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Different mulch films, consistent results: soil fauna responses to microplastic
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Scientists compared how conventional polyethylene and biodegradable PLA/PBAT microplastics affect earthworms and springtails in soil over 28 days. Neither plastic type significantly harmed reproduction, but subtle cellular stress responses were detected, and the effects were similar for both conventional and biodegradable plastics, suggesting that biodegradable alternatives may not be safer for soil organisms.
Agricultural activities contribute to plastic pollution, with unintentional introduction and intentional use of plastic mulch films leading to the accumulation of microplastic particles in soils. The lack of removal techniques and scarce information on the effects on soil organisms, especially for biodegradable mulch films, necessitate an assessment of potential effects. This study aimed to elucidate the effects of mulch film microplastic on soil fauna by investigating reproduction output and subcellular responses before and after recovery from exposure. Two common soil organisms, Folsomia candida and Eisenia fetida, were exposed to petroleum-based polyethylene (PE) and biodegradable polylactic acid/polybutylene adipate terephthalate (PLA/PBAT) microplastic for 28 days, according to OECD guidelines 232 and 222, respectively. Juvenile numbers revealed no polymer- or concentration-dependent effects on E. fetida and F. candida reproduction after exposure to up to 5 and 10 g/kg soil, respectively. To provide a more sensitive and early indication of sublethal effects, subcellular responses in E. fetida were analyzed. Glutathione S-transferase (GST) activity increased with rising microplastic concentration; however, catalase (CAT), acetylcholine esterase (AChE) activity, and reactive oxygen species (ROS) did not differ from control levels. Further, the more environmentally relevant PE polymer was chosen for in-depth assessment of subcellular response after 28-day microplastic exposure and subsequent 28 days in uncontaminated soil with E. fetida. No significant differences in biomarker activity and stress levels were observed. We conclude that mulch film-derived microplastic did not adversely affect earthworm and collembolan species in this scenario, except for a slight induction in the detoxification enzyme glutathione S-transferase.
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The impact of microplastic on nematodes: Soil type, plastic amount and aging as determinants for the fitness of Caenorhabditis elegans
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Researchers tested how two types of microplastics, conventional polyethylene and biodegradable PLA/PBAT, affected tiny soil worms called nematodes across different soil types. Conventional plastic at high concentrations reduced worm reproduction and growth, while the biodegradable plastic caused no harm. Importantly, as microplastics aged in the soil over time, their negative effects worsened, suggesting the long-term impact of plastic pollution in agricultural soil may be greater than short-term studies indicate.
Ecotoxicological effects of soil microplastic types and concentrations on earthworms
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Researchers tested the effects of conventional polyethylene and polypropylene microplastics alongside biodegradable PBAT microplastics on earthworms over 28 days. They found that PP microplastics caused significant mortality at the highest concentration, while PBAT, despite being marketed as biodegradable, induced the highest levels of DNA damage and cellular stress. The study suggests that biodegradable plastics are not necessarily less harmful to soil organisms than conventional plastics.
Response of terrestrial crustacean Porcellio scaber and mealworm Tenebrio molitor to non-degradable and biodegradable fossil-based mulching film microplastics
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Researchers tested how two soil organisms, woodlice and mealworms, responded to microplastics from both conventional polyethylene and biodegradable mulching films used in farming. Both types of microplastics affected the organisms' gut bacteria and caused stress, though the effects varied by plastic type. The study challenges the assumption that biodegradable farm films are completely safe, since their microplastic fragments can still harm soil organisms important for healthy agricultural ecosystems.
Effects of conventional versus biodegradable microplastic exposure on oxidative stress and gut microorganisms in earthworms: A comparison with two different soils
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Researchers compared the toxic effects of conventional polyethylene and biodegradable polylactic acid microplastics on earthworms in two different soil types. Both types of microplastic caused oxidative stress and altered gut microbiota in earthworms, with toxicity increasing at higher concentrations. The study found that microplastic concentration was more important than the type of plastic or soil in determining the level of harm, and that biodegradable plastics were not necessarily safer for soil organisms.
Toxicity comparison of multiple biodegradable and conventional microplastics on earthworms: Ingestion, tissue damage, oxidative stress, and transcriptional responses
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This study compared the toxicity of four biodegradable microplastics and conventional polyethylene microplastics on earthworms across multiple biological endpoints. Researchers found that biodegradable microplastics caused tissue damage, oxidative stress, and altered gene expression at levels comparable to or sometimes exceeding conventional plastics, challenging the assumption that biodegradable alternatives are inherently safer for soil organisms.
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