BLOOMFIELD HILLS, MICH. — Microplastic particles, not just in the form of tiny beads but fibers and fragments, too, are polluting the Great Lakes and launching new areas of study for scientists.
From face scrubs to fleece jackets, the list of threats to the five lakes, which hold about 20 percent of the earth's surface freshwater, is growing. The latest concerns are polymer particles under 5 millimeters in size, and there are calls to start scrutinizing water samples for nanoplastics under 0.33 mm.
Overall, the Great Lakes studies to date just scratch the surface of the problems polymers could be posing, according to Jennifer Daley, a research fellow at the University of Michigan.
“What we saw most were polyethylene, polypropylene or nylons, which makes sense because these dominate plastics production,” Daley said during a March 6 lecture at the Cranbrook Institute of Science in Bloomfield Hills.
Cranbrook has an exhibit called “Plastic Waters: From the Great Lakes to the Oceans,” which is being presented by the Alliance for the Great Lakes and the California-based 5 Gyres Institute.
Known for tracking an estimated 260,000 metric tons of floating debris (the weight of an estimated 5.2 billion plastic particles) that accumulated in five ocean zones, 5 Gyres has brought attention to the derelict fishing nets, shopping bags, action figures, bottle caps, flip flops, pacifiers and more swirling about the Pacific, Atlantic and Indian oceans.
Daley said the soupy salt waters peppered with macroplastics — as high as 10 particles per liter in one study of the northeast Pacific — gave rise to questions about synthetic threats to other waterways.
“In the last few years people have been asking: What about fresh water systems, particularly the Great Lakes,” Daley said. “They're host to 30 million people, 21 percent of our fresh water, and $4 billion in fishing alone. When you have that many people on a system, there are bound to be stressors. The Great Lakes are impacted by everything from habitat alteration and invasive species to pesticides and litter. Where does plastic pollution fit when it comes to Great Lakes stressors?”
The answers are only starting to come into focus on microscope slides.
Too much fiber
One recent threat to make waves in the mass media came in January with coverage of water samples taken in 2013 from Lake Michigan. Scientists sounded the alarm that 12 percent of the debris consisted of microfibers.
“To be honest, most microfibers are probably coming from our washing machines,” Daley said of fabrics made from plastics like polyester and nylon.
Microfibers also were found in the gastrointestinal tracts of some fish and a double-crested cormorant, which eats fish.
Another field study, this time of 100 fish by University of Michigan researchers, showed similar results for the five species of fish tested.
“While they didn't find microbeads, they did find fibers in 11 to 36 percent of the fish,” Daley said.
Scientists now are trying to determine the risks posed by the fine fibers on aquatic life along with the effects from highly publicized microbeads and small fragments from degrading macroplastics.
“This is an area where we really need to study to understand which organisms are coming into contact the most with microplastics,” Daley said. “This could be ingestion by zoo plankton that swim across the waters or ingestion by fishes. In terms of effects, we don't know at this point but these are some areas we think could be a concern if indeed organisms are taking up microplastics to a significant degree.”
One of the 5 Gyres exhibit pieces at Cranbrook shows a picture of a gutted fish next to about 15 little shards of blue, yellow, white, black, beige and brown plastic. The caption asks: What's in your sushi?
Scientists have a lot of other questions about the effects of microplastic litter in the marine environment.
“This is an area we're getting into now,” Daley said. “We're early in the stages of understanding the impact on organisms. We know microplastics are small enough to be taken up by a number of organisms across all trophic levels.”
A trophic level is the position an organism occupies in a food chain. Daley said in 2013, scientists saw the uptake of microplastics in one of the bottom feeders change the energy reserve of marine worms.
“There was a 30 percent decrease in energy reserves in worms from a 1 percent by weight microplastics ingestion,” she said. “What that shows is there might be an issue with starvation if there's that substantial of a decrease in energy reserves. We need field validations to see what this looks like at environmental concentrations.”
As a physical contaminant of organisms, Daley showed a slide that says ingested microplastics could have both behavioral and morphological effects. They could hinder mobility, reduce vigor, block intestines and gastric enzyme secretions, diminish feeding stimulus, hamper breathing and delay ovulation.
Then, there are the chemical contaminants. Some research suggests aquatic organisms also are exposed to the chemicals associated with plastics.
“This is all really early research and we need to do more work,” Daley said.