LANSING - Plastic pollutants circulate in pockets of the Great Lakes at concentrations higher than any other body of water on Earth, according to a recent study.
The study is the first to look at plastic pollutants in the Great Lakes and is part of a larger global endeavor to understand the origin and prevalence of plastic pollution in water.
"We had two samples in Lake Erie that we just kept going back and rechecking the data, because the count, the number of plastic particles in the sample, was three times greater than any sample collected anywhere in the entire world," said chemistry professor and project leader Sherri Mason of the State University of New York (SUNY) at Fredonia.
Mason's team of 20 students embarked this summer aboard the US Brig Niagara, the rebuilt flagship that won the Battle of Lake Erie during the War of 1812.
Beginning in Lake Superior in July, the team sailed south through Lake Huron and into Lake Erie, collecting water samples as it traveled for three weeks.
Twenty-one samples were collected with a net trailing from the vessel.
They found the least plastic in Lake Superior, with concentrations increasing as they sailed south. That's because water flows south from Lake Superior through Lake Huron and into lakes Erie and Ontario. The water carries plastics from one lake to the next, compounding the concentration each time, Mason said.
That her team found plastic pollution was unsurprising, but Mason was surprised by the volume, and even more by the kind of plastic it found.
"The reigning kind of thinking is that plastic moves from the land to the ocean through rivers and lakes, and that it gets smaller as it goes through erosion," Mason said. "We thought we would find bigger pieces in the lakes than in the ocean, but we didn't really. The vast majority of what we found was really, really small."
The project found mostly microplastics, pieces less than 13/64ths of an inch. Such fragments are much smaller than those expected.
Why larger pieces were not more common baffles researchers.
"You don't find microplastic in the ocean like we did in the lakes," Mason said. "Somewhere in between there it disappears, and we want to know where it's going."
The researchers think that the microplastics could be washing up on beaches, or may be entering the food chain if consumed by microorganisms or fish. "There's this uncertainty right now, so one of the next things we have to do is get out on a boat and look at the food chain to see if the plastic shows up," Mason said.
Plastic in the food chain presents a serious human health threat, Mason said, because many non-plastic pollutants, known as persistent organic pollutants, latch onto plastics in the water, which could then be consumed by aquatic life.
"All those chemicals leach from the plastic into the fat of the fish," Mason said. "This has both direct ways of harming the fish, such as lining their intestines and interfering with their ability to absorb nutrients from food, and indirect ones.
"The fish may not immediately die, but they could remain toxic, and that's really scary. If the plastics and chemicals are moving into the food chain, they're moving into us."
Scientists and the plastics industry recognize the dangers of plastic in the aquatic ecosystem. According to the American Chemistry Council, a Washington-based national trade association representing a chemistry firms including plastic manufacturers, any human debris is potentially destructive to the lakes.
"Discarded or littered items of any material, whether plastic, paper, steel or aluminum, doesn't belong in the marine ecosystem," said Allyson Wilson, a council communications representative. "Litter can absolutely pose a threat to marine life when animals get entangled, trapped or mistake plastics for food."
Wilson added, however, that microplastics like those found by Mason could be less harmful than many scientists fear. "This is an emerging area of research, and we're all committed to better understanding microplastic's effects on the marine environment," she said. Some research indicates that persistent organic pollutants may bond so tightly to the plastic that they cannot be separated and digested by the fish.
Wilson noted that the Food and Drug Administration requires health and safety inspections of commercial fish catches, and that the Environmental Protection Agency regulates drinking water and requires water treatment facilities to filter particles from the water.
Further study of plastic in the Great Lakes is necessary before concerns over it can be dismissed, Mason said. Her study plays into the larger goals of the Los Angeles-based 5 Gyres Institute, an environmental group that studies the causes and impacts of plastic pollution in the oceans, specifically in five subtropical gyres. A gyre is a large area of rotating ocean currents in which plastics accumulate.
Having studied each of the five gyres, the institute is now turning its attention inland toward the sources of the pollution.
"Most plastics that end up in the ocean start out on land," said Marcus Eriksen, co-founder of 5 Gyres. "This project is us going upstream from the oceans and trying to trace them back to their origins."
Great Lakes pollution has global consequences, Eriksen said.
"The gyres we study account for about 25 percent of the planet's surface, and they draw pollution from all over the world, including the Great Lakes. They're covered in a thin layer of plastic soup," he said.
It would be a waste of time and money to try to clean up all the plastic in the gyres, he said. Identifying and reducing that pollution at its sources upstream is the only way to reduce it.
"No amount of plastic in the lakes is acceptable," Mason said. "The best cure is to find ways to reduce plastic use. We're all part of the problem, and that means we're all part of the solution. If we change our consumer habits, we change what's in the water."
Next summer, the project aims to continue the research on Lake Michigan.