Understanding the Fate and Transport of Microplastics at Buoyant River Outflows

A drawing of where a river outflow meets the ocean. On the left side of the image, the river outflow, also known as a river plum, is lighter in color compared to the right side of the ocean image which is a darker blue.

Rutgers University will study the movement of microplastics down the Delaware River to the confluence with Delaware Bay, and determine the role this mixing area may play as the entry point for microplastics into the food chain. 

Type of Project: Research 

Region: Mid-Atlantic

Project Dates: August 2019 - July 2021

Who is involved?
With the support of a NOAA Marine Debris Program Research Grant, Rutgers University (Department of Marine and Coastal Sciences, Civil and Environmental Engineering, and Department of Chemistry), will combine field data and laboratory experiments to understand the vertical and horizontal movement of microplastics as they leave the Delaware Bay and enter the coastal environment, an area known as a frontal system. They will also assess the role these frontal systems play in the incorporation of microplastics in the marine food web. 

What is the project and why is it important?
Rivers are thought to be a major pathway for marine debris (including microplastics) to enter coastal areas. However, the movement of microplastics from land to the coastal areas and deep ocean is poorly understood. The movement of microplastics as rivers merge with coastal waters in frontal systems is also poorly understood, due to changes in salinity, biological activities, etc. Because rivers transport large amounts of nutrients to the coast, these frontal systems contain a high concentration of planktonic organisms. Generally, many factors (river flow conditions, salinity, biological activity, wind, currents, etc.) may influence the movement and distribution of microplastics as they enter coastal waters. 

This project will combine field observations and laboratory experiments to assess the role that circulation and biological processes at river plume fronts play in the movement of microplastics in the Delaware River/Bay. The project will conduct sampling across the mouth of Delaware Bay to compare plastic particle distribution, polymer (plastic) type, shape, and abundance across a range of salinity gradients during both high and low river flow conditions. A microplastic feeding experiment using select species of zooplankton (microscopic organisms), will be completed to determine the role of these frontal systems as an entry point for microplastics into the food chain. They will also analyze the waste produced by the zooplankton, known as fecal pellets, to determine how much microplastic is eliminated from the organism and how the density of the plastic affects the sinking rate of the fecal pellets to the sea floor. The results from the field and lab studies will be incorporated into a Regional Ocean Modeling System (ROMS) framework for the Delaware Bay. This model will allow researchers to understand the movement of microplastics as they enter coastal areas due to a number of variables, including changes in salinity, uptake of microplastics into zooplankton and the resulting sinking of fecal pellets and microplastics, river flow conditions, and compare these to other environmental variables that affect microplastic movement like wind and surface currents. This project will provide critical insights to the uptake of microplastics into the food chain by marine animals and in turn how that impacts the movement of microplastics entering coastal areas.