Polluted Outflow From Only Two Flooding Australian Rivers Already Covering 11% Of Great Barrier Reef

[hatrack]

The floods that have devastated swathes of southern Queensland are beginning to perturb one of the world's largest World Heritage Sites, the Great Barrier Reef, scientists in Australia say. Southern parts of the reef, which extends more than 2,000 kilometres along the Queensland coast in northeastern Australia, are already being affected by the huge plume of polluted water that is gushing from many Queensland rivers. The full impact of the floods will take several years to play out, and they could eventually affect the entire reef system.

"The amount of water entering the reef, with rivers along southern Queensland all in flood — we haven't seen that before," says Michelle Devlin, a water-quality researcher from James Cook University in Townsville, Queensland, who is leading efforts to monitor the flood plume. Outflows from two catchments alone, the Burnett Mary and the Fitzroy River regions of central Queensland, already cover 11% of the ocean surface of the Great Barrier Reef, Devlin and her colleagues have found. And corals there are at risk of the direct, acute effects of the polluted floodwater.

The immediate impact of the floodwater is simply vast amounts of fresh water running into the sea. Fresh water kills coral, so shallow inshore reefs in the path of the plume are threatened. As the pulse of cloudy, nutrient-rich, pesticide-polluted water spreads, it also smothers coral in deeper waters, blocking out light and limiting photosynthesis while boosting the growth of coral competitors such as macroalgae.

Devlin is now mapping the spread of the floodwater through the southern Great Barrier Reef. Satellite images show that the prevailing southeasterly winds have so far confined the plume to within about 65 kilometres of the shore. These winds are forecast to drop later this week, which could see the plume spread much farther out into the reef.

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http://www.nature.com/news/2011/110118/full/news.2011.21.html