Plastic in oceans killing coral reefs

Coral reefs that come in contact with plastic waste floating in the ocean are at greater risk of becoming diseased, according to an international study published Thursday.

From Australia's Great Barrier Reef to reefs near Indonesia and Thailand, these important underwater ecosystems are being covered with discarded household items, researchers wrote in the study, which was published in the journal Science.

After examining more than 120,000 corals in 159 reefs in the Asia-Pacific, scientists found 11.1 billion plastic items ensnared in them — including diapers, tea bags, shopping bags, fishnets, bottle caps and toothbrushes.

For corals that come in contact with the plastics, their risk of contracting disease rose from 4 percent to 89 percent.

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Plastics don't just hang around populated coastal regions either. Scientists said they were surprised to discover plastic trash in remote reefs as well.

"You could be diving, and you think someone's tapping your shoulder but it's just a bottle knocking against you, or a plastic trash bag stuck on your tank," lead author Joleah Lamb, of Cornell University, told the Reuters news agency. "It's really sad."

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Bacteria-carrying toothbrushes

Although researchers have found a correlation, they're still working on pinpointing precisely how the plastics cause the coral reefs to get sick.

The floating plastic trash could damage the tiny coral animals that build reefs, causing them to become more vulnerable to illness.

"Corals are animals like us and have really thin tissues that can be cut and wounded, especially if they are cut by an item covered in all sorts of micro-organisms," Lamb said.

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Furthermore, bits of plastic can also harbor harmful microbes and bacteria in the oceans, which are then deposited on the corals.

Lamb noted that plastics made of polypropylene — such as toothbrushes and bottle caps — can become "heavily inhabited" by bacteria that are associated with a group of coral diseases known as white syndromes.

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The study also estimated that the billions of plastic items found in Asia-Pacific coral reefs will likely increase by 40 percent in the next few years, meaning that some 15.8 billion plastic items will be found in reefs by 2025.

Coral reefs provide food, coastal protection and tourism income for some 275 million people worldwide who live near reefs. The ecosystems are already under stress from climate change and overfishing.

rs/sms (AFP, Reuters)