VIDEO: Coral in Sydney Harbour has been hit by bleaching

Divers taking samples of coral bleaching in Sydney Harbour. Image: UTS

Coral in Sydney Harbour has started to bleach just like the Great Barrier Reef.

Scientists say the process, often triggered by unusually warm summer and consequently warmer waters, took just a few weeks.

“Although these corals are specialists in cooler waters, what we didn’t expect was to see such a rapid change in their physiology,” says Samantha Goyen, a PhD candidate at the University of Technology in Sydney.

“In comparison to those of the Great Barrier Reef these coral populations are little studied. Scientifically there is still so much we don’t know about these corals considered to be living in an already extreme environment.”

Goyen and Dr Matthew Nitschke from the UTS Climate Change Cluster discovered the paled coral colonies during routine monitoring at a number of locations.

Joshua Madin at Macquarie University has been monitoring these corals since 2010 as part of a project aimed at understanding the migration of tropical corals down the NSW coastline.

“To our knowledge, bleaching like this has never been observed in Sydney Harbour corals,” says associate professor Madin.

“Where we normally see corals here with vibrant hues ranging from iridescent green to a reddish-bronze, many of them are now showing clear signs of bleaching.”

Bleaching occurs when the coral experiences physiological stress for extended periods.

Sea-surface temperatures rising above normal for the season are widely recognised as a major contributing factor to bleaching.

In Sydney Harbour, the scientists are optimistic the corals can recover as conditions return to normal.