Study: Coal Spill Risk to Australia's Great Barrier Reef

Any major coal spill on Australia's Great Barrier Reef could kill some colorful corals within two weeks and stunt the growth of fish and seagrass, a new study revealed Tuesday.

While coal spills are rare, environmentalists have been increasingly concerned about the risks to the reef from ships carrying the commodity mined in Queensland state through its waters.

The study, published in Nature Scientific Reports, is the first to examine the effect of fine coal particles on tropical marine organisms.

"Results demonstrate that chronic coal exposure can cause considerable lethal effects on corals, and reductions in seagrass and fish growth rates," it said.

In experiments in which marine species were exposed to varying levels of fine coal particles, the researchers found that it had a "smothering" impact on corals, co-author Mia Hoogenboom told Agence France Presse.

Hoogenboom, from Australia's Centre of Excellence for Coral Reef Studies, said there was a stickiness to coal dust which formed a film on coral which light struggled to penetrate.

"From our study it was the coral that was the most vulnerable, where we saw extensive mortality of the coral tissue," she said.

"For the sea grass and the fish we saw lower levels of mortality but we did see significant impacts on their growth rates."

Kathryn Berry, who led the experimental research, said corals exposed to the highest concentrations of coal dust died within two weeks.

"Corals exposed to lower concentrations of coal lasted longer, but most of them also died after four weeks of exposure," she said in a statement.

Berry said while some fish and seagrass died from coal dust exposure, it was more likely to stunt their growth by half compared to how they would have grown in clean water.

The reef is suffering its worst bleaching in recorded history with 93 percent of corals affected due to warming sea temperatures. Any coal spill would add to problems caused by farming run-off, development and the coral-eating crown-of-thorns starfish.

A catastrophe was averted when the Chinese-registered coal carrier Shen Neng 1 foundered in the marine park in 2010. But the huge ship gouged a three kilometre-long (1.8 mile) scar in the reef and was stranded for nine days before salvagers could refloat it.

Queensland state Environment Minister Steven Miles moved to reassure people, saying the reef was "the most strictly regulated shipping area in the world".

The transit of coal through the World Heritage-listed marine park was not, he stressed, the biggest threat to the reef.

"The main localised threats are sediment and nutrient run-off from the land and the big long-term threat is climate change," he said in comments cited by the Australian Broadcasting Corporation.

"Shipping is something we need to very closely regulate but we shouldn't let us distract us from what the main threats are."