Insect larvae can contribute to microplastic

image: For the study, the researchers presented the larvae with pieces of plastic film cut from a commercially available biodegradable plastic bag, alongside pieces of oak leaf.
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Credit: Katey Valentine, University of York

A common insect larva may be inadvertently contributing to microplastic pollution of our rivers and waterways by chewing on trash, according to a new study.

Researchers from the University of York have examined how caddisfly larvae – a common insect that inhabits freshwater environments around the world, such as rivers, lakes and ponds – interact with litter plastics.

They found that the larvae use their sharp teeth to bite off the plastic into small pieces, which they then use to build the protective casing they live in until they are ready to turn into adult flies.

Although they presented the larvae with many alternative natural building materials, the researchers observed them choosing to gnaw through plastic film, generating hundreds of microplastic particles within days.

Microplastics are tiny fragments of plastic that often form from the breakdown of larger plastic waste. Scientists have found microplastics everywhere they have looked, including in the ice of Antarctica, in the deep oceans, in seashells, in drinking water, in rain, and drifting through the air we let’s breathe.

Scientists do not yet know if these particles are dangerous, but the risks are considered high.

The study’s lead author, PhD student Katey Valentine from the University of York’s Department of Environment and Geography, said: “Given growing concern about the effects of plastic pollution on our environment, we wanted to understand if caddisfly larvae would interact with objects. plastic waste that commonly pollutes the environment, and determine what the consequences of these interactions might be.

“The active use of plastic waste by freshwater animals that our study revealed could contribute to the formation of microplastics in these habitats. Further work is now needed to determine the extent to which these animals might use plastic waste and create microplastics in natural freshwater environments globally, and whether other common freshwater species exhibit similar behavior. similar.

Caddisfly larvae typically use natural materials such as sand, gravel, and plant debris to construct their protective envelopes, weaving pieces together using self-produced silk.

For the study, the researchers presented the larvae with pieces of plastic film cut from a commercially available biodegradable plastic bag, along with pieces of oak leaf. Although the larvae generally tended to use more oak leaves, many larvae used pieces of plastic to construct their new casing while leaving the appropriate leaf pieces intact.

The plastic film used for the experiment was made from a bio-based polyester traditionally marketed as a biodegradable alternative to conventional plastic – leading to its increased use in food packaging and agricultural mulching films as “ecological” alternative.

However, although it is biodegradable in industrial composting systems, in aquatic environments, the degradation of this plastic would be extremely slow and therefore it is believed to pose a pollution risk similar to that of conventional plastics.

Study co-author Professor Alistair Boxall, from the Department of Environment and Geography, said: “As well as demonstrating the production of microplastics, our work also shows how these organisms can exploit plastics to build their houses. This could make the larvae more prone to predation and lead to increased exposure to things like additives that will slowly leak out of the plastic.

Caddisfly larvae are a driver of plastic waste degradation and microplastic formation in freshwater environments is published in the Journal Environmental toxicology and chemistry.

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