Researchers surveying beaches in Japan's Ryukyu Islands have identified a new form of marine pollution: plastic that has melted and fused directly into coral skeletons. The scientists, who collected samples from three beaches on Okinawa, used spectroscopic analysis and micro-CT scans to confirm that polymers from common household plastics had seeped into the microscopic pores of coral rubble. They have named the resulting material "plasticoral."
This is the first time plastic has been seen fused with corals, though similar phenomena have been observed elsewhere. In 2019, researchers found degraded plastic coating mussels and algae in tide pools, a material they called "plastiskin." The exact mechanism behind the coral fusion is not yet confirmed, but the researchers consider beach bonfires the leading candidate, since ocean temperatures are not high enough to melt plastic on their own.
Coral rubble, even after washing ashore, often returns to sea and provides a stable foundation for new corals and habitat for small marine organisms. How plasticoral might affect these ecosystems is unknown, but previous research has shown that chemicals leaching from plastics can inhibit coral reproduction and that plastic fragments can carry pathogens to corals. Given the pervasiveness of plastic pollution, the authors suggest that fires on even seemingly pristine beaches could be creating these unintended fusions.