A unified theory for organic matter accumulation

Abstract

Organic matter constitutes a key reservoir in global elemental cycles and the biological sequestration of carbon. However, our understanding of the dynamics of organic matter and its accumulation remains incomplete. Seemingly disparate hypotheses have been proposed to explain organic matter accumulation: the slow degradation of intrinsically recalcitrant substrates, the depletion to concentrations that inhibit microbial consumption, and a dependency on the consumption capabilities of nearby microbial populations. Here, using a mechanistic model, we develop a theoretical framework that explains how organic matter predictably accumulates due to biochemical, ecological, and environmental factors. The new framework subsumes the previous hypotheses. Changes in the microbial community or the environment can move a class of organic matter from a state of functional recalcitrance to a state of depletion by microbial consumers. The model explains the vertical profile of dissolved organic carbon in the ocean, and it connects microbial activity at subannual timescales to organic matter turnover at millenial timescales. The threshold behavior of the model implies that organic matter accumulation may respond nonlinearly to changes in temperature and other factors, providing hypotheses for the observed correlations between organic carbon reservoirs and temperature in past earth climates.

Ecological stochasticity and phage induction diversify bacterioplankton communities at the microscale

“…These results contrast with those of previous studies on the replicability of microbial community assembly at the functional level (21,22) likely because of the homogenizing effect of macroscale sampling. Intriguingly, the lognormal-like distribution of biomass on individual particles aligns with observations and predictions of lognormally-distributed global marine organic matter export and remineralization rates; these distributions may repeatedly emerge as a reflection of the multiplicative effects of stochastic variables in ecological settings (50)(51)(52). Although our experimental system significantly simplified the process of POM degradation in the ocean, our approach provides a quantitative link between the microscale and larger-scale processes, highlighting the importance of considering local variability when investigating the mechanisms behind microbial community development in a spatially structured environment.…”

Estimating Mass Flux From Size‐Fractionated Filtered Particles: Insights Into Controls on Sinking Velocities and Mass Fluxes in Recent U.S. GEOTRACES Cruises

“…Given the similar temperatures and sinking velocities but contrasting transfer efficiencies between the GA03 and GP16 cruises, however, other factors may control remineralization rate. Such factors could relate to differences in the organic and inorganic composition of particles, or colonization of particles by microbial heterotrophs with the appropriate metabolic capability that may make the GA03 particles more functionally recalcitrant (cf., Zakem et al., 2021). For example, LSF particles in the GA03 gyre are characterized by higher fractions of lithogenic particles and lower fractions of CaCO 3 and biogenic opal when compared to the GP16 gyre.…”

Long-term Fertilization Enhances Soil Carbon Stability by Increase the Ratio of Passive Carbon: Evidence From Four Typical Croplands

“…In addition, fertilization might facilitate microbe growth and proliferation (Feyissa et al 2020), hence lead to the increased input of microbial necromass which is associated with the mineral-associated organic matter and thus cause accumulation of C in the recalcitrant fraction (Ma et al 2018). Moreover, AC is very sensitive to climate change or anthropogenic disturbance and is easily decomposed (Ding et al 2016b;Zakem et al 2021). Overall, because AC decomposes rapidly and quickly, it may get into a new equilibrium with inputs matching outputs, reducing the RR.…”