European researchers have discovered that larval fish love to gobble up plastic microbeads, which stunts their growth and makes them more vulnerable to predators. It's yet another reason to ban these awful materials and to limit the amount of plastic entering into our lakes and oceans. Damselfish larvae that has ingested microplastic particles (Image: Oona M. Lönnstedt)
As reported in a new Science study, developing fish that are exposed to high concentrations of microplastic particles exhibit altered behaviours and stunted growth that lead to increased mortality rates. After exposure, baby fish became smaller, slower and more susceptible to predators. Part of the problem, say the Uppsala researchers who led the work, is that larval fish are actually preferring the microplastic in favour of their natural food source. They're literally getting hooked on this stuff as it were junk food.
These tiny bits of badness come from plastic that has been either manufactured that way (that is, microbeads) or from larger bits of plastic that have broken down. Microbeads measure about 5-10 micrometres across and are often found in cosmetics and personal care products, such as lipstick, mascara, facial cleansers, toothpaste and other similar products. Microbeads are also used in biomedical and health science research. Regular-sized chunks of plastic start to break down when exposed to UV radiation, chemical degradation and the movement of waves. Eight million tonnes of plastic enters into our oceans each year, making this a serious environmental problem.
Microbeads, because they're so small, often pass through sewage treatment plants without being filtered out. These plastic orbs then make their way into rivers, canals, oceans — and eventually into the bellies of developing fish larvae.
A young perch that has ingested microplastic particles (image: Oona M. Lönnstedt)
To learn how plastic might affect marine animals, a Swedish research team led by Oona M. Lönnstedt exposed fish larvae to varying concentrations of microplastic (namely polystyrene) in aquariums. Their findings suggest that microplastic particles operate both chemically and physically on larval fish performance and development.
Eggs exposed to microplastics decreased hatching success by about 15 per cent. Those who did emerge were "smaller, slower, and more stupid" than those that hatched in clean water, noted Lönnstedt in a BBC article. These fish also fared very poorly when exposed to predators; exposed two-week-old larvae were much less able to escape predation.
Disturbingly, the researchers discovered that the presence of the plastic also changed the food preferences of the exposed fish. Larval perch that had access to microplastic particles only ate plastic, while completely ignoring their natural food source of free-swimming zooplankton. The researchers say there's probably a chemical or physical cue emitted by the plastic that triggers a feeding response in the fish.
"This is the first time an animal has been found to preferentially feed on plastic particles and is cause for concern," noted Peter Eklöv, the co-author of the study.
Pike that has ingested microplastic particles (Image: Oona M. Lönnstedt)
These findings highlight the need for new management strategies or alternative biodegradable products that lowers the release of microplastic waste products. In the US, the Microbead-Free Waters Act of 2015 prohibits the manufacture and introduction of rinse-off cosmetics that contain plastic microbeads. Australian cosmetic companies are currently undergoing a voluntarily phase-out of microbeads, however Minister for Environment Greg Hunt has stated that he will seek to ban them by law if the phase-out does not appear to be achieving "what is effectively a widespread ban on microbeads". Canada and Europe are behind and clearly need to do the same.