Coral feed in a number of ways. They receive energy from photosynthesis from symbiotic algae living within the coral. They also feed on ocean sediment, plankton and microscopic organisms. Recently a team of Austrian researchers found that, when it’s available, the coral of the Great Barrier Reef will also feed on micro-plastic pollution.

“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,“ says Dr Mia Hoogenboom in a statement.

Hoogenboom is a Chief Investigator with the ARC Centre of Excellence for Coral Reef Studies at James Cook University.

According to another recent study, the amount of plastic in the Ocean is incredible. The research, led by co-authored by Kara Lavender Law, principal investigator of the NCEAS marine debris working group, suggests that between 4.8 and 12.7 million metric tons of plastic are entering the ocean annually.

That research, published in the February 13 edition of the journal Science, additionally found that only a very small percentage of that total amount is being found on the ocean’s surface. The number provided was 6,350 and 245,000 metric tons out of millions.

Micro plastics come from a variety of sources. Primary micro plastics start out as very small particles, they are frequently used in medicines and as scrubbers in cosmetics and cleansers.

The secondary source of micro plastics comes from the breakdown of larger plastic debris. While plastic may not biodegrade it can be broken down into very small particles. This can happen to plastic waste dumped into the ocean but it can also happen with plastics on land, including in landfills, and then find its way into open water.

Despite the rapid proliferation of micro plastics in the ocean, their impact on organisms and ecosystems is only beginning to be understood.

“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,” said Dr Hoogenboom.

For the purposes of the study, the researchers collected coral from the Great Barrier Reef and placed them in water contaminated with micro-plastics. After 48 hours the team found that the coral had eaten some of the plastic.

“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,” said study lead author Nora Hall, a James Cook University Masters graduate.

Further examinations revealed that the consumed plastic was found wrapped in digestive tissue inside the corral polyp. This raised concerns about the potential impact on the corals digestive abilities.

Additionally, the team tested the waters adjacent to the Great Barrier Reef for traces of plastic.

“During this testing we found microplastics, including polystyrene and polyethylene, although only in small amounts,” says study co-author, Kathryn Berry, a PhD student at James Cook University and the Australian Institute of Marine Science.

The team next plans to conduct further studies on the impact on the health of the coral and other inhabitants of the reef.

“We are also investigating whether fish on coral reefs eat plastics, and whether plastic consumption influences fish growth and survival.” Dr Hoogenboom says.
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The researchers work can be found in the journal Marine Biology.