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[ID: 320] Restored wetlands - Hotspots for methane emission and mercury methylation?

PI: Jacob Smeds

Wetlands are unique ecosystems delivering important ecosystem services to society. Due to extensive drainage only a minor fraction of the original wetland areas still remains in e.g. Europe. During the last decades, wetland restoration has become a prioritized environmental protection action in many European countries. Also the Swedish government has defined wetland restoration as major national undertaking, with numerous authorities and landowners actively involved. The major objectives behind wetland restoration are increased biodiversity, increased carbon sequestration, increased groundwater storage and improved surface water quality. However, wetland restoration also causes fundamental changes in biogeochemical properties and may result in undesired impacts and potential environmental threats. In addition, a century or more of drained conditions has drastically changed the soil properties in relation to natural wetlands and this is likely to profoundly influence the potential for various biogeochemical processes. This renders the impact of restoration on biogeochemical processes difficult to predict. Methane is the second most important green-house gas after carbon dioxide. Another process of grave concern is mercury (Hg) methylation. The overall aim of the project is to identify properties of rewetted wetlands that are critical for methane dynamics (including both production and consumption) and for the transformation of inorganic Hg to elemental gaseous Hg and the toxic MeHg molecule. We will the compare these properties and the associated biogeochemical pathways relative adjacent undisturbed natural wetlands. Understanding these biological systems will be fundamental for developing strategies to minimize emissions of the greenhouse gas methane and concentrations of methyl mercury in ground and surface waters of our landscape following wetland restoration.

WetlandrestorationmethaneHg

[ID: 141] Exploring the Greenhouse Gas Balance of a Boreal Forest Landscape using Tall Tower Eddy Covariance Measurements

PI: Anne Klosterhalfen

With the tall tower eddy covariance measurements of CO2, CH4, and H2O fluxes (Svartberget), the GHG budgets can be derived directly for the Krycklan catchment on the landscape-scale. In addition, local source and sink contributions to this direct landscape-scale estimate will be investigated via advanced footprint modeling.

carbon dioxidemethanewater vaporfootprint modelinglandscape scale

[ID: 124] Anaerobic Oxidation of Methane in Terrestrial Ecosystems (AOMTE): mechanisms and ecological relevance

PI: Maxim Dorodnikov

Anaerobic oxidation of methane (AOM) is a microbial process of methane (CH4) consumption under anoxic conditions with various terminal electron acceptors (other than oxygen), e.g. sulfate, nitrate, nitrite, some metals (Fe, Mn) or organic compounds. AOM is common in marine ecosystems, where microbial sulfate reduction consumes most of the CH4 produced in sediments. Despite the global significance of AOM, the mechanisms (specific electron acceptors, microbial groups, etc.), optimal conditions and AOM relevance in terrestrial ecosystems are almost unknown. Therefore, there is a strong need for investigation of AOM in terrestrial ecosystems, especially those exposed to prolonged anaerobic conditions such as natural or restored peatlands and rice paddies. This proposal focuses on the AOM mechanisms and intensity within a large climate gradient in four research sites: one natural peatland in Sweden, one restored peatland in Germany and one rice paddy field in China. To estimate the in situ AOM rate, the belowground 13C-CH4 labeling is efficiently applied. The product of AOM - released 13CO2 - together with the dynamics of porewater electron acceptors allows assessing the AOM intensity and links it to existing environmental conditions at each of the sites. Along with the field studies, the specific mechanisms and the microbial groups driving AOM is thoroughly investigated in a set of laboratory experiments with the soils from all research sites. Application of novel methods of electrochemical analysis (measurement of electron exchange capacities of the electron acceptors), 13C tracing in 13CO2 produced by 13CH4 oxidation and in PLFA and GDGT biomarkers (proxies for bacterial and archaeal communities) will reveal the optimal conditions for the highest potential AOM rates and determine microbial groups responsible for AOM. To our knowledge, the current proposal is the first attempt to estimate the in situ AOM rate and to determine the responsible microbial groups in a range of ecosystems with sustained CH4 production on Eurasian continent. Finally, understanding of AOM mechanisms may change the existing concept of CH4 cycling in terrestrial ecosystems and will improve current process-based models of regional and global carbon balance.

methaneanaerobic methane oxidationbelowground labeling