Enlighten Me: UD scientists comb Delaware Bay for tiny bits of plastic
Tiny pieces of plastics, called “microplastics” are inundating our oceans.
Right now, we don’t know how deep they go below the surface, or how they affect ocean health, but University of Delaware researchers are combing the Delaware Bay to determine the scope of these microplastics in our waterways.
Jonathan Cohen stood on a boat near Bowers Beach scanning the water for microscopic pieces of plastic.
“I would expect that we would see little microbeads, the kinds of things that were in cosmetics but are being phased out, I would expect to see a lot of little fibers, things that kind of come off of ropes, or come off of clothing like fleeces…” Cohen said.
Cohen is a marine science professor with the University of Delaware. He and a crew are pumping water from the bay into a net.
They lower a pump about a half meter into the water.
Water starts to flow through the pump to a series of tubes. It settles in a net with holes about the width of a human hair. Then, they spray the net from the top down to wash pieces of plastic into a cup at the bottom.
They pour the sample into a glass jar and add preservatives in case their sample picked up any living organisms.
Cohen holds the jar up and takes a closer look.
“Sometimes you can pick it out with the naked eye - particularly the colorful stuff, but oftentimes you have to wait actually for this foam to kind of subside and it tends to be in this layer at the surface,” Cohen said.
He's looking for tiny, broken down pieces of plastic less than 5 millimeters in dimeter.
The researchers repeat this process at 1 meter, 2 meters and 3 meters down. Then, they tow a net on the surface for five minutes, grabbing about 200 cubic meters of water. That’s the typical way researchers look for microplastics.
Scientists have long collected microplastics from the surface, but Cohen said the deeper we go, the less we know.
“We don’t know if you go down a half meter or another half meter or another half meter what sorts of things you’ll find, what the concentration will be. Is there a large concentration at the surface then as you go down there’s less and less?” Cohen said.
It depends on how buoyant the pieces of plastics are, and how much they get moved around by currents and tides, Cohen said.
“When we sample upstream — so areas near the Cherry Island Landfill in the Wilmington area — we see relatively high levels of microplastics, and as we go down in the bay passing the station where we are now and even further down towards Lewes, we see sort of a decline in microplastics,” Cohen said.
Cohen said they don’t know why there seems to be more plastics in urban areas.
Microplastics are in some of the products we use every day, from face wash to fleece jackets. With a single wash of your face or jacket, they travel from the drain to the ocean.
Lab Technician Haley Glos said their research has made her more aware of what’s in the products she buys. She thinks about the samples collected just minutes ago on the boat.
“You can see the plastics whether it’s little fragments or like I said, microbeads, fibers, it’s really amazing and it just makes you more conscious because this stuff is breaking down and it makes you wonder where is it going next when it’s not in the water,” Glos said.
Cohen’s lab wonders if microplastics could be washing up in the sand.
The Department of Natural Resources and Environmental Control’s Delaware Coastal Programs is testing that. They’re trying to understand if there’s any connection between the water where Cohen is sampling and the beach.
“It will allow for some sort of connectivity between the land and sea,” said Kari St. Laurent, an environmental scientist with Delaware Coastal Programs. “We can’t necessarily say that the two are connected but it will help start to fill in the picture of what Delaware Bay looks like.”
Delaware Coastal Programs is trying out different ways of looking for microplastics in the sand at Bowers Beach, Kitts Hummock and the Ted Harvey Wildlife Area.
“If we find a spot where we have a lot of microplastics, it might tell us something about the source and fate of microplastics. It might help us understand better where they’re coming from, where they’re aggregating,” St. Laurant said.
That will help scientists produce hotspots — areas where microplastics are more likely to be accumulating.
Cohen said that connectivity is something he and his lab will continue to look into. He said he’d like to eventually study how microplastics could affect sea life that eat them.
For now, Cohen and his team are only beginning to wade into what there is to know about microplastics in the Delaware Bay.