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Microplastic pollution induces algae blooms in experimental ponds but bioplastics are less harmful
Summary
A three-month outdoor pond experiment found that high concentrations of petroleum-derived polyurethane microplastics consistently triggered harmful algal blooms by suppressing the zooplankton that normally graze on algae, while two biodegradable bioplastic alternatives caused far smaller ecological disruptions. This is one of the first studies to link microplastic pollution directly to eutrophication—a growing global water quality crisis—suggesting plastics may be an underappreciated contributor to algal bloom frequency. The findings also suggest that biodegradable plastics could meaningfully reduce ecosystem impact compared to conventional synthetics.
An ever-growing sea of plastic waste permeates even the most remote ecosystems; however, its ecological impact is unclear. Less persistent bioplastic alternatives are available but also have unknown environmental effects. We conducted a three-month experiment exposing plankton in experimental ponds to 10 concentrations of three different thermoplastic polyurethane microplastics, including two biodegradable bioplastics. Algal blooms with dense chlorophyll occurred consistently at high concentrations of the petroleum-derived thermoplastic polyurethane, but only occasionally with the two bioplastics. Herbivorous zooplankton density was strongly reduced by typical thermoplastic polyurethane and only weakly by bioplastics, therefore the effect on algae is at least partly due to reductions in top-down grazing pressure. Microbial communities exhibited compositional shifts in response to all three plastic types, with petroleum-derived plastic associated with the most pronounced differences across both prokaryotic and eukaryotic domains. Our results show that plastic pollution may contribute to the growing global problems of eutrophication, coastal hypoxia and harmful algae blooms, and that biodegradable plastics may have smaller environmental footprints.
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