Sarah Clarke, ABC News 24 Mar 10;
Updated March 24, 2010 10:27:00
Parts of the world's most southerly coral reef are under threat after it suffered its largest-recorded bleaching event.
Lord Howe Island is well known for its pristine environment and natural beauty.
The island's isolation has allowed it to develop unique and endemic marine life and the waters contain an unusual mix of tropical, sub-tropical and temperate corals.
But since January the waters around Lord Howe have experienced unusually warmer temperatures. The average rose by two degrees Celsius and the corals are showing the first signs of extensive bleaching.
And unlike the Great Barrier Reef, where corals have been known to recover, the genetically unique reef at Lord Howe could take decades to regenerate.
Peter Harrison from the Southern Cross University says it is the most significant bleaching event ever recorded at Lord Howe Island.
"The significance of this is that Lord Howe Island has the southern-most coral reef, so when that starts to see signs of extensive coral bleaching we know that the climate is definitely changing," he said.
Professor Harrison and a team of scientists have spent the past week diving off Lord Howe Island, assessing the extent of the stress.
In 1998, the reef survived relatively unscathed despite widespread coral bleaching around the world.
This year, not only have the ocean temperatures been higher, but conditions have been unusually calm.
And that has contributed to the significance of the bleaching.
The island's marine park manager, Ian Kerr, says the still conditions meant water was not flushed out of the lagoon.
"So the lagoon especially had higher temperatures than it normally does and higher UV light," he said.
It is not known how much of the reef will recover.
Professor Harrison says some mortality is expected but cooler temperatures over coming months may reduce the stress.
"At the moment we really can't determine whether or not there [will] be serious mortality of corals at some of these sites or not," he said.
"It was personally very upsetting to go back to this absolutely gorgeous reef environment.
"It should be noted that at the moment it is still a beautiful pristine reef environment, but to go back and see so many of these corals bleached was really upsetting to me personally.
"I am hoping that the cooler sea temperatures will allow a decrease in stress and most of these corals come back really quickly and recover fully.
"But at the moment it is on a knife edge."
Coral reef on Lord Howe bleached by summer
Bridie Smith, Sydney Morning Herald 25 Mar 10;
THE world's southernmost coral reef is on a knife edge, according to scientists who say this summer's above-average water temperatures have left Lord Howe Island's unique reef stressed and bleached.
In parts of the reef, especially areas around the island's lagoon, up to 95 per cent of corals have been bleached since January.
''This is a significant bleaching event,'' said Peter Harrison, director of marine studies at Southern Cross University, who has been monitoring the reef since 1993.
Professor Harrison said the situation, caused by warmer-than-usual waters carried south by the currents from the Great Barrier Reef, had been compounded by a period of light winds and little cloud cover.
''That means both increased temperature and increased light penetration into the water, which stressed the symbiotic algae which lives in the corals,'' he said.
It is the first major bleaching of the reef, which is considered globally significant because of its unique combination of tropical, subtropical and temperate species.
Professor Harrison said the bleaching was significant for another reason. This, he said, was evidence that subtropical areas were not immune to the impact of climate change.
''It is a clear warning that changes to climate will impact not only the tropical coral systems but also the subtropical ones,'' he said.
Professor Harrison said there was no guarantee that all damaged corals would recover.
While he stressed that not all the island's 100 coral species had been bleached, he said the recovery of damaged corals could take many months.
Unlike the Great Barrier Reef, the Lord Howe Island corals are geographically and genetically isolated, which makes recovery a much longer process.
''At the moment the corals are really on a knife edge,'' he said. ''Many of the corals are very badly stressed. We're hoping that most will recover, but at the moment we can't tell. So we're going to have to go back in a couple of months to repeat the surveys.''
He said the effect of the water temperature exceeding 26-27 degrees in the past few months had been significant for the crescent-shaped island, which is a World Heritage site in the Tasman Sea, 600 kilometres east of the NSW.
