Coastal Export and Fate of Microplastics in the Southern California Bight

Clear, round dish hold many tiny crabs and microplastics in water.

The University of California at Riverside and partners will investigate the source and pathways of microplastics, using modeling and field measurements of riverine and wastewater treatment inputs, to better understand the fate and transport of microplastics in the Southern California Bight (SCB).

Type of Project: Research 

Region: California

Project Dates: August 2019 - July 2021

Who is involved?
With the support of a NOAA Marine Debris Program Research Grant, researchers from the University of California Riverside, University of California Los Angeles (Department of Atmospheric & Oceanic Sciences), and the Southern California Coastal Water Research Project (SCCWRP), will investigate the fate and transport of microplastics in the SCB. The Orange County Sanitation District (OCSD) and Algalita Foundation will assist with the collection of samples in coastal and nearshore waters. 

What is the project and why is it important?
Much remains unknown about the sources, abundance, and distribution of microplastics which can impede regional conversations on potential management strategies. Improved monitoring and modeling tools to track microplastic sources, pathways, and fate can guide more cost-effective management strategies in the SCB. 

Through field measurements and modeling exercises, this project will determine major microplastic pathways and investigate mechanisms controlling the fate of microplastics to nearshore waters of the SCB. Researchers will describe the variability in microplastic concentrations in river and wastewater treatment plant ocean outfalls into San Pedro Shelf, due to wet and dry seasons. Collection of field data under these variable conditions will allow scientists to develop concentration-water discharge rating curves. Essentially, scientists will be able to predict microplastic concentrations in the river given changes in the amount and speed of water moving through the river.

Next, a microplastic fate and transport module will be developed for use within the Regional Ocean Model System (ROMS) for the SCB. ROMS is used to model how a section of the ocean responds to physical forcings, such as heat or wind. Microplastics data from riverine and wastewater treatment plant inputs will be used to populate the ROMS model. This modeling approach will allow researchers to make predictions about the movement of microplastics where extensive sampling is not possible. The framework and toolset to assess the coastal export and fate of microplastics (as developed in this project), will enable coastal managers to frame management decisions within realistic and informed projections of microplastic distribution.