A bleached Great Barrier Reef

 In Coral Bleaching, global warming, Great Barrier Reef, Weather

If you have been following marine oriented news sources in the last six months, you will have noticed a tremendous increase in bad news about the Great Barrier Reef. The biggest problem this reef faces now is coral bleaching. Coral bleaching is a worldwide problem that doesn’t only occur on the Great Barrier Reef. The Maldives is following, with 60% of the reef now affected by bleaching.

The bleaching started at one part of the reef only, but have spread out afterward. Through aerial surveys researchers have found out that about 93% of the Great Barrier Reef that has been observed has been bleached and 35% had died or is dying. South of Cairns, the most popular part of the reef for tourists incidentally, only 5% has died so far. At the beginning of June part of the reef looked very bad. It is estimated that about a quarter of the total reef has died. (link takes to you sad pictures)

Bleaching occurs when sea temperature rises up to such a level that the coral struggles to survive. One defense mechanism is to get rid of its zooxanthellae, the algae they live with in symbiosis. By expelling the algae, the coral also deprives itself of about 90% of its food source. The algae use photosynthesis to turn carbon dioxide and light into glucose ad oxygen. The other 10% of its food the coral collects by itself by catching plankton by moving its tentacles in the water. Besides the food production, the zooxanthellae are also responsible for most of the color of the coral. That’s why bleached coral looks either white or very lightly colored. Bleached coral can survive up to a few weeks and can collect new zooxanthellae in the water, but only if the problem of the high water temperature disappears. If the water temperature stays the same, the coral will eventually die. See also the NOAA diagram on bleaching. The water temperature measured in the second quarter of 2016 were the highest since the recording started in 1900.

At Marine Conservation Philippines we have our fair share of Australian volunteers who express great concern over the situation at home. The good news is that reefs can recover from bleaching given enough time. This has however been the third mass bleach event of the Great barrier Reef in 18 years and that is a lot of bleaching in such a short period. New coral recruitment has to settle on the dead coral again and over time they will slowly grow. In ten years, soft coral and the fast growing Acropora species are back again, but other corals take years to regrow. So far, the water temperature has increased only one degree. If there are too many human threats, the reef gets less resilient, meaning it is harder for a reef to recover and turn back into a fully healthy reef. Unfortunately, bleaching is not the only threat. Agricultural run-off, pesticides, siltation, dying mangroves and a government that partially ignores the problem are not helping the recovery of the reef either because it has to overcome all the threats of all these pressures at the same time.
Unfortunately, the Australian government needs to be more aware of the seriousness of the problems that are now occurring at the Great Barrier Reef. The UN produced a climate change report last May which initially contained references to the reef, but the government asked if the examples could be removed, because ‘the information could harm tourism‘.

It is estimated that $10 bn is needed to reduce water pollution and to keep the reef in good health. Fortunately enough researchers and other interested people acknowledge the problems and lobby to do something about it. In a sad story, Tourism is actually increasing, because people are afraid they might otherwise be ‘too late’. Hopefully that’s not the case and the reef will recover from the bleaching event.

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