Microplastics stunting growth of worms

Commonly used plastics can affect earthworms, plant growth and the pH of soil, finds a new study.

New research from Anglia Ruskin University has found that the presence of microplastics can stunt the growth of earthworms, which could have a serious impact on the soil ecosystem.

The researchers examined the impact of biodegradable polylactic acid (PLA), high-density polyethylene (HDEPL) and microplastic clothing fibres (acrylic and nylon) on earthworms living in the soil as well as ryegrass sown on top.

Their study showed that after a period of 30 days in the presence of HDPE, which is commonly used in the production of plastic bottles and tote bags, earthworms lost on average 3.1% of their weight.

In comparison, earthworms living in control conditions without added microplastics saw their weight increase by 5.1% over the same period.

The study also found that the presence of HDPE led to a decrease in the soil pH. What’s more, soil containing PLA, a biodegradable form of plastic, reduced shoot height of ryegrass, while both PLA and clothing fibres led to fewer ryegrass seeds germinating.

“Earthworms can be called ‘ecosystem engineers’ as they help maintain a healthy soil. They do this through ingesting dead organic matter, therefore contributing to the availability of nutrients,” said Connor Russel, co-author of the study.

“Their burrowing activity improves soil structure, helping with drainage and preventing erosion. It’s therefore highly likely that any pollution that impacts the health of soil fauna, such as earthworms, may have cascading effects on other aspects of the soil ecosystem, such as plant growth.”

While the researchers do not yet know the specific reasons for the weight loss in earthworms, they suspect that it could be because microplastics obstruct and irritate the digestive tract, which limits the absorption of nutrients and reduces growth.

Image credit: USDA NRCS South Dakota via Flickr

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