Conventional plastics, which are based on fossil oil, have flooded the Earth, and there are microplastics in all living things. This has led to an intense search for alternatives that degrade faster in nature. Sugarcane-based biopolymers are one such option. The most common type of bioplastic is poly-L-lactide (PLA), which is used in 3D printers, textiles, food packaging, disposable tableware, and other applications.
Bioplastics also have a negative impact on biological life. PhD student Azura König-Kardgar at the University of Gothenburg found that the behavior of baby chick exposed to bioplastics in fish food changed over a six-month period. They reacted a lot more when they met a fellow perch than usual. In addition, there were signs of decreased locomotion, altered ability to form shoals, and altered reaction when approaching danger.
“Toxicological experiments that analyze animal behavior are very rare. Most commonly, researchers look at physiological changes. We can see that something in the PLA plastic is causing changes in the fish, but we can’t see what,” Azurra says.
Since this research looked at PLA microplastics, the researchers also tested feeding the chick particles of kaolin, a white clay used in porcelain and paper coatings. The kaolin-fed fish showed some subtle changes in behaviour. However, the male hormone was affected and some other gene expressions were repressed in the fish, such as the response to stress.
“Our view is that PLA is not harmful to fish, so it should not be sold as an environmentally friendly alternative to regular plastic. It should be considered equivalent to regular plastic,” Azurra says.
The fish were fed for six months with food containing 2 percent PLA, which is a concentrate of the normal petrochemical plastic used in previous studies. The amount of kaolin fed to another group of fish was 2 percent. In addition, there was also a control group of perch fed uncontaminated food.
Publication of the research in the journal macroenvironmental science.
Azora König Kardgar et al, Chronic poly(β-lactide) (PLA)-microplastic ingestion affects the social behavior of juvenile European fish (Pirca fluviatilis), macroenvironmental science (2023). DOI: 10.1016/j.scitotenv.2023.163425
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