Journal Article
Biogeosciences, vol. 20, iss. 16, pp. 3449-3457, 2023
Authors
Emily B. Graham, Hyun-Seob Song, Samantha Grieger, Vanessa A. Garayburu-Caruso, James C. Stegen, Kevin D. Bladon, Allison N. Myers-Pigg
Abstract
Abstract. Pyrogenic organic matter (PyOM) from wildfires impacts river
corridors globally and is widely regarded as resistant to biological
degradation. Though recent work suggests PyOM may be more bioavailable than
historically perceived, estimating bioavailability across its chemical
spectrum remains elusive. To address this knowledge gap, we assessed
potential bioavailability of representative PyOM compounds relative to
ubiquitous dissolved organic matter (DOM) with a substrate-explicit model.
The range of potential bioavailability of PyOM was greater than natural DOM;
however, the predicted thermodynamics, metabolic rates, and carbon use
efficiencies (CUEs) overlapped significantly between all OM pools. Compound type
(e.g., natural versus PyOM) had approximately 6-fold less impact on predicted
respiration rates than simulated carbon and oxygen limitations. Within PyOM,
the metabolism of specific chemistries differed strongly between unlimited
and oxygen-limited conditions – degradations of anhydrosugars, phenols, and polycyclic aromatic hydrocarbons (PAHs) were more favorable under oxygen
limitation than other molecules. Notably, amino sugar-like, protein-like, and lignin-like PyOM had lower carbon use efficiencies relative to natural DOM
of the same classes, indicating potential impacts in process-based model
representations. Overall, our work illustrates how similar PyOM
bioavailability may be to that of natural DOM in the river corridor,
furthering our understanding of how PyOM may influence riverine
biogeochemical cycling.
