Plastic pollution increases risk of devastating disease in corals

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Coral reefs are sick of plastic.

More than 11 billion plastic objects are polluting Asia-Pacific coral reefs, a new estimate finds. This waste can harbor pathogenic bacteria known to make corals sick. Reefs littered with plastic were at least 20 times as likely to have diseased corals as unpolluted reefs, researchers say. 

Corals succumbing to disease can throw ocean ecosystems out of whack. When corals die, they break down, robbing underwater organisms of their reef habitats. Based on current trends, the amount of plastic trapped in Asia-Pacific reefs is projected to increase 40 percent by 2025, further endangering corals, scientists report in the Jan. 26 Science.

“Plastic has pits and pores. It’s the perfect vessel for microbes to colonize,” says Joleah Lamb, a marine biologist at Cornell University. If these pathogenic microbes get inside coral, they can cause devastating diseases.

The researchers surveyed 159 reefs between 2011 and 2014, documenting diseased coral and plastic debris larger than about the size of a Ping-Pong ball. All of the reefs are located within 50 kilometers of large coastal cities or settlements, from Thailand to Indonesia and south to Australia. The Asia-Pacific region is home to more than half the world’s coral reefs and nearly three-quarters of the world’s human population.

Lamb’s team found that plastic levels varied dramatically by location, with Australian reefs having the lowest levels and Indonesian reefs the highest. That variation was strongly associated with how much plastic waste each country produced, and how the debris was managed, the researchers say.  

The team began its study as part of routine checkups on the reefs, but quickly realized something was wrong. “We didn’t start out looking for plastic and disease,” Lamb says. “But we kept coming across it, so it became necessary to report.”