Sediment runoff is not only a direct threat to the Great Barrier Reef, but is affecting how coral recovers from other threats, new international research has found.
A joint study by the Canadian Dalhousie University along with James Cook University’s ARC Centre of Excellence for Coral Reef Studies and the University of Adelaide analysed 20 years of satellite footage of the southern end of the reef.
The study’s co-author, JCU PhD candidate Sam Matthews, said they found the coral in areas affected by regular runoff recovered more slowly than the coral in more pristine areas.
“Improving water quality is something that’s going to do a lot of good for the Great Barrier Reef,” Mr Matthews said.
“Our results provide strong support for government policies aimed at reducing nutrient pollution to help increase the resilience of the Great Barrier Reef, in recovering from damage due to tropical cyclones, crown-of-thorns outbreaks and coral bleaching.”
Mr Matthews was quick to point out there was “no silver bullet” for improving the overall health of the reef, but improving overall water quality was a major factor in assisting recovery.
Most recently the reef has been hit with a massive runoff plume thanks to the north Queensland floods, however the ordinary contributor to sediment runoff is largely farming.
The Queensland government has released a framework setting targets for sediment runoff levels into the reef.
Last month the government introduced laws to enforce the 2050 targets, which are set to be debated later this year.
The study found that an improvement of between 6 and 17 per cent in water quality may buffer the predicted increases in coral bleaching at some inshore locations.
That level of improvement is within the scope of the government’s improvement plans, but the Australian Marine Conservation Society Great Barrier Reef campaign manager Lissa Schindler said the targets are unlikely to be met.
“There is concern that they’re running out of time to meet those targets, because the first set of deadlines in 2025 and it’s 2019 now,” Dr Schindler said.
“So we really need the government to rapidly put these laws through parliament and then enforce them.”
Water sediment affected reefs closer to the shore more than those further out, the study found.
Aside from environmental concerns, that was alarming because the inner reefs are more commonly used for income-generating tourism activities.
In a small silver lining the research found areas of the reef affected by sediment runoff were partially protected from the effects of coral bleaching.
However, lead author Aaron MacNeil of Dalhousie University said that was offset by the sediment-affected areas being more susceptible to disease and outbreaks of crown-of-thorns starfish.
“Perhaps most critically, poor water quality reduced the rates at which coral cover recovers after disturbances by up to 25 percent,” Dr MacNeil said.
“This shows that, by improving water quality, the rates of reef recovery can be enhanced.”