By KATE HABREL
Capital News Service
Sampling Lake Michigan surface water near Milwaukee, Wisconsin. Image: Peter Lenake
LANSING — The Huron River near Ann Arbor had the greatest concentration of microplastic pollution, a recent study of Great Lakes tributaries shows.
It also had the most plastic fragments in a study that categorized microplastics beyond the beads in consumer products like body wash identified in earlier studies.
The study by Austin Baldwin, a hydrologist at the Wisconsin Water Science Center of the U.S. Geological Survey (USGS), categorized the plastic as beads, fragments, foams or fibers. Fragments are broken pieces of larger plastics, foams are filmy materials like bags and fibers include fishing line, rope and other fine materials.
A map of Baldwin’s sampling sites. Image: Austin Baldwin
Baldwin’s team sampled 29 Great Lakes tributaries during the spring of 2014 and 2015.
“Of those categories, by far, we saw the most fibers,” Baldwin said. “About 72 percent of the particles we sampled were these fibers.”
The highest concentration of all microplastics, more than 32 particles per cubic meter, was measured in the Huron River.
And none were found at the Manitowoc River at Manitowoc, Wisconsin, or Burns Ditch at Portage, Indiana, two rural sampling sites.
Baldwin expected to find higher concentrations of microplastics near urban watersheds. For the most part, he did. However, fibers were found in high concentrations in both urban and agricultural watersheds.
The highest concentration of fibers was measured in the Ashtabula River at Ashtabula, Ohio. The highest concentration of beads and the highest concentration of foams were measured in the Buffalo River at Michigan Avenue in Buffalo, New York.
Further testing will determine what effect the fibers have on the Great Lakes environment.
Researcher Ben Siebers on towing vessel. Image: Austin Baldwin
“They’re definitely ingested by fish and other organisms,” Baldwin said. “Whether that has a real impact on fish health is still being debated in the studies.”
Baldwin’s study was published in Environmental Science & Technology. His work has sparked new interest in microplastics – particularly fibers.
Two related studies are underway to help scientists further understand microplastics’ distribution through the Great Lakes. One focuses on Lake Michigan and Lake Erie.
“We’re looking for microplastics in the sediment,” said Steven Corsi, a research hydrologist with the USGS who assisted with Baldwin’s research. The studies were funded by the Great Lakes Restoration Initiative, a federal program dedicated to the restoration and protection of the Great Lakes.
Peter Lenaker measures current velocity on the Menomonee River. Image: Molly Breitmun
Previous studies have focused on plastic that floats on the surface of the water. Corsi said he hopes to find out which types of microplastics collect where. Fiber concentration is expected to be higher at the bottom of the lakes.
Another USGS study is looking at the Milwaukee Harbor area. Researchers are sampling sediment and water from the confluence of the Kinnickinnic, Menominee and Milwaukee rivers. They are also sampling from the inner and outer Milwaukee Harbor area.
This study uses the same gathering nets Baldwin’s study used. These nets are placed along a cable that measure microplastics at specific depths. The cable trails behind a research vessel to collect samples.
Paul Reneau, left, and Peter Lenaker taking water samples on Lake Michigan. Image: David Housner
Peter Lenaker, a physical scientist for the USGS in Wisconsin, is doing that research with the Milwaukee Metropolitan Sewer District. He said he hopes to better understand what is happening to microplastics below the water.
“If you scour the literature, that really hasn’t been done before,” Lenaker said. “Everyone that’s sampled has either sampled sediment or the top of the water column, which can range depending on how people sample. This project will hopefully provide some unique results as to what’s happening through the whole water column.”
Researchers at a sampling site for the Baldwin study. Image: Austin Baldwin
Both studies seek to provide more information about microplastics.
“We’re just trying to collect the best data we can and provide that to the public and policy makers, and they can inform themselves based on that research,” Lenaker said. “There’s a lot that we don’t know about microplastics. So the more we can figure out, the better.”
Kate Habrel writes for Great Lakes Echo.