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The chronic effects of polyethylene terephthalate and biodegradable polyhydroxybutyrate microplastics on Daphnia magna
Summary
Researchers compared the effects of conventional PET microplastics and biodegradable PHB microplastics on water fleas over 26 days. PET fibers and fragments caused significant harm, reducing swimming speed by 20% and survival to just 20%, while PHB particles showed no negative effects, with survival and mobility comparable to control groups. The findings suggest that biodegradable polymers like PHB could be a safer alternative to conventional plastics for reducing harm to aquatic organisms.
The inappropriate disposal of plastic materials and their slow decomposition into microplastics (MP) pollutes aquatic ecosystems, leading to toxic effects on organisms. MP can have different shapes and be made from different polymeric materials; being carbon-based polymers the common ones. The toxicity associated with such MP has led to the need to search for alternative polymers with faster degradation times. Biodegradable polymers such as polyhydroxybutyrate (PHB) are promising substitutes for synthetic polymers. In this work, the environmental impact of PHB was determined and compared to that of polyethylene terephthalate (PET). For this purpose, the model organism Daphnia magna was used in a 26-day experiment. The toxic effects of MPs was assessed by analysing the survival, the swimming velocity and the filtration rate of Daphnia magna. After 21 days of exposure, PET in the form of fibers or fragments caused the most toxicity, resulting in a 20% decrease in swimming velocity and a 20% of Daphnia magna survival. However, after 21 days, PHB resulted in 80% survival, which is comparable to control experiments, and Daphnia magna showed mobility that was comparable to that seen for control experiments. Therefore, with the presence of food PHB microplastic particles had no negative effects on Daphnia magna. Considering these results, PHB might be a promising material as a substitute of conventional polymers.