In 1998 Professor Harrison said the maximum temperature recorded in the island's lagoon was just over 27 degrees. This year it passed 28 degrees, more than two degrees above normal summer water temperatures.
Monthly temperatures are just as revealing. Last March the sea water temperature was 22 degrees, compared with 26 recorded this month.
''The stress largely happened when it peaked at 28 degrees in February,'' he said. ''It only takes a few weeks of above-normal sea temperatures to make the difference for these corals.''
Climate change puts Australian reef on 'knife edge'
Yahoo News 24 Mar 10;
SYDNEY (AFP) – The world's southernmost coral reef is on a "knife-edge" after warmer seas blamed on climate change bleached large parts of it for the first time, an Australian scientist warned on Wednesday.
Peter Harrison, who has been monitoring the world heritage-listed Lord Howe Island since 1993, said a two degrees Celsius (four Fahrenheit) rise in sea temperatures had drained much of the reef of its distinctive colours.
"We're hoping the vast majority of these corals will be able to recover, but at the moment this whole system is on a knife-edge and we don't know what's going to happen," Harrison told AFP.
Harrison, whose Southern Cross University team surveyed the reef about 600 kilometres (370 miles) east of Sydney this month, said the unusually warm water had travelled down from tropical seas around Australia's Great Barrier Reef.
He blamed the warmer seas on climate change and said the reef could face "an even more severe event" in the future.
"It's exactly what you predict from warming seas," Harrison said. "This is a warning of likely future increases of stress on this world's southernmost reef."
Harrison said the reef will survive if the seas return to their normal temperatures quickly enough, but could take decades to recover from a severe bleaching.
He added that the damage was also affecting other marine life, including a type of anemone which provides a home for a rare type of fish.
Bleaching occurs when overheated corals expel crucial algae that give them their colour.
Warm waters bleach corals
Southern Cross University, Science Alert 26 Mar 10;
Above average sea temperatures throughout the early part of 2010 have led to the first recorded major coral bleaching event at Lord Howe Island, the world’s southern-most coral reef.
Water temperatures have exceeded 26-27 degrees over the last few months, which is a couple of degrees warmer than the usual summer sea temperature, leading to mild to moderate bleaching in some parts of the reef system and almost total coral bleaching in other areas.
The reef lies within the Lord Howe Island Marine Park and is part of the Lord Howe Island World Heritage site.
Southern Cross University researchers have mapped the extent of the bleaching and damage to the corals at the request of the Marine Parks Authority and will return to assess the rate of recovery.
Professor Peter Harrison, from the University’s School of Environmental Science and Management, has been monitoring the coral reefs off Lord Howe Island since 1993. He is leading a team of researchers including Steve Dalton and Andrew Carroll from the National Marine Science Centre.
"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."
Professor Harrison said the danger for these reefs was that, unlike the Great Barrier Reef, they were geographically and genetically isolated making recovery a much longer process.
"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.
Professor Harrison said two of the major sites affected by the bleaching were within sanctuary zones within the marine park, and noted that research from other tropical reefs showed that areas protected from fishing had better recovery rates from severe coral bleaching episodes.
This recent bleaching event, caused by warm seawater carried south on the East Australian Current, is much larger than the minor coral bleaching event that took place at Lord Howe Island in 1998. The 1998 mass coral bleaching event severely damaged many coral reefs around the world, whereas at Lord Howe Island relatively new coral species became bleached and most corals recovered after the 1998 bleaching period.
Lord Howe Island Marine Park manager Ian Kerr said while some mortality was expected he was hopeful of a good recovery with many of the most severely affected sites within sanctuary zones in the marine park. He said the Marine Parks Authority would continue to do everything to monitor and assess the situation.
"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.
"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.
Professor Harrison said his team planned to return to Lord Howe in a few months to complete further surveys and assess the extent of coral and reef community recovery.
