• Microplastic pollution is a source of growing concern in the Great Lakes region.
• New research looks at how that pollution affects a fish throughout its entire life cycle.
• Plastic collected from the environment versus directly from manufacturers seems to have more dire effects on fathead minnow reproduction.
Research on how microplastics might be affecting wildlife has exploded in recent years. But most studies only expose animals to the pollution for one portion of their life.
Some researchers think that approach might not be telling the full story.
“A fish isn’t fully grown in pristine water, and then all of a sudden gets exposed to microplastics,” said Kennedy Bucci, a former Ph.D. student at the University of Toronto. “They’re exposed to microplastics for their entire life. … That’s why, to me, it was really important to do this longer term study.”
Bucci did what relatively few studies have done so far: Exposed a fish — fathead minnows in this case — to microplastics for their entire life cycle, from the time they were eggs, to the time they reproduced.
Fathead minnows are a common prey fish found across the Great Lakes region. They have a relatively short lifespan, which makes them easier to study in a lab setting. Plus, Bucci says, they’re a hardy species.
But she also wanted to look at how different plastics might affect the minnows differently.
“A lot of times studies tend to just use the plastic that's coming from the manufacturer because it's easier to get,” she said. “But it actually lacks a lot of chemical diversity compared to the ones that we collect from the environment.”
She says that’s because the plastics already floating around have had time to absorb different chemicals and environmental pollutants.
So she exposed one group of fish to pre-consumer plastic purchased directly from manufacturers, and another group to environmental plastic she collected from the shores of Lake Ontario.
“I made sure they were all the same color. They were all the same type,” Bucci said. “Then I put them in a coffee grinder and ground them up into almost like a powder.”
She sieved them to make sure they were all the same size. “And then we literally just dumped them into the tanks at a known concentration – just sprinkled them into the tanks with the fish,” she said.
And she found major differences in the minnows exposed to the ground up microplastic from Lake Ontario.
Both groups had physical stress, but in the environmental plastic group, “we also saw effects that indicated endocrine disruption,” Bucci said. “They began reproducing a little later, and the main thing was that their eggs were more fragile than the eggs of the other treatment and control.”
When she tried counting the eggs, they broke easily. So she decided to measure them.
“And we found the eggshells were actually significantly thinner in the fish that were exposed to microplastics from Lake Ontario,” she said.
And the new generation of minnows that hatched from those thinner eggshells? They had much higher rates of deformity.
“Some fluid buildup. There [were] skeletal abnormalities, so the tail might be kind of an L-shape instead of … straight,” Bucci said. “One of the big ones we saw was called pin eyes. The eyes on a larval fish are pretty big compared to their body size, and then in the pin-eyed fish, their eyes were really small.”
She says that’s likely because of the contaminants environmental plastics have had time to absorb — things like heavy metals, pharmaceuticals and toxic chemicals.
Bucci says all of these reproductive impacts could potentially have a cascading effect.
“In future generations, there might be fewer fathead minnows … swimming around, which would affect their predators,” she said.
The minnows are prey to a number of important sport-fishing species in the Great Lakes region, like walleye, yellow perch and largemouth bass.
Microplastics have been found in every Great Lake, and it’s not unusual for researchers to find hundreds of pieces of plastic in fish.
“It is a really broad issue,” Bucci said. “The fact that I chose to collect the plastic from Lake Ontario – it’s not to say that it’s not happening in other Great Lakes.”
And she says there’s a need for more studies on the effects of environmental microplastics specifically.
“I think what [this study] tells us is that the chemical component of microplastics is actually really important. A fish isn't exposed to just the physical stress associated with the plastic, it also carries all these chemicals … that cause effects we might not be expecting to see,” Bucci said. “Our idea of what the effects of microplastics are might not be telling the whole story, because we haven't explored the chemical component as much as I think we should be.”
