By Rich Bowden:

Rising sea temperatures have caused coral bleaching at the world’s southernmost coral reef at Lord Howe Island, say a team of Australian researchers.

Researchers at Australia’s Southern Cross University say warmer than usual seawater temperatures of 25-27 degrees Celsius carried south on the East Australian current over the last few months have led to “…mild to moderate bleaching in some parts of the reef system and almost total coral bleaching in other areas,” according to a March 24 university news release.

Professor Peter Harrison, from the University’s School of Environmental Science and Management, said climate change was having significant impact on the coral reefs of Lord Howe Island.

“This is the southern-most coral reef in the world with a unique mixture of tropical, subtropical and temperate species,” Professor Harrison said. “This is a significant bleaching event, which is likely to lead to some mortality of these corals. This unusual bleaching event is further evidence that climate change is having a very real impact and that even the cooler water, sub-tropical reef systems are not immune to these changes.”

Prof Harrison leads a team of scientists, including Steve Dalton and Andrew Carroll from the National Marine Science Centre, who are studying the damage to the coral reef from rising sea temperatures.

He added that isolation from similar reefs made recovery difficult.

“This coral reef is globally significant but largely isolated from potential source reefs that might serve to replenish populations damaged by severe disturbances, and would take decades to recover from a severe disturbance,” he said.

Lord Howe Island Marine Park manager Ian Kerr was quoted by the university as saying said he was confident the reef would recover

“I’ve seen aerial photographs and I’m pleased to report the beauty and uniqueness of the reef is still intact, we remain very concerned about this event and will continue to facilitate the research and monitoring that needs to continue,” Mr Kerr said.

“We don’t expect a full picture to emerge for a while yet, and possibly not for another year. While there’s no doubt sea surface temperatures contributed to this bleaching, local weather in January was unprecedented. It was the hottest, driest, most cloudless January ever recorded. There was also very little ocean swell which led to poor mixing and thus hotter lagoon temperatures.”

He added conservation measures to protect the reef were already in place.

“Since 2004 no trawling, long-lining or any netting has been allowed in the marine park with nearly 30 per cent of the system protected in sanctuary zones.

“These events show how important marine protected areas are as climate change takes hold and affects the marine environment. The integrity of sanctuaries is very important in the recovery and resilience of these fragile and beautiful reef systems,” Mr Kerr said.

Prof Harrison said he and his team will return in a few months to assess the reef’s recovery.

Tags: climate change, coral bleaching, global warming, Lord Howe Island, marine damage, Southern Cross University