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Coral reefs harmed by eating plastic

http://www.iol.co.za/capetimes/coral-reefs-harmed-by-eating-plastic-1.1823870

Melanie Gosling, Environment Writer

THE scourge of plastic pollution in the ocean has been highlighted by a new study which reveals that corals eat plastic particles as if they were food.

Researchers from Australia’s James Cook University published a paper in the journal Marine Biology which found that corals ate plastic at a rate only slightly lower than their normal rate of feeding on marine plankton.

With global climate change, this is an added stress on coral reefs, ecosystems which contribute enormous financial benefits to humans, especially through fisheries and tourism.

Mia Hoogenboom, head of the university’s centre for coral reef studies, said corals were non-selective feeders. As plastic dumped into the ocean decays, it breaks down into increasingly smaller particles, called microplastics, releasing toxins at the same time.

Hoogenboom said although microplastics were widespread, their impact on marine ecosystems was poorly understood. So researchers set out to see if inshore coral reefs were affected by plastic pollution.

They collected corals from the Great Barrier Reef and put them into seawater contaminated with microplastics. After just two nights, they found the corals had eaten the plastic particles, which were found deep inside the coral polyp, wrapped in digestive tissue. This raised concerns that the plastic may impede the ability of corals to digest their normal food.

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

The project’s next step was to determine the impact eating plastics had on the health and physiology of corals, and whether fish on reefs also ate plastic.

Coral reefs are already being harmed by global climate change, as warming waters have led to coral “bleaching”.

Corals get part of their “food” from algae, which live in their tissues and turn sunlight into food through photosynthesis. The algae and the coral have a symbiotic relationship, and it is these tiny one-celled plants that give corals their colour.

When water temperatures rise, corals become stressed and they expel the algae, so the corals appear bleached. The problem is that corals cannot thrive without these algae.

A study by the World Wide Fund for Nature (WWF) has found that without action to slow global climate change, coral reefs may disappear from the Pacific Ocean’s “coral triangle” by 2100. This in turn will affect the livelihoods of about 100 million people.

The UN Environmental Programme states that although tropical coral reefs cover only 0.1 percent of the ocean, they sustain human society through a range of ecosystem services such as providing livelihoods and food from fisheries, revenue from tourism, erosion prevention and protection from extreme weather events.