Coral bleaching found in Sydney Harbor

Researchers have uncovered coral bleaching for the first time on record in Sydney Harbor, AAP reported on Tuesday.

Recent warm weather in the city is being cited as the likely cause for paled coral colonies found near Sydney Harbor during routine monitoring by PhD candidate Samantha Goyen and Matthew Nitschke from the University of Technology Sydney.

"A warm water influx happened a few weeks ago, which we think was sustained for ... (up to) a week," Nitschke told AAP.

"It appears that week-long period was enough to cause bleaching. "

Coral bleaching occurs when stress such as heat caused the animal to expel the symbiotic algae, loosing vital nutrients and energy reserves, thus color, leading to the wide scale loss of productive habitats for fish.

Nitschke noted that only one of the two main species of coral found in Sydney Harbor seems to be affected by bleaching.

"Corals on upper surfaces, such as on top of boulders, that are exposed to high light levels are the most severely impacted," Nitschke added.

"The conditions have cooled down in the harbor now and that could be enough to make sure they don't all die from this."