Madagascar Reefs May Hold Keys to Rebirth, Despite Bleaching

Divers examine bleached coral reefs off the African island of Madagascar during a recent survey. Bleaching occurs when warming seas kill the algae that live inside corals and give them food and color. The survey found that up to 99 percent of some of the reefs had been bleached. Photograph courtesy Blue Ventures


Madagascar Reefs May Hold Keys to Rebirth, Despite Bleaching
James Owen
for National Geographic News
October 17, 2006

Though blighted, coral reefs discovered off Madagascar may provide the seeds of recovery for marine life devastated by rising sea temperatures, researchers say.
A survey of coral reefs along the African island nation's remote southwest coast has revealed massive damage from coral bleaching—the loss of algae that live within corals and provide them with both food and color (Madagascar map, facts, and music).
Some areas were found to have lost up to 99 percent of their coral cover. But researchers also discovered pockets of bleaching-resistant corals. The scientists say these animals could help revitalize dying reefs.
"To find these little foci of resistance is extremely rare and is of massive conservation importance," zoologist Alasdair Harris said.
Global Warming
Harris is research director for the London-based marine conservation group Blue Ventures. The organization led the survey in partnership with the Bronx, New York-based Wildlife Conservation Society.
He says the survey shows the importance of locating and protecting healthy coral ecosystems.
"As climate change poses an increasing threat to our marine habitats, these resilient areas could hold the key to ensuring the continued existence of coral reefs around the world and the marine species that rely on them for survival," he added.
The team found that, as in other regions of the Indian Ocean, coral reefs are dying off southwest Madagascar. (Related: "Global Warming Has Devastating Effect on Coral Reefs, Study Shows" [May 16, 2006].)
Bleaching—so called because the corals turn white—affected 75 percent of coral reefs around the world in 1998, according to the United Nations Environment Programme. The Indian Ocean was badly hit in 2000 too.
"There has been mass mortality relating to hot sea surface water," Harris said.
Madagascar, the world's fourth largest island, is renowned for its wealth of unique plants and land animals, including lemurs, fossas, and giant jumping rats. Less known is the diversity of marine life around its shores. (Related: "Coral Trove Found Off Madagascar" [May 15, 2002].)
Madagascar, the world's fourth largest island, is a nature-lover