“So if corals are exposed to this for significant periods, they’re really going to suffer badly.”
The research, published in the journal BMC Genomics on Friday, used the genome of the common reef-building coral, Acropora millepora, to detect changes in the coral’s biology.
During the recent flooding in north Queensland, a massive flood plume was detected pushing out from the Townsville region, with estimates nearshore reefs were exposed to roughly half the normal ocean salinity.
The report’s co-author, Dr Jean-Baptiste Raina from the University of Technology Sydney, said that part of the reef was heavily affected in the 2017 bleaching event, and was only in the early stages of recovery.
“The fact that it follows several years of very high temperatures means those corals aren’t getting any rest,” Dr Raina said.
“So when it’s not high temperature it’s rain, and it seems the stresses are never-ending at the moment and are not letting the reef recover.”
In a grim irony, scientists had been hopeful that part of the reef could start recovering more fully this year because the frequent rain in north Queensland had kept overall ocean temperatures down.
The researchers said with more extreme weather events predicted in the coming years, more needed to be done to protect the reef from runoff.
They admit Acropora millepora coral is particularly sensitive to changes in salinity, but add that most other corals are also susceptible to a greater or lesser degree to rapid desalinification.
“This is kind of an underappreciated phenomenon,” Professor Miller said.
“There’s a wider appreciation of the fact that extreme temperature events cause damage to reefs, it’s less well-known that low salt conditions caused by extreme rainfall are similarly damaging to coral reefs.”
It’s estimated the Great Barrier Reef contributes about $6.4 billion a year to the Australian economy, mostly through tourism and the reef’s status as an international icon.
Stuart Layt covers health, science and technology for the Brisbane Times. He was formerly the Queensland political reporter for AAP.