A damselfish larva after it has ingested microplastic particles. | Oona Lönnstedt
Editor's Note: On May 3, 2017, Science retracted the June 3, 2016 Report “Environmentally relevant concentrations of microplastic particles influence larval fish ecology” on which the story below was based. The full retraction statement from Science Editor-in-Chief Jeremy Berg can be found here: http://science.sciencemag.org/cgi/doi/10.1126/science.aan5763
Exposure to high concentrations of plastic particles inhibits hatching, decreases growth rates, and alters feeding preferences of European perch larvae, a new study in the 3 June issue of Science shows. It also prevents the perch from responding to predatory cues.
"Our results demonstrate that microplastic particles not only affect an animal's physiology," said study co-author Oona M. Lönnstedt, a postdoctoral research fellow in the department of ecology and genetics at Uppsala University, "but also its natural behaviors, such as feeding choices, activity rates, and predator avoidance strategies."
Earlier studies of microplastics' effects on fish have mostly looked at adverse physiological effects, like the way consumption of tiny plastics depletes levels of the glycogen stored in the liver for energy or increases fat cell levels.
"If microplastics are indeed affecting organisms in this way, both chemically and physically," said Lönnstedt, "this really does call for a ban on microplastic beads in personal care products. It also highlights the need to replace plastic products with biodegradable options."
Because of the massive use of plastics in modern society, plastic waste is accumulating in large quantities, often ending up in waterways. Much of this debris is in the form of microplastics, plastic fragments less than five millimeters in all dimensions that either break down from larger pieces of debris or are manufactured that way (in the tiny beads in face wash products, for example).
While hundreds of studies have demonstrated global microplastic contamination, few have investigated its impacts on animal populations, communities, and ecosystems. "This pattern is not unique," Chelsea M. Rochman, the David H. Smith Conservation Research Postdoctoral Fellow at University of California, Davis, writes in a related Perspective article. "For many chemical contaminants in the environment, widespread contamination is documented, yet little is known about their ecological impacts."
The mechanisms by which microplastics impact eggs, embryos, and larvae of aquatic organisms, which are particularly vulnerable to water-borne pollutants, are especially murky.
"No one has ever looked at direct effects of microplastic particles on fish development," said Lönnstedt.
Microplastic particles ingested by a larval perch fish line its stomach.| Oona Lönnstedt
To provide greater insights into this problem, she and fellow co-author Peter Eklöv, also in the department of ecology and genetics at Uppsala University, collected European perch embryos and larvae from the Baltic Sea. In lab aquaria, they exposed these specimens to varying concentrations of polystyrene microplastics, including very high concentrations comparable to those found in nature.
The biggest surprise in observing the fish, Lönnstedt said, was the fact that they preferentially ate microplastic particles. "I remember looking at them under the microscope and just seeing so many little plastic pieces in their stomachs, for fish after fish. It was terrifying."
Among other results, she and Eklöv observed that exposure of embryos to microplastics decreased hatching success by about 15%. What's more, exposed 2-week-old larvae were much less able to escape predation when exposed to predator fish in the same tank, leading to reduced survival. Finally, fish reared in the highest microplastic concentrations were significantly smaller than fish reared in average concentrations.
The results with the European perch will translate to many other fish types, Lönnstedt explained.
"Since this study, I have done similar experiments with other species of fish, both tropical [damselfish] and temperate [pike and flounder], and all seem to respond in a very similar manner to microplastic particles."
The next step is to do these studies with several different plastic polymers, said Lönnstedt. "Now we know that polystyrene is bad, but we also need to compare it to the other common polymers, such as polyethylene and PVC."
Studies like Lönnstedt's could guide efforts to mitigate the entry of microplastics into the oceans by determining the types that may be most hazardous and by identifying the most sensitive populations, species, and ecosystems. "With such data in hand," Rochman writes, "practitioners can shift their energy toward prevention and avoid the need for costly recovery and restoration."