GREAT BARRIER REEF MAY EXPAND

Researchers have found remarkable levels of recovery on the Keppel outcrops devastated by bleaching in 2006.

The research goes against the scientific consensus that much of the reef would die unless greenhouse emissions are checked and that bleaching would wipe out much of the fragile coral if climate change continued to warm surface temperatures.

Scientists who predicted corals would be mostly extinct by mid-century had a credibility problem because the Great Barrier Reef was in "bloody brilliant shape".

The famous reef had defied predictions that it would be overwhelmed by crown of thorns starfish, smothered in sediment from river runoff or poisoned by sediment and chemicals washed on to corals from the mainland.

Ocean acidification associated with climate change remains a genuine danger, however, because it could impede the process of coral calcification, destroying the reef's building block.

Leading scientists including former AIMS chief scientist Charlie Veron and reef research pioneer Ove Hoegh-Gulberg, who attended the Copenhagen talks on climate change, have warned that the Great Barrier Reef will be destroyed by the middle of the century if ocean temperatures continue to rise, unleashing more frequent and lethal bleaching.

Mass bleaching was recorded on the Great Barrier Reef in 1998 and 2002, affecting up to 60 per cent of all corals. The last severe outbreak, in which stressed corals eject the symbiotic algae that provide them with nutrients, causing many to die, was localized on the Keppel reefs three years ago.

More than 95 per cent of the corals were affected, of which about a third died. The corals became stressed after the water temperature topped 28.5C and began to die when it hit 30C and stayed at that level for a week or more, with limited wind or cloud cover to ease the heating.

Scientists have found the tolerance level of corals varies. Reefs around Magnetic Island, off Townsville, can withstand water temperatures in the low 30s, while those off Yemen, at the foot of the Arabian Peninsula, live in temperatures that can reach 34C.

Some of the corals on the Keppel outcrops are more thickly covered in coral than before bleaching in 2006, raising hope the living heart of the reef can acclimatize to spikes in water temperature apparently through a process known as algal shuffling.

Some scientists claim that the latest findings are more optimistic about the ability of corals to adapt to climate change, especially on inshore reefs such as those in the Keppels.
The Great Barrier Reef is 2000km long, with 3000 reefs. Some of the coral areas are more naturally resilient than others.