This year the Great Barrier Reef suffered the greatest mass bleaching event ever seen. Record warm temperatures turned large areas of the reef, a once vibrant 1400 km habitat, into a white boneyard.
Australian researchers have just shown that in the shallow water northern section 67% of the coral has died. Better news comes from the southern and central sections which show a 1% and 6 % coral mortality rate. The areas worst hit may need 10-15 yrs to recover…but with global warming it is possible we will see another bleaching event causing increased devastation in the hardest hit areas.
The importance of the corals reefs of the world is that they are comparable to the rain forests on land. The reefs cover only .1% of the sea floor , but house 25% of marine species. The y protect the land from storms, sustain food for half a billion people , and make for great diving and tourism spots.
Coral reefs are vulnerable to temperature changes, thriving within a narrow temperature range. In normal times coral polyps form a symbiotic relationship with zooxanthellae, a colorful algae that synthesizes sunlight and carbon dioxide to create nutrients for the reef. If the temperature gets too warm the algae goes into overdrive and produces toxins. The coral polyps then expel the algae from their tissue leaving the coral with that bleached look. Weakened, the coral is now susceptible to various diseases.
From January to March 2016 there were record high ocean temps thanks to global warming and El Nino causing mass bleaching in the Great Barrier Reef. Bleaching does not kill right away…if ocean temps drop the zooxanthellae will come back. If temps stay high for an extended period the coral will die from malnutrition and disease. When the coral dies the entire ecosystem is affected.
The good news is that even with a mass die off the coral can recover. The trick is that it takes years..10 , 15 , or even more yrs in higher stressed areas. With the current pace of global warming the reefs may not have time to recover before they get hit with a warming again. There is even a line of thought that believes that the Great Barrier Reef may lose it’s ability to bounce back as global warming continues.
Another issue is the amount of carbon dioxide we pump into the atmosphere…the oceans are becoming more acidic making the corals more sensitive to bleaching. To assist the corals we can also limit the amount of fertilizer and sewage runoff as these damage the corals as well. The key for us is the carbon dioxide emissions… global warming is a massive threat. I f we go past the 2 degrees Celsius mark we stand a good chance of losing half the world’s coral reefs.