There are fears for the future of the marine organisms which form ecosystems such as the Great Barrier Reef in Australia.
While seagulls, turtles and fish may mistake plastic for prey, a study suggests corals deliberately eat it instead of nutritious alternatives because it tastes good to them.
The findings, by Duke University in North Carolina, raise concerns because plastic poses a risk of choking or intestinal blockages that could kill off areas of coral reef.
The study’s lead author, Austin Allen, said: “Corals in our experiments ate all types of plastics but preferred unfouled microplastics … over microplastics covered in bacteria. This suggests the plastic itself contains something that makes it tasty.”
Threats to corals include “bleaching”, which turns it white as a result of unusually warm ocean temperatures, overfishing and pollution including plastic waste.
The US researchers looked at microplastics measuring up top one fifth of an inch.
In the first experiment, corals collected from the coast of North Carolina were offered eight different types of plastics and similarly-sized items such as clean sand.
They ate every type of plastic but mainly ignored the sand.
The second experiment saw the corals offered clean plastic fragments, or plastic covered in microbes which they are believed find tasty and nutritious.