BY KATIE - MYGREENPOD, 24 Feb'15

RESEARCH FINDS CORALS AROUND AUSTRALIA’S BARRIER REEF EAT PLASTIC

Researchers have found that corals commonly found on the Great Barrier Reef will eat microplastic pollution at a similar speed to their normal rate of feeding on marine plankton.

Microplastics, including polystyrene and polyethylene, were present in low concentrations at all the researchers’ sampling locations adjacent to inshore reefs on Australia’s Great Barrier Reef.

Message from the Gyre – by Chris Jordan, Seattle

’Non-selective feeders’

Microplastics, which measure less than 5mm in diameter, are tiny fragments of plastic in the environment. They’re a widespread contaminant in marine ecosystems, particularly in inshore coral reefs.

During experimental feeding trials, the researchers found that corals mistake microplastics for prey.

‘Corals are non-selective feeders and our results show that they can consume microplastics when the plastics are present in seawater.

‘If microplastic pollution increases on the Great Barrier Reef, corals could be negatively affected as their tiny stomach cavities become full of indigestible plastic.’

Dr Mia Hoogenboom, a chief investigator with the ARC Centre of Excellence for Coral Reef Studies at James Cook University

Unknown impacts

The impact of plastic products accumulating in the environment is poorly understood, but the researchers suggest that, as microplastics act as both a sink and a source of environmental contamination, they can be considered a harmful pollutant.

Plastics adsorb and transport other contaminants in seawater, such as heavy metals and organic pollutants. Like the plastics, these contaminants don’t easily degrade in the environment or during digestion by organisms, meaning they can bioaccumulate in the food chain.

‘Marine plastic pollution is a global problem and microplastics can have negative effects on the health of marine organisms.

‘We aimed to determine whether corals from inshore coral reefs consume microplastics, and whether there is potential for plastic pollution to affect coral reefs.’

Dr Mia Hoogenboom

Digesting plastic

As part of the study, the researchers put corals collected from the Great Barrier Reef into water contaminated with plastic. After two nights they found that the corals had eaten plastic particles.

‘Corals get energy from photosynthesis by symbiotic algae living within their tissues, but they also feed on a variety of other food including zooplankton, sediment and other microscopic organisms that live in seawater.

‘We found that the corals ate plastic at rates only slightly lower than their normal rate of feeding on marine plankton.’

Nora Hall, study lead author and Masters graduate from James Cook University

The plastic was found deep inside the coral polyp wrapped in digestive tissue, raising concerns that it might impede the coral’s ability to digest its normal food.

Plastic in our oceans

The researchers say the next step is to determine the impact plastic has on coral physiology and health, as well as its impact on other marine organisms.

‘We are also investigating whether fish on coral reefs eat plastics, and whether plastic consumption influences fish growth and survival’, said Dr Hoogenboom.

The United Nations Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP) has estimated that land-based sources are responsible for up to 80% of marine debris, with the remainder caused by sea-based activities.

Studies have shown that plastics consistently make up 60-80% of all marine debris. In the fishing industry, plastic materials and synthetics have replaced natural fibres over the past 35 years and their widespread use has resulted in substantial amounts of derelict fishing debris in ocean waters and on beaches.

Once it reaches the ocean, about half of plastic debris floats and can therefore travel on currents for thousands of miles.

Microplastic ingestion by scleractinian corals, by N.M. Hall, K.L.E. Berry, L. Rintoul, M.O. Hoogenboom, can be read here.