MARINE researchers monitoring the Solitary Islands Marine Park are studying an expansive outbreak of coral bleaching.
Coral bleaching was discovered on Pocillopora variety corals at South Solitary Island last week.
Coffs Jetty Dive owner Mike Davey has been diving in the area for 20 years and said while there was often some bleaching in summer, the current damage is the most extensive he's seen in more than a decade.
"It's expansive around the island - we've seen it 14 to 18 metres deep as well as in shallower waters where temperatures are higher," he said.
The discovery follows hot, dry conditions associated with the El Nino weather system that has caused mass bleaching events on the Great Barrier Reef.
SCU National Marine Science Centre professor Stephen Smith said high surface temperatures had reached 26.9 degrees at the marine park last week.
"Abnormally high temperatures this year have caused algae in the coral to disassociate from it which has left reefs looking completely white," he said.
"These sorts of corals can handle a temp change but they can't handle extended periods before they start to stress which causes the bleaching."
Mr Smith said bleaching had the potential to impact a variety of marine life dependent on the reef.
"There are so many species that rely on healthy corals and within it lives an amazing invertebrate community. If it dies it impacts a substantial proportion of the biodiversity," he said.
"I regard this as a stark reminder of our duty of care to reduce contributions to greenhouse gas emissions and try and correct this."
Higher temperatures have also attracted a range of tropical varieties to local waters including leopard sharks.
Efforts to document the bleaching are being undertaken by the DPI and Solitary Island Underwater Research Group.
Investigations are also under way at North West Solitary Island and South West Rocks.