Mosquitoes eating microplastics are contaminating other food chains

20 Sep 2018

Image: 7th Son Studio/Shutterstock

Mosquito larvae could exacerbate the plastic contamination problem even as they become adult flies.

While there are numerous ways plastic contamination can affect the world we live in, researchers at the University of Reading have found a previously unknown pathway that plastic is taking to pollute the environment and enter the food chain.

Scientists at the university found that microplastics consumed by mosquito larvae remain in the mosquito through metamorphosis to a non-feeding pupa and then as an adult. Predators such as birds and bats eat these insects, presenting an alarming new avenue for microplastics to enter the food chain. The study was published in Biology Letters.

Microplastics and general plastic pollution is a fast-growing problem people are becoming much more conscious of. Microplastics originate from plastic pollution, which takes centuries to break down. These plastics are widespread in oceans and freshwater all over the world.

Microbeads in cosmetic products also contribute to the problem as aquatic organisms eat these, allowing them to enter into the food chain and other creatures such as fish.

Mosquitoes unwittingly exacerbating plastic pollution

Lead author of the study, Prof Amanda Callaghan, said that while there is public awareness of microplastics in water, the problem also extends to the sky above us. She said: “This is eye-opening research, which has shown us for the first time that microplastics are able to navigate several life stages in flying insects, allowing them to contaminate all kinds of living creatures who would not normally be exposed to them.

“It is a shocking reality that plastic is contaminating almost every corner of the environment and its ecosystems.”

Callaghan’s research team fed 150 aquatic mosquito larvae a mixture of food and microbeads of different sizes. They examined 15 randomly selected ones when the insects were still in the larval stage; they then looked at another 15 when the creatures had reached the adult phase. All 30 individual insects had microplastics present in their bodies.

On average, a larva contained more than 3,000 two-micrometre-wide beads. As the mosquitoes grew, they gradually stopped consuming the microplastics and excreted many of the beads. This is because the larvae are filter feeders and they cannot distinguish between a piece of plastic and a piece of food.

Even with the reduction of microbeads ingested over time, the researchers counted approximately 40 beads on average in adults. Callaghan added: “Any organism that feeds on terrestrial life phases of freshwater insects could be impacted by microplastics found in aquatic ecosystems.”

The researchers are now examining if the consumption of the plastics harms mosquitoes.

Ellen Tannam was a journalist with Silicon Republic, covering all manner of business and tech subjects