The full impact of the floods, which are rushing huge volumes of water into the pristine surrounds of the world's largest coral reef, is not yet known, but the influx will stress the colourful corals, said Michelle Devlin.
"This does impact on the reef. It just impacts on the reef's resilience so you get very stressed corals, you get stressed sea grass," Devlin, a researcher at James Cook University in northern Queensland, told AFP. "So let's just say that a big cyclone came along, knocked them all out. They might not recover so well because they are already very stressed."
Devlin said while the rivers have always poured into the reef, the floods were no longer bringing just rainwater but also sediment, nutrients and pesticides. "Top soil will run straight off into the water and that will come straight out into the Great Barrier Reef," said the researcher, who chased the flood plumes by boat to take samples and track the extent of the damage.
"There's a lot of water around and already it would be influencing the reef," she said, describing the mixture of fresh, warm water, nutrient-heavy soil and pesticide run-offs as a harmful "cocktail" for the corals. "There is just going to be this cocktail of water containing a lot of things that they (the corals) wouldn't necessarily have seen before. It is fresh, warm water and that will stress corals out as well."
Devlin said flood plumes were visible near the coastal city of Rockhampton, where floods have virtually cut off the town of 75,000, and already stretched to up to 40 kilometres offshore. As more floodwaters brought by weeks of torrential rains make their way to the coast, the dirty river water will pour into the reef for weeks, enabling the plume to extend for hundreds of kilometres, she said.