The maximum recorded temperature in Hawaii is the lowest of all the states in the US. “That can’t be true”, I hear you say… “what about Alaska?”. Actually you’re right, Alaska shares the bottom spot with Hawaii which just helps prove the point that it never gets too hot in Hawaii. As the travel brochure explains, it gets beautifully warm but never unpleasant, cooled by the deep oceans that surround it.
So when we heard, a couple of weeks ago, that warm ocean waters were causing a coral bleaching event in Hawaii the alarm bells immediately went off. Even in the global bleaching events of 1997 and 2010, Hawaii remained cool and virtually unaffected.
A coral bleaching event occurs when ocean temperatures and sunlight exposure exceed the tolerance levels of corals for a number of weeks. The algae that gives the coral its colour and on which it depends for food, becomes toxic and is expelled, leaving the coral naked and bright white. If the temperature doesn’t fall within a couple of weeks, allowing the algae to return, the coral dies.
We visited Hawaii to see the bleaching event for ourselves with the aim of assessing it’s significance. Even as we pulled up to the dock at the Hawaiian Institute of Marine Biology, on the iconic Coconut Island, it was clear how severe the bleaching was. The bright white corals were clearly visible everywhere.
We decided to join the local assessment team as they carried out surveys in Kano’ehe Bay. There aren’t many places in the world where there is a coral rapid response team already in place and able to respond to an event like this. Their name isn’t rapid; the Department of Land and Natural Resources Division of Aquatic Resources Coral Rapid Response Team ( DLNR DAR CRRT for short!) but they were clearly fast at monitoring the situation, immediately taking us to some of the worst affected areas.
The sight we were greeted with underwater was depressing. It looked sick, really sick. Not just white but every shade of muddy yellow. Even the presence of a large green turtle couldn’t make this reef look good. We’ve seen a lot of sick reefs on our global survey, but rarely do they appear as sick as they really are – they can still look fine to the untrained eye. But here there was no such confusion.
The following day we headed to the iconic Lanikai Beach where there was even greater bleaching. We walked past the oblivious sunbathers on the beach, swam 50 metres and found ourselves in a pure white world. Huge corals, hundreds of years old, were ice white. In contrast to the previous day, these were hauntingly beautiful. A sight I won’t ever forget.
Unfortunately the situation is looking far worse in the Northern Hawaiian islands. There the bleaching was even more intense. In fact it was quite literally off the scale. But being 1000km from the nearest tourist beach, this bleaching went largely unreported.
Time will only tell whether the Hawaiian corals will recover. Many will likely die. However there is cause for some optimism in Hawaii’s main islands. Three days before we arrived, there was a minor hurricane. The same heat that causes bleaching often causes tropical storms. This can be a two edged sword if the storm is too powerful, but in this case, it wasn’t strong enough to damage the coral, just strong enough to bring in some cooler water. Also the corals had been well prepared; enormous local efforts had been made to remove an invasive weed in the area and to reintroduce hundreds of thousands of sea urchins. Without these efforts, the situation would be far worse.
The bleaching event in Hawaii could have been worse. But that misses the point. The fact is an area naturally sheltered from the impacts of our rapidly warming oceans has just suffered a major bleaching event. Only the second one on record. Is this a indicator of what is to come for other more vulnerable areas? Have our oceans warmed so much that even a minor El Nino could cause a global bleaching event? It’s looking increasing likely that we soon find out.