Cyclone Jasper and Cyclone Kirrily have crossed the Great Barrier Reef, leaving experts concerned about the vast flood plumes and heavy waves that may have damaged parts of the world’s biggest coral reef system. Reef scientists and conservationists went into the summer worried that an El Niño weather pattern would boost the risk of mass coral bleaching, and now the greatest concerns have come from the cyclones. Freshwater from the rivers can cause corals to bleach, and turbid water can starve reefs and seagrass meadows of light.
Dr. Jane Waterhouse, a water quality scientist at James Cook University’s TropWater research group, says there appears to be “no relief for the reef.” “We’re quite concerned about the potential impacts from the run-off on the reefs in the northern areas,” she said. Marine ecosystems “do not like freshwater,” she said, and some freshwater bleaching has already been observed this summer.
Satellite images reviewed by TropWater in late December showed the discharge from rivers from torrential rains delivered by Cyclone Jasper had extended beyond the reefs closer to shore. Dr. Stephen Lewis, a water quality expert at TropWater, said Cyclone Jasper hit at the end of the sugar cane crushing season, when paddocks had been freshly applied with fertilizers and pesticides. This increased the chances of those nutrients flowing into the reef, but there was little farmers could have done to prevent it.
Cyclone Kirrily AftermathIt is still too early to know the extent of flood plumes from Cyclone Kirrily, but Lewis said monitoring had a major “research gap” because water samples were only taken from inshore reefs. He said water monitoring needed to be extended to better understand how land-based runoff affected reefs farther offshore. Dr. Waterhouse said a new pattern could be emerging under climate change where coral bleaching was interspersed with intense rainfall, giving little time for recovery.
Dr. Roger Beeden, the chief scientist at the Great Barrier Reef Marine Park Authority, said early reports from monitoring suggested the impacts on corals from Cyclone Jasper may not have been as bad as feared. There were only isolated reports of bleaching, he said, but added, “This summer is not over in terms of the pressures that are there.” The federal government will need to hand a progress report to Unesco on its conservation plans for the reef by Thursday, after committing last year to improving water quality and bringing climate targets in line with keeping global heating to 1.5C.
Richard Leck, the head of oceans at WWF Australia, said the flood plumes were a call to action for Queensland and the commonwealth to increase their efforts around catchments, especially on tree clearing. “We still clear about 100,000 hectares around the catchments of the reef every year, and it’s legal. That means the laws are not fit for purpose,” he said. Leck said the Queensland government would be able to report new state climate targets, announced in December, to cut emissions by 75% by 2035 based on 2005 levels.