diffusion more important as methane emission pathway in a shallow subsaline lake? THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 912:169112. [PMID: 38072262 DOI: 10.1016/j.scitotenv.2023.169112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 11/11/2023] [Accepted: 12/02/2023] [Indexed: 12/17/2023]
Abstract
Methane (CH4) emissions via ebullition contribute significantly to greenhouse gas emissions from freshwater bodies. According to the literature, the ebullition pathway may even be the most important pathway in some cases, particularly in shallow lakes. Ebullition rates are not often estimated because of the high uncertainty associated with episodic releases, leading to difficulties in their determination. This study provides an estimate of such emissions in a large, shallow, subsaline lake in eastern Austria, Lake Neusiedl, and compares them to the diffusion pathway. Ebullition gas sampling was conducted every 5-10 days over a period of 107 days from late March to mid-July 2021, using ebullition traps placed in three distinct locations: Reed belt, Channel and Open water/Lake. The aim was to study the temporal and spatial heterogeneity of ebullition and its contribution to total emissions. At the same time, several water quality and other environmental parameters were measured and then tested against the CH4 ebullition rates to explore them as potential drivers for this pathway. The carbon isotope fractionation factor (αC) of the measured CH4 ebullition gas, ranging from 1.03 to 1.06, indicates a dominance of the acetoclastic methanogenesis in the sediments of Lake Neusiedl, regardless of the location. The Reed belt location showed the highest mean CH4 ebullition rate (17 ± 28 mg CH4 m-2 d-1), which is >340-fold higher than the mean of the other two locations, and demonstrated also a strong temperature dependency. In all locations at Lake Neusiedl, the median CH4 fluxes via diffusion are significantly higher than via ebullition. Our analyses do not confirm the dominance of the ebullition pathway in any of the studied locations. Whereas at the Reed belt, ebullition accounts for 48 % of the CH4 emissions, in the other two locations, is responsible only for about 1 %.
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Affiliation(s)
- Pamela Alessandra Baur
- University of Vienna, Faculty of Earth Sciences, Geography and Astronomy, Department of Geography and Regional Research, Working group Geoecology, Josef-Holaubek-Platz 2, Vienna 1090, Austria; University of Vienna, Faculty of Life Sciences, Vienna Doctoral School of Ecology and Evolution (VDSEE), Djerassiplatz 1, Vienna 1030, Austria.
| | - Daniela Henry Pinilla
- University of Vienna, Faculty of Earth Sciences, Geography and Astronomy, Department of Geography and Regional Research, Working group Geoecology, Josef-Holaubek-Platz 2, Vienna 1090, Austria.
| | - Stephan Glatzel
- University of Vienna, Faculty of Earth Sciences, Geography and Astronomy, Department of Geography and Regional Research, Working group Geoecology, Josef-Holaubek-Platz 2, Vienna 1090, Austria; University of Vienna, Faculty of Life Sciences, Vienna Doctoral School of Ecology and Evolution (VDSEE), Djerassiplatz 1, Vienna 1030, Austria.
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