56 / 2025-03-29 20:28:41

Hydrodynamic Controls on Microbial Activities and Organic Carbon Cycling in Resuspended Sediments of Marginal Seas

Hydrodynamics, Sediments resuspension, Microbial ecology, Organic carbon cycling, Sediments transport, Marginal seas

Theme 2: Geobiology of Modern Habitable Earth > Session 2a: Microbe-mediated Carbon Cycling on Modern Earth

    Marginal seas serve as critical zones for organic carbon (OC) preservation, where sediments resuspension-driven by hydrodynamic forces-plays a crucial role in regulating carbon cycling. However, the mechanisms governing intermediate processes remain poorly constrained. Our studies integrate findings from microbial ecology, molecular dynamics simulations, and sediment geochemistry to unravel how resuspension influences OC degradation and preservation in shallow marine environments.

    First, we use molecular dynamics simulations to reveal that oxygen exposure during resuspension and lateral transport significantly degrades lignin, a traditionally refractory OC component, reducing its preservation efficiency and challenging its role as a refractory OC sink. Furthermore, we find refractory OC utilization may be mediated by microorganisms through simulated micro-erosion experiments and biomarker determination. Simulated micro-erosion experiments demonstrate that hydrodynamic disturbances selectively reshape microbial communities in resuspended sediments, favoring capable of degrading different compositions of OC and enhancing remineralization rates. Phospholipid fatty acids (PLFAs) and their compound-specific isotopes show the changes in microbial community composition and metabolism, revealing microorganisms can metabolize and utilize refractory OC and produce metabolic by-products belonging to pre-aged OC, which explains the reason why refractory OC can be oxidized. Finally, we integrate field and modeling evidence to clarify the intermediate processes of microbial oxidation of refractory OC, and propose that resuspension acts as a key mechanism for OC redistribution, reactivating buried OC into the water column and modulating its fate between mineralization, reburial, and export.

    Overall, these findings highlight that sediments resuspension act as a critical driver of carbon dynamics in marginal seas. By integrating microbial ecology, geochemistry, and computational modeling, we provide a systematic framework for understanding how hydrodynamic forces regulate OC persistence and turnover. These insights have important implications for predicting carbon sequestration efficiency in dynamic coastal systems under changing climate conditions.