The Maldives is currently suffering the most serious incidence of coral bleaching since the major 1998 El Niño-event that destroyed most of the country’s shallow reef coral.
Coral bleaching is caused when rising water temperatures stress the coral, leading it to expel the algae it uses to obtain nutrients. When water temperatures rise even slightly, algae leaves the coral polyp and enters the water column, causing the coral to lose its colour and eventually die.
Reports of bleaching have been trickling in from marine biologists and researchers across the country.
Hussein Zahir from the Marine Research Centre (MRC) has been collecting reports of the bleaching, and said that based on his estimates, “10-15 percent of shallow reef coral is now completely white, while 50-70 percent has begun to pale.”
Senior Marine Biologist Guy Stevens, based at the Four Seasons Resort in Landaa Giraavaru, said that he had noticed that bleaching was beginning to occur last year “after a change in the weather linked to El Niño. The last one in 1998 was pretty catastrophic, and reefs in the Maldives have been recovering ever since.”
“It had a huge impact across the Indian Ocean, and the Maldives was most affected – pristine reefs suffered coral mortality rates of 95 percent,” Stevens explained. “At the time people were mortified and scientists were predicting the end of the reefs – coral is the foundation of the whole reef ecosystem.”
Since the devastating El Niño in 1998, marine biologists in the Maldives “have been holding their breath for the next one. In the meantime the coral has been slowly recovering. It was pretty depressing in 2003, but roll forward to 2010 and it’s starting to look good again. It recovers exponentially.”
Meanwhile, colleagues of Stevens based in Thailand, which escaped largely unscathed in 1998, have reported coral mortality rates “of up to 100 percent.”
“The hot spots move around, but they cover a big area and the coral here could easily take another hit,” Stevens commented.
Zahir noted that temperatures this year were following similar patterns to those of 1998, with a surface temperature in April of one degree above the long term average.
However the recent drop in temperature, brought on by rain and the onset of the southwest monsoon, has lowered the surface sea temperature and brought some relief, “and may give the coral time to recover.”
“Now the temperature has dropped from 32 degrees to 29-30 degrees, so hopefully things will improve. The conditions are right for the coral to become healthy again,” Zahir noted, however he emphasised the need for the tourism industry to assist with monitoring the bleaching.
“Here in the Maldives we have a vast reef area, and the MRC has very little capacity to do surveys. From the very beginning we’ve been running a bleach-watch reporting programme with the dive industry, but for some reason the feedback has been very disappointing. There’s a hundred resorts, but I can count on my fingers the ones who are working to raise awareness. I know it might impact on their marketing, but this needs to be documented.”
All the MRC required was GPS coordinates and an indication of how much bleaching was occurring, he explained.
In the meantime, both Stevens and Zahir noted that there was little that could be done to prevent further bleaching.
“There is very little we can do, especially in a resort environment, other than reducing human impact on the reef while it recovers – that means ceasing things like sand-pumping and beach renewal on a daily basis, while the reef is especially vulnerable to sedimentation,” Zahir explained.
Verena Wiesbauer, a marine biologist at Male-based consultancy Water Solutions, said she had just returned from visiting two islands in North Male’ Atoll and had documented heavy coral bleaching.
“The reefs had only just recovered, and now it’s struck again. It’s a big setback,” she observed.
“Fortunately it’s not as bad as 1998, and now the temperature is dropping. But I hope someone will keep track of the paling coral, to see if it gets its colour back.”
Wiesbauer added that the bleaching did not appear to have affected fish numbers yet, and suggested that “many fish don’t need live coral as long as the structure is there for them to hide in, and many algae feeders don’t mind [bleaching] at all. But there are some specialist coral feeders we need to watch for changes.”
Meanwhile, like Zahir, Stevens observed that the tourism industry appeared to have been in no hurry to report that bleaching was occurring.
“That’s something the resorts obviously don’t want to publicise,” Stevens commented. “But I don’t think it’s any good burying our heads in the sand, when there’s going to be no sand left to bury our heads in.”
The artificial coral breeding programs run at many resorts were well-intentioned, “but rather like putting a band-aid on a gushing wound.”
“It doesn’t address the issue. Rather [breeding programmes] are a tool to raise awareness and alleviate pressure on the local reef. But there are things like sand-pumping that resorts should halt during periods of bleaching because it makes the problem worse,” he said, concurring with Zahir.
“Otherwise there’s very little we can do – it’s really a global issue. We haven’t seen a reduction in fish life, turtles and mantas, and it seems those parts of the ecosystem can survive while the reef structure is at least in place, but overall I think we’re going to see a gradual decline. Coral reefs may be the first ecosystem we’ll lose on our planet.”
Images courtesy of the Marine Research Centre (MRC).