Tracing cyclic redox reactions of Organic Matter in Lakes

• Applicant: Professor Maximilian Peter Lau, Ph.D.
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2017 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 386619524

This research project will explore a previously disregarded linkage between two components of freshwater biogeochemistry:(a) Stratified lakes can feature pelagic redox interfaces. Any matter that passes through this interface is subjected to drastic changes in oxygen availability.(b) Microorganisms may reduce quinone moieties in dissolved organic matter (DOM) when used as terminal electron acceptor (TEA) in anaerobic respiration. The reduced moieties may be rapidly re-oxidized upon dislocation to oxic environments.In earlier works, the microbial reduction and subsequent abiotic oxidation of DOM was shown to occur reversibly. Also, the oxidized DOM may release microbial communities from TEA limitation. This proposal builds on the hypothesis that the rapid cycling between oxidized and reduced states may be a widespread phenomenon at transient aquatic interfaces. In these spatiotemporal niches, a significant share of biomass degradation might be coupled to the reversible reduction of DOM. Here, we specifically aim for the first quantification of ecosystem respiration channeled through this pathway. The research will address temperate and boreal lakes since they represent a major fraction of global fresh waters and typically feature the physicochemical conditions necessary for tightly coupled DOM redox cycles. We expect considerable implications for greenhouse gas production due to the competitive inhibition of less favorable respiration pathways including methanogenesis. In light of the increasing transport of terrestrial organic carbon to boreal surface waters, this mechanism is critical to the prediction of global aquatic carbon dioxide and methane emissions.The project will span multiple scales and include laboratory and field experiments to model the relevance of respiration with DOM as TEA in lacustrine environments. Hence, the proposed research across Canadian lakes will increase the mechanistic understanding of DOM redox cycling including its role in aquatic carbon turnover.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professor Dr. Paul del Giorgio