11 billion bits of plastic killing reefs: Study

More than 11 billion items of plastic are lodged in corals across the globe, say scientists.

Plastics in the oceans are killing corals by increasing their risk of becoming diseased, scientists have shown for the first time.

Researchers have calculated that there are now more than 11 billion items of plastic lodged in corals across the globe, raising the risk of deadly infections by up to 89 per cent. Corals are already under attack from ocean acidification and warming seas, which is causing mass bleaching.

But for the first time, scientists have shown the impact of plastic. They believe the rubbish attracts micro-organisms which can carry disease.

The team from James Cook University, Cornell University and the US National Oceanic and Atmospheric Administration, surveyed more than 120,000 corals on reefs from Indonesia, Australia, Burma and Thailand.

Dr Joleah Lamb, from the ARC Centre of Excellence for Coral Reef Studies based at James Cook University, said: "We don't know the exact mechanisms, but plastics make ideal vessels for colonising microscopic organisms that could trigger disease if they come into contact with corals. For example, plastic items such as those commonly made of polypropylene, like bottle caps and toothbrushes, have been shown to become heavily inhabited by bacteria ... associated with a globally devastating group of coral diseases known as white syndromes."

Researchers fear the problem is getting worse. They estimate that plastic on reefs will increase by 40 per cent in the next seven years, with 15.7 billion items choking corals by 2025.

Plastic was found to trigger skeletal eroding band disease, white syndromes, and black band disease.

Professor Bette Willis said: "Bleaching events are projected to increase in frequency and severity as ocean temperatures rise. There's more than 275 million people relying upon coral reefs for food, coastal protection, tourism income, and cultural significance. So moderating disease outbreak risks in the ocean will be vital for improving both human and ecosystem health."

Each year 10 per cent of the more than 270 million tonnes of plastic produced globally will end up in the sea.

A recent study, meanwhile, estimated that nine in 10 of the world's seabirds have plastic in their guts. Chemicals from plastic also leach into the water, and it has been shown that even humans who eat seafood ingest 11,000 pieces of microplastic each year.

The research was published in the journal Science.