Quantifying the inhibitory impact of soluble phenolics on anaerobic carbon mineralization in a thawing permafrost peatland

Abstract

The mechanisms controlling the extraordinarily slow carbon (C) mineralization rates characteristic of Sphagnum-rich peatlands (“bogs”) are not fully understood, despite decades of research on this topic. Soluble phenolic compounds have been invoked as potentially significant contributors to bog peat recalcitrance due to their affinity to slow microbial metabolism and cell growth. Despite this potentially significant role, the effects of soluble phenolic compounds on bog peat C mineralization remain unclear. We analyzed this effect by manipulating the concentration of free soluble phenolics in anaerobic bog and fen peat incubations using water-soluble polyvinylpyrrolidone (“PVP”), a compound that binds with and inactivates phenolics, preventing phenolic-enzyme interactions. CO2 and CH4 production rates (end-products of anaerobic C mineralization) generally correlated positively with PVP concentration following Michaelis-Menten (M.M.) saturation functions. Using M.M. parameters, we estimated that the extent to which phenolics inhibit anaerobic CO2 production was significantly higher in the bog—62 ± 16%—than the fen—14 ± 4%. This difference was found to be more substantial with regards to methane production—wherein phenolic inhibition for the bog was estimated at 54 ± 19%, while the fen demonstrated no apparent inhibition. Consistent with this habitat difference, we observed significantly higher soluble phenolic content in bog vs. fen pore-water. Together, these findings suggest that soluble phenolics could contribute to bogs’ extraordinary recalcitrance and high (relative to other peatland habitats) CO2:CH4 production ratios.

Microbial polyphenol metabolism is part of the thawing permafrost carbon cycle

“…Polyphenols have long been cited as controllers of peatland carbon cycles through the enzyme latch mechanism. The studies proposing and supporting this role have historically measured the impact of polyphenols on net outputs of carbon mineralization [7][8][9]26 . We collected similar data, but also focused on the interplay between polyphenols and the microbiome in situ using multi-omics (Fig.…”

“…Here we sought to revisit the fundamental assumptions of the enzyme latch theory and to more broadly describe microbial polyphenol transformations expressed in peatland soils. We selected a model Arctic permafrost peatland, Stordalen Mire 5,24 , where the enzyme latch theory has been suggested to mediate carbon storage [25][26][27] . At this site, natural thaw created three distinct habitats from dry, intact permafrost palsa through a partially thawed bog with a fluctuating water table, to a fully thawed and saturated fen (Supplementary Fig.…”

Phosphorus Supply to Plants of Vaccinium L. Genus: Proven Patterns and Unexplored Issues

“…The remaining available Pi is converted into Po by living organisms, but the reverse process is slowed down due to the inhibition of the activity of decomposer microorganisms in an acidic environment, anaerobic conditions in the thickness of peat sediments, and the accumulation of compounds with antimicrobial properties or inhibitors of extracellular enzyme activity [22]. In this regard, in acidic soils, up to 90% of phosphorus accumulates in the form of various organic compounds, mainly represented by phosphomonoesters and phosphodiesters [23,24].…”

Does Shift in Vegetation Abundance After Nitrogen and Phosphorus Additions Play a Key Role in Regulating Fungal Community Structure in a Northern Peatland?

“…For example, a shift in the composition of plant functional type (PFT) could alter the input of litter shedding from distinct PFTs with very different litter quality ( Dorrepaal et al, 2005 ; Moore et al, 2008 ; Ward et al, 2015 ). The leached soluble phenolic compounds from litters could retard the metabolic activities of soil microorganisms, which are imperative in modulating peatland C stocks ( Zak et al, 2019 ; Fenner and Freeman, 2020 ; Cory et al, 2022 ).…”