An Integrated Experimental and Modeling Approach to Predict Sediment Mixing from Benthic Burrowing Behavior

Area of Science:

• Aquatic Ecology
• Biogeochemistry
• Sediment Dynamics

Background:

• Bioturbation is a key process in aquatic environments, influencing sediment biogeochemistry and contaminant fate.
• Current bioturbation models often oversimplify organism behavior, limiting their predictive power.

Purpose of the Study:

• To develop and validate a novel experimental and modeling approach for quantifying sediment mixing due to bioturbation.
• To directly link burrow formation by benthic organisms to sediment redistribution patterns.

Main Methods:

• Paired white-light and fluorescence imaging to track burrow formation and tracer particle movement.
• Utilized time-lapse imagery of oligochaete (Lumbriculus variegatus) burrowing.
• Developed a parsimonious random walk model parameterized by observed burrowing statistics and organism density.

Main Results:

• Observed heterogeneous bioturbation with varied burrowing depths and durations.
• Documented sediment homogenization near the surface and rapid particle transport to deeper layers.
• The developed random walk model successfully captured key features of heterogeneous sediment mixing, including surface and deep transport dynamics.

Conclusions:

• The novel approach provides a more realistic representation of bioturbation than simplified biodiffusion models.
• The parsimonious random walk model offers a general and transferable framework for linking sediment transport to biophysical processes.
• This research enhances understanding of how organism behavior shapes sediment biogeochemistry and contaminant fate.