By Oliver Milman
24 February 2015
(The Guardian) – Corals such as those found on the Great Barrier Reef are at risk from the estimated 5 trillion 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. [more]