Corals face 'slow starvation' from ingesting plastics pollution, experts find
Corals such as those found on the Great Barrier Reef consume 'microplastics' in the sea at the same rate as their normal food but cannot expel the fragments
Oliver Milman
Tue 24 Feb 2015 21.08 EST Last modified on Wed 14 Feb 2018 12.54 EST
Coastal populations dumped 8m tonnes of plastic rubbish into the oceans in 2010, equivalent to five full shopping bags of debris for every foot of coastline in the nearly 200 countries surveyed. Photograph: Jurgen Freund/Corbis
Corals such as those found on the Great Barrier Reef are at risk from the estimated 5tn pieces of plastic in the world's oceans because researchers have discovered they digest tiny fragments of plastic at a significant rate.
A study led by the ARC centre of excellence for coral reef studies at James Cook University found that corals consumed "microplastics" – plastics measuring under 5mm – about the same rate as their normal food.
These small plastics were found deep within the gut cavity tissue of analysed corals, showing that they weren't able to expel the fragments.
Dr Mia Hoogenboom, who worked on the research, said: "Corals are not very selective in what they eat and they are sensitive to a range of environmental stressors.
"We know in other animals that plastics block feeding activities, as well as soak up toxins. It's quite worrying and it's a reminder that we can manage this kind of stress on the reef at a local level, as well as looking at larger challenges such as climate change."
Researchers took hard corals from different colonies on the central Great Barrier Reef and put them in separate chambers of water, with one chamber of water empty of corals to compare what happened to the plastics.
Plastic fragments weighing 0.4g per litre of water were added, and corals were tested for their reaction over different time periods over the course of a month.
Researchers found that the corals ingested plastics about the same rate of their standard food, such as zooplankton.
Hoogenboom said that while corals benefited from the process of photosynthesis, they also required nutrients from consumed food and would suffer a "very slow process of starvation" should their stomachs become overloaded with plastic.
"In my opinion we need a general focus on cleaning up plastic pollution, to clean up beaches and reduce the amount of plastics in the waterways and into the oceans," she said. "It's a significant problem globally."
Research published in December estimated that there are more than 5tn pieces of plastic, collectively weighing nearly 269,000 tonnes, floating in the world's oceans.
Large pieces of plastic can strangle animals such as seals, while smaller pieces are ingested by fish and then travel up the food chain, all the way to humans.
It is expected this problem will worsen due to the rise of throwaway plastic, such as drinks containers and food packaging, with only 5% of the world's plastic recycled at present.
A separate study published this month found that coastal populations dumped 8m tonnes of plastic rubbish into the oceans in 2010, equivalent to five full shopping bags of debris for every foot of coastline in the nearly 200 countries surveyed.
The coastline of Australia, including the Great Barrier Reef, is not short of plastic pollution, with a 2013 study finding that each square kilometre of Australia's sea-surface water is contaminated by about 4,000 pieces of tiny plastic.
The potential impact of this plastic upon coral raises further concern about the pressures upon the reef, which has suffered a rapid loss of coral cover and may require selectively bred corals to deal with the rapidly warming and acidifying oceans in the future.
The federal government has indicated it is keen on restricting at least one source of plastic, by eliminating the use of non-biodegradable plastic bags.
Greg Hunt, the federal environment minister, said he would be "encouraging" the states to phase out non-biodegradable bags.
"The problem with bags is there are so many of them, and of course they move so easily, just with a little puff of wind they're off and away," Hunt said. "They end up in the gut of fish, they have an impact on our wetlands, they end up in landfill or blowing around, birds can digest them.
"My goal is to get an agreement with the states where each one will move voluntarily to a phase-out. It's a little bit hard under federal law to do that, but you can use the bully pulpit of the national role to make sure that we get rid of these non-biodegradable bags."
A spokeswoman for the Great Barrier Reef marine park authority said that around 683,000 individual items of marine debris, mostly plastic, were collected from beaches in the reef region by volunteers between 2008 and 2014.
"The Australian government has contributed $700,000 from its Reef Trust to clean up marine debris across the Great Barrier Reef," she said.
"As part of the initiative, the existing Eye on the Reef smartphone app will be expanded to help monitor hotspots for marine debris and enable managers to prioritise clean-up areas."