AUSTRALIA – The Great Barrier Reef, in northeastern Australia, could lose up to a quarter of its reefs over the next 40 years because the corals are losing their ability to tolerate bleaching caused by warming waters,  scientists warned recently.

 “With half a degree Celsius increase in temperature, a quarter of reef corals will lose such protection and 80 percent in a century,” said the Venezuelan Juan Carlos Ortiz, doctor in marine ecology at the University of Queensland.

Ortiz is co-author with Tracy Ainsworth, from James Cook University, in a study published in the journal Science that focuses on the responses of corals to global warming, especially bleaching events, as surface temperature of water rises over a period of 30 years.

This research is reported in amid concerns about the widespread loss of coral reefs in the northern Great Barrier due to bleaching process in which they lose their color as a result of environmental stress, caused in this case by increasing the temperature the sea surface.

The study, which also included experts from the National Oceanic and Atmospheric Administration (NOAA) reveals that corals have responded in the past to bleaching events triggering a metabolic signal that allows them to prepare a few days before the thermal stress produced by marine warming.

Corals usually begin to prepare for a thermal stress when the temperature rises by one degree, which prepares to face rising of two degrees causing these coelenterata laundering.

This protection mechanism reduced coral mortality by 50 percent during bleaching events.

But if the current ocean temperature rises half celsius more, the first peak temperature sends the signal will not be a peak as a signal but will be part of the stress and corals will not have the ability to prepare to respond but will be stressed at once, according to Ortiz.

Ecologist called for taking measures to reduce greenhouse gas emissions because otherwise the reefs will degrade 20 years before the “normal” degradation if the mechanism (protection against thermal stress) is not lost.

According to Ortiz, the Great Barrier Reef will lose all the values for which was declared a World Heritage Site, although the implications affect the whole planet because the current coral bleaching is having devastating effects in places like Hawaii, New Caledonia and next year expected to affect the Caribbean.

“Long-term global reefs are in danger of disappearing as operating ecosystem,” lamented Ortiz.

Corals have a special symbiotic relationship with microscopic algae called zooxanthallae, providing their hosts oxygen and a portion of the organic compounds produced through photosynthesis.

When subjected to environmental stress, many reef corals expel their zooxanthallae mass, and coral polyps are without pigmentation and appear almost transparent on the white skeleton of the animal, ina phenomenon known as bleaching.

The health of the Great Barrier Reef, home to 400 types of coral, 1,500 species of fish and 4,000 species of molluscs, began to deteriorate in the 1990s by the double impact of warming seawater and increased acidity by greater presence of carbon dioxide in the atmosphere.