oxidases; ombrotrophic bogs; high resolution mass spectrometry; carbon cycling; enzymic latch; northern peatlands; electrochemistry; phenols; enzymatic oxidation; electron transfer
Gao Chuanyu, Sander Michael, Agethen Svenja, Knorr Klaus-Holger (2019), Electron accepting capacity of dissolved and particulate organic matter control CO2 and CH4 formation in peat soils, in Geochimica et Cosmochimica Acta
, 245, 266-277.
Önnby Linda, Walpen Nicolas, Salhi Elisabeth, Sander Michael, von Gunten Urs (2018), Two analytical approaches quantifying the electron donating capacities of dissolved organic matter to monitor its oxidation during chlorination and ozonation, in Water Research
, 144, 677-689.
Walpen Nicolas, Lau Maximilian P., Fiskal Annika, Getzinger Gordon J., Meyer Stefan A., Nelson Taylor F., Lever Mark A., Schroth Martin H., Sander Michael (2018), Oxidation of Reduced Peat Particulate Organic Matter by Dissolved Oxygen: Quantification of Apparent Rate Constants in the Field, in Environmental Science & Technology
, 52(19), 11151-11160.
Walpen Nicolas, Getzinger Gordon J., Schroth Martin H., Sander Michael (2018), Electron-Donating Phenolic and Electron-Accepting Quinone Moieties in Peat Dissolved Organic Matter: Quantities and Redox Transformations in the Context of Peat Biogeochemistry, in Environmental Science & Technology
, 52(9), 5236-5245.
Walpen Nicolas, Schroth Martin H., Sander Michael (2016), Quantification of Phenolic Antioxidant Moieties in Dissolved Organic Matter by Flow-Injection Analysis with Electrochemical Detection, in Environmental Science & Technology
, 50(12), 6423-6432.
Northern peatlands, including ombrotrophic bogs, store significant amounts of carbon in the form of peat organic matter. Sphagnum mosses, which are well adapted to the nutrient poor, acidic and wet conditions common to bogs, dominate these ecosystems and actively secrete allelopathic phenolic compounds into bog porewaters. The dissolved phenols possess antimicrobial and enzyme inhibiting properties, which contribute to slow rates of microbial organic matter decomposition. Long hydraulic retention times and low lateral flow in bogs limit physical dissolution, restricting phenol removal to chemical oxidation by extracellular phenol oxidases and peroxidases. These oxidases require molecular oxygen as a co-substrate and are therefore only active in the uppermost, oxygenated part of the bog, the so-called acrotelm. Phenol dynamics in bogs have received considerable research interest in light of the ‘enzymic latch’ hypothesis, which predicts that oxygenation of peats, e.g., due to climate change, would activate oxidase enzymes and thus lower phenol concentrations, starting a cascade of processes that ultimately releases significant fractions of the stored carbon. The work proposed herein aims to overcome existing knowledge gaps in the dynamics of low molecular weight phenols in surface bog porewaters by quantifying dissolved Sphagnum-derived phenols and by providing the first systematic investigation of enzymatic reaction pathways salient to those phenols. To that end, we first propose development of a suite of novel analytical techniques, based on state-of-the-art mass spectrometric and electrochemical techniques, allowing the sensitive and selective determination of specific dissolved low molecular weight phenolic compounds in dilute bog porewater samples and the structural and functional (i.e., redox state) characterization of enzymatic phenol oxidation products. We then propose application of these validated methodologies to determine phenol dynamics in simulated and field collected bog water samples with discrete phenolic substances and selected oxidases. Finally, we propose a confluence of laboratory-based mechanistic studies and natural bog conditions by field studies measuring oxygen gradients, phenol contents, and oxidase activities along vertical redox and activity gradients from the partially oxic acrotelm to the permanently water-saturated and anoxic catotelm in ombrotrophic bogs in Sweden. Overall, the proposed work will advance current knowledge of the biogeochemical roles of dissolved phenols in northern peatlands and their role in peatland carbon dynamics. The proposed work will be carried out by one PhD student and one postdoctoral research fellow.