Modeling microplastic transport in open channel flows and ingestion dynamics by benthos

Area of Science:

• Environmental Science
• Aquatic Ecology
• Ecotoxicology

Background:

• Microplastic (MP) pollution is a pervasive environmental issue.
• Understanding microplastic ingestion by benthic organisms is vital for ecological risk assessment.
• Current knowledge on microplastic dynamics in benthos remains limited.

Purpose of the Study:

• To investigate the key factors influencing microplastic ingestion by benthic organisms.
• To develop and validate a numerical model for simulating microplastic-benthos interactions.
• To quantify the impact of benthos density, type, and microplastic density on ingestion dynamics.

Main Methods:

• Developed a high-fidelity, two-way coupled numerical model.
• Integrated large-eddy simulation and Lagrangian point-particle tracking.
• Examined benthos predation types (filter-feeders, grazers, burrowers), MP density, and benthos density.

Main Results:

• Benthos density is the dominant factor, with an eightfold increase leading to a 5- to 22-fold rise in ingested MPs.
• Grazers and filter-feeders showed higher ingestion efficiencies than burrowers.
• Two distinct ingestion transport models (suspension and sliding) were identified, differentiated by the Rouse number (P).

Conclusions:

• Benthos density and type significantly control microplastic ingestion dynamics.
• The Rouse number and turbulence intensity predict individual ingestion, while cumulative predation width reflects population-level impacts.
• A robust linear relationship was found between key parameters and the final microplastic ingestion proportion.