Fears flood water runoff could 'smother' Barrier Reef

AFP 15 Feb 19;

Runoff from recent floods in northern Australia is flowing onto parts of the Barrier Reef, scientists said Friday, starving coral of light and providing fodder for the predatory crown-of-thorns starfish.

Parts of northern Queensland are still reeling after nearly two weeks of unprecedented rainfall that turned roads into rivers and inundated hundreds of homes with floodwater.

Scientists at James Cook University say the floods swelled a number of rivers along hundreds of kilometres of coastline, spilling sediment onto the reef which has reduced water quality and much-needed sunlight.

"Coral reef and seagrass need light to maintain their growth and health," researcher Jane Waterhouse from James Cook University told AFP.

Calm weather following the extended period of rain means the murky water is yet to disperse.

It threatens to "smother" coral in areas worst hit, like at the mouth of north Queensland's Burdekin river, where a brown flood plume has spread some 100 kilometres offshore.

"If that were to stay there then eventually, it would not take that long for some of those systems to die off," Waterhouse added.

The effects will not be fully understood until monitoring was completed over the next few of months after sediment has dispersed and settled.

The 2,300-kilometre (1,400-mile) reef has already suffered from back-to-back coral bleaching in 2016 and 2017, where swathes have been killed by rising sea temperatures linked to climate change.

The predatory crown-of-thorns starfish, which eat coral, have also proliferated on the reef due to pollution and agricultural runoff.

The recent floods have exacerbated the runoff, causing algae to grow in some areas.

"This provides a brilliant food source to allow those populations to thrive," Waterhouse added.


Great Barrier Reef coral at risk of bleaching from Queensland flood waters
Marine park authority fear freshwater bleaching after scientists report ‘extensive’ flood plumes and drop in water salinity
Lisa Cox The Guardian 18 Feb 19;

Freshwater bleaching of corals could occur this year as a result of flood waters from Queensland’s overflowing rivers pouring into the Great Barrier Reef, the marine park authority has warned.

The Great Barrier Reef Marine Park Authority told Senate estimates hearings in Canberra on Monday that there is a chance corals hit by mass bleaching in 2016 or 2017 could be damaged again by one of several impacts from the flooding disaster.

Bruce Elliot, the authority’s acting chief executive, said scientists were out monitoring flood plumes on the reef and it was possible that freshwater bleaching could affect inshore reefs.

The discharge of flood waters into the reef could also smother seagrass meadows, which poses a threat to animals such as dugongs and turtles that rely on seagrass as a primary food source.

It has led to deaths of animals after past disasters, such as cyclone Yasi in 2011.

“This event has not been without its ramifications for the Great Barrier Reef,” Elliot said.

“There has been major to moderate flooding of the rivers from the Daintree to the Mackay regions.”

He said it could be weeks or months before authorities had a full picture of the natural disaster’s effect on the marine park.

David Wachenfeld, the authority’s chief scientist, told the hearing there were “extensive” flood plumes on the reef and that unusual wind conditions were carrying them further east and offshore than would normally be expected.

Scientists from James Cook University and the Australian Institute of Marine Science were monitoring the spatial extent of the plumes and their chemical content, he said.

Wachenfeld said scientists had already detected some areas on the reef where the water salinity had dropped to almost half its usual level because of the flooding.

This causes stress for corals and other marine life used to a saline environment, and freshwater bleaching of corals can result.

Wachenfeld said a substantial part of the central Great Barrier Reef was affected by flood waters.

“I’m certainly not able to put any kind of a figure on the spatial extent of the park that’s affected by the flood plumes but I think I can safely say that they are extensive because there are rivers flooding all the way from the Whitsundays in the central Great Barrier Reef, right up to Cape Tribulation in the northern Great Barrier Reef,” Wachenfeld said.

Elliot told the hearing that the recent cooler weather in the region had “markedly” reduced the chance of a mass thermal bleaching this year compared with earlier predictions.

He said forecasts in coming months would be critical in determining the outcome for the reef this season.

In hearings earlier in the day, environment department officials were quizzed on the activities of the environment minister, Melissa Price, who has been questioned for her lack of public appearances during the flooding and other natural disasters this summer, including the record-breaking January heat and the Tasmanian bushfires.

Labor and Greens senators asked officials what public comment the minister had made on the disasters, as well as what meetings she had had with groups including the Wilderness Society, which has said Price failed to respond to correspondence requesting a meeting.

Officials confirmed the Bureau of Meteorology had briefed the minister on the floods but took a question on notice as to whether she had made any public comment on the mass fish kill in Menindee Lakes.

“Surely you can answer that,” Greens senator Sarah Hanson-Young said to the department.

Liberal senator Simon Birmingham said “a minister’s output and their contribution is not measured by their interviews”.