Science

New study suggests corals eat plastic because they like the taste

Scientists believe chemicals in plastic could be acting as a stimulant.

Corals like to eat plastic because it tastes good, scientists have found, raising concerns about the hazardous effect it might have on these marine animals.

New research from Duke University has revealed that unlike other sea creatures who mistakenly eat plastic debris because it looks like prey, corals consume plastic because it “just plain tastes good”.

Corals have no eyes, which means there are no enticing visual cues to make tiny bits of plastic look like food.

Scientists have also found that the corals prefer microbe-free microplastics – suggesting there may be chemicals in the plastic itself that makes it tasty.

Austin S Allen, a PhD student at Duke’s Nicholas School of the Environment, said: “Corals in our experiments ate all types of plastics but preferred unfouled microplastics by a threefold difference over microplastics covered in bacteria.

“This suggests the plastic itself contains something that makes it tasty.”

Alexander C Seymour, a geographic information systems analyst at Duke’s Marine Robotics and Remote Sensing Centre who co-led the study, said: “When plastic comes from the factory, it has hundreds of chemical additives on it.

“Any one of these chemicals or a combination of them could be acting as a stimulant that makes plastic appealing to corals.”

This behaviour has the researchers concerned because plastic cannot be digested.

It means there is a high risk of intestinal blockage to the animals who consume it, creating a false sense of fullness and, consequently, depriving them of adequate access to sources of nutrition and energy.

Corals eating plastic.
A coral polyp ingesting a piece of white plastic (Alex Seymour/Duke University)

Over time, this build-up of blockage could put part of the coral reef in danger.

The researchers conducted two experiments as part of their study.

In the first one, the coral polyps were offered eight different types of microplastics along with clean sand.

They ate all types of plastic but ignored the sand.

The second experiment, the scientists gave the polyps clean microplastics and plastic covered in microbes. Microbes are believed to be a good source of nutrition for marine animals such as corals.

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The researchers found the corals preferred to eat the plastic without the microbes.

They hope their findings will encourage further studies on how taste might play a role in determining why marine organisms eat plastic debris.

Seymour said: “Ultimately, the hope is that if we can manufacture plastic so it unintentionally tastes good to these animals, we might also be able to manufacture it so it intentionally tastes bad.

“That could significantly help reduce the threat these microplastics pose.”

The report is published in the journal Marine Pollution Bulletin.

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