Great Barrier Reef suffers 'tragic' coral bleaching event

This is utter rubbish.  Bleaching events are poorly understood but one thing we know is that they are NOT a response to warmer water.  Corals are at their most prolific in Torres strait, the part of Australia nearest to the equator, and hence the warmest East coast waters.  And in any case even NOAA's "adjusted" figures showed only 13 hundredths of one degree global  temperature rise in 2015

Fears of a mass coral bleaching event on the Great Barrier Reef have prompted federal authorities to issue an urgent warning on the natural wonder, which is *under threat from climate change*.
The Great Barrier Reef Marine Park Authority on Tuesday said patchy bleaching had been detected on multiple reefs in mainly shallow areas, and weather forecasts of upcoming hot conditions posed a dangerous threat over the next few weeks.

In a statement, the authority said the conditions had triggered "level one incident response" involving more in-water field surveys and monitoring by authorities and researchers.

Climate action advocacy group 350.org said the bleaching was "tragic" and the Turnbull government should block what would be Australia's largest coal mine, by Indian mining giant Adani, and commit to halting new fossil fuel projects nationally.

The authority said the bleaching had occurred in mainly shallow areas where corals are often exposed to high levels of sunlight.
Chairman Russell Reichelt said February and March were the highest risk periods for mass coral bleaching on the reef because of hot, dry El Nino conditions and high sea surface temperatures, adding "the next few weeks will be critical".

"Bleaching is a clear signal that living corals are under physiological stress. If that stress is bad enough for long enough, the corals can die. Corals generally have a temperature limit, and the bleaching indicates they're outside of their comfort zone," Dr Reichelt said.

"At this stage, there appears to be low rates of coral mortality restricted to a small number of reefs, and most of the corals affected by bleaching are those that are particularly vulnerable to this type of event such as plate and branching corals."

The authority says the most common cause of coral bleaching is sustained heat stress, which is occurring more frequently as the climate changes.

Dr Reichelt said the Bureau of Meteorology and the United States' National Oceanic and Atmospheric Administration had forecast a high probability of heat stress that would cause further bleaching.

While sea surface temperatures were fluctuating across the 345,000 square kilometre marine park, in some areas they had reached 2.5 degrees above the summer average, which was exacerbated by lack of cloud cover, he said.

"What happens now will be entirely dependent on local weather conditions. If we're fortunate enough to receive plenty of cloud cover, which will effectively provide shade, it will go a long way to reducing heat absorption by the ocean and alleviating thermal stress on corals," he said.

Dr Reichelt said the bleaching event was less severe than that which has occurred across the Pacific during the current global bleaching event. The authority says past bleaching events show coral reefs can recover if thermal stress does not last for prolonged periods.

If mass bleaching does occur, the authority would study its extent and impacts, alongside coral reef scientists from the Australian Institute of Marine Science, James Cook University, the University of Queensland and the CSIRO.

Blair Palese, chief executive of 350.org said the "tragic coral bleaching" showed coal and gas were "warming the planet and destroying the places we love most".

The authority says bleaching occurs when stress causes corals to expel tiny marine algae called zooxanthellae, which live inside their tissue and provide corals with much of their food and colour.
Without zooxanthellae, the coral tissue appears transparent, revealing the coral's bright white skeleton.

SOURCE