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Earthworms mediate the influence of polyethylene (PE) and polylactic acid (PLA) microplastics on soil bacterial communities
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Researchers studied how earthworms interact with both conventional polyethylene and biodegradable PLA microplastics in soil over 120 days. Both types of microplastics changed the composition of soil bacterial communities, but in different ways, and earthworms appeared to mediate these effects by consuming bacteria or altering soil conditions. The findings show that even biodegradable plastics disrupt soil ecosystems, and that soil organisms play a complex role in how microplastics affect the underground environment.
There is a growing body of evidence that suggests that both biodegradable and conventional (non-degradable) microplastics (MP) are hazardous to soil health by affecting the delivery of key ecological functions such as litter decomposition, nutrient cycling and water retention. Specifically, soil fauna may be harmed by the presence of MPs while also being involved in their disintegration, degradation, migration and transfer in soil. Therefore, a comprehensive understanding of the interactions between MPs and soil fauna is essential. Here, we conducted a 120-day soil microcosm experiment applying polyethylene (PE) and polylactic acid (PLA), in the absence/presence of the earthworm Eisenia nordenskioldi to estimate the relative singular and combined impact of MPs and earthworms on the soil bacterial community. Our findings revealed contrasting effects of PE and PLA on the composition and diversity of soil bacteria. All treatments affected the community and network structure of the soil bacterial community. Compared to the control (no MPs or earthworms), PE decreased bacterial alpha diversity, while PLA increased it. Patescibacteria were found to be significantly abundant in the PE group whereas Actinobacteria and Gemmatimonadetes were more abundant in PE, and PLA and earthworms groups. The presence of earthworms appeared to mediate the impact of PE/PLA on soil bacteria, potentially through bacterial consumption or by altering soil properties (e.g., pH, aeration, C availability). Earthworm presence also appeared to promote the chemical aging of PLA. Collectively, our results provide novel insights into the soil-fauna-driven impact of degradable/nondegradable MPs exposure on the long-term environmental risks associated with soil microorganisms.
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Soil application of PE and PLA microplastics alter earthworm (Eisenia nordenskioldi) gut bacterial community and soil microbiome-metabolome dynamics
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Researchers compared the effects of conventional polyethylene and biodegradable polylactic acid microplastics on earthworm gut bacteria and soil ecosystems over 120 days. They found that polyethylene had a more significant impact on soil microbial communities and metabolic processes than PLA at environmentally relevant concentrations. The study highlights that both types of microplastics can alter soil ecosystems, but conventional plastics may pose greater ecological risks.
Earthworms Exposed to Polyethylene and Biodegradable Microplastics in Soil: Microplastic Characterization and Microbial Community Analysis
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Researchers exposed earthworms to biodegradable and conventional polyethylene microplastics in natural soil and found that worms ingested both types. The biodegradable plastic showed signs of partial breakdown in the earthworm gut, while conventional polyethylene remained unchanged. Although microplastics did not significantly alter the soil or gut microbiome in this study, the results confirm that earthworms transport microplastics through soil ecosystems.
Earthworms alleviate microplastics stress on soil microbial and protist communities
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Researchers found that earthworms can help alleviate the negative effects of microplastic pollution on soil microbial and protist communities. In microcosm experiments, soils with earthworms showed more resilient bacterial, fungal, and protist communities when exposed to both conventional and biodegradable microplastics. The study suggests that soil macrofauna play an important role in buffering ecosystems against the disruptive effects of microplastic contamination.
The plastisphere of biodegradable and conventional microplastics from residues exhibit distinct microbial structure, network and function in plastic-mulching farmland
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Researchers compared the bacterial communities that colonize biodegradable and conventional plastic microplastics in farmland soil. They found that biodegradable plastics (PBAT/PLA) and conventional polyethylene each attracted distinct microbial communities with different functions, including bacteria that could degrade plastics or cycle nutrients. The results suggest that even biodegradable plastics create unique microbial environments in soil that may affect soil health and function in unexpected ways.
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.
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