Oceanic plastic pollution is helping to spread colonising microbes to coral reefs from Thailand to Australia's Great Barrier Reef, greatly increasing the risk of a group of coral disease known as white syndromes, according to a new study published in the journal Science.
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The findings come after scientists discovered last year that marine animals washed out to sea during the Japanese tsunami in 2011 had been surviving for up to seven years at sea on plastic rafts before washing up on the US coast. 

According to the study, in the Asia-Pacific region a total of 11.1 billion plastic items - including shopping bags, fishing nets, even diapers and teabags - are entangled on reefs.

They projected the numbers would rise by 40% by 2025 as marine pollution gets steadily worse. Where plastic had come into contact with coral, the likelihood of the presence of disease rose from 4% to 89%, which is a 20-fold increase.

The study's author Dr Joleah Lamb said ‘plastic flotsam' is known to be used as stable vessels for algae and other organisms, including some that may carry coral-killing pathogens. 

"There's a disease called black-band disease - it's a thick black band that can move across the coral and cause tissue damage," Lamb told the ABC.

"It's made up of a consortia of different types of organisms, and they really like a low-oxygen, low-light environment.

"So the plastic sitting on top of the coral can cause these micro-climates that are really wonderful for these types of bacteria to proliferate.

"With more than 275 million people relying on coral reefs for food, coastal protection, tourism income, and cultural importance moderating disease outbreak risks in the ocean will be vital for improving both human and ecosystem health."

The team of researchers ran a series of 20m transects, examining each piece of coral that fell along each transect line. They positively identified the presence of six different types of coral diseases.

Researchers examined nearly 125,000 reef-building corals on 159 coral reef systems from Australia, Indonesia, Myanmar and Thailand. They found Indonesian reefs typically contained around 25 items of plastic per 100sqm compared to 0.4 items over the same area on reefs in Australia.

The researchers estimate based on current trends there will be more than 15 billion items of plastic on coral reefs by 2020. Out of the top 10 worst plastic polluters in the world, nine are in the Asia-Pacific, with researchers blaming poor waste management for much of the plastics that enter the ocean. 

In response, the federal government earlier this month announced a $60 million plan to protect the famous maze of coral, including funds to combat the crown-of-thorns starfish, coral bleaching and examine ways to prevent polluted water from hitting the reef. 

Separately, the Queensland government has earmarked $256 million over the next five years to improve reef water quality.

Moving forward, the researchers urged for tougher restrictions on plastic waste. In December, almost 200 nations agreed to limit plastic pollution of the oceans, warning that it could outweigh all fish by 2030.