Coral graveyards – revealing a hidden danger

Healthier coral - Baa Atoll

Healthier coral - Baa Atoll

Baa Atoll in the Maldives is the newest addition to the list of UNESCO World Biosphere Reserves – that means it’s up there with Ayers Rock, the Galapagos Islands and Niagara Falls in terms of its beauty and uniqueness, largely on account of its dozens of green islets and their fringing coral reefs. But this is not a wilderness area: seven of the largest islands are tourist resorts, whilst the majority of local people live on densely-populated ‘inhabited islands’ much of whose livelihood comes from fishing.

Moreover, the atoll’s coral is under threat. In April last year a second mass-bleaching event occurred as high sea temperatures swept the area, spurred on by global warming. This hit many of the reefs that were just beginning to recover from the devastating 1998 bleaching event, which killed 90% of corals in this area of the tropical Indian Ocean.

But not all reefs are affected equally, and to find out a bit more about this complexity I joined the marine biologist for Soneva Fushi resort, Kate Wilson, the oceans explorer and photographer Fabien Cousteau, and the film-maker Jon Bowermaster, in a snorkel tour of a couple of reefs which show very different impacts. We set out from Soneva Fushi – where we have all gathered for a high-level symposium on the future sustainability of the tourism industry – on a speedboat, skimming across the flat-calm surface of the Baa Atoll lagoon.

Both reefs are a good distance from any direct human impact, and should be in a relatively pristine state. The first however has suffered severely in the recent bleaching, and as Fabien Cousteau’s photographs show, is little more than a coral graveyard, with rubble and bare rock coated in slimy green algae. Some of the huge table corals had snapped off and tipped over, as if hit by some subsea disaster. The whole scene was eerie, with few fish visible even in the clear, bright water of the reef drop-off. In some spots the water felt like a hot bath, with the ‘thermocline’ between it and the cooler water below refracting the harsh sunlight at an odd angle.

Only fifteen minutes south-west, we stopped the boat at a second reef, this one washed by a strong current that made swimming difficult. Here the coral was in a much better state, as Kate explained – the brown-green table corals were growing strongly, whilst bare areas had some juvenile corals just beginning to sprout. An acropora stag-horn coral showed a white area, but she explained that this was not bleaching but had instead been sucked clean by a fat pincushion starfish, a culprit which still lurked nearby. Some other coral colonies fluoresced a startling neon blue, blending with the darker hues of an embedded giant clam. Fish were everywhere, far too colourful and varied to begin to describe.

So why the difference? Kate Wilson was not sure, but hypothesised that the second reef may have been kept cooler by stronger currents which would have reduced the pooling of the still, hot water that causes corals to bleach from thermal stress. Either way, these days management of coral reefs is essential, with a warning system in place when mass bleaching seems imminent – and in the meantime, no-take zones for fishing have been established: for the reefs to recover it is vital that herbivorous fish like parrotfish are allowed to graze to keep them clear of smothering algae.

This week all the resort managers and biologists are meeting to begin setting up a funding system to pay for the protection of the Baa Atoll reserve – this will begin operation in consultation with local people, so that managed fishing can go on in certain areas. Maldivians are proud that their fishing industry is one of the most sustainable anywhere – there are no purse seine nets or long-lines allowed here, and shark fishing has been banned throughout the country. Only pole and line fishing of yellowfin tuna is allowed, and is the basis of the nation’s second most important industry after tourism.

Making tourism more sustainable will be an even bigger challenge – all islands are currently powered by diesel generators, and visitors of course all arrive by air. But the national target of carbon neutrality is a serious one – another topic for the symposium here this week.

3 replies on “Coral graveyards – revealing a hidden danger&rdquo

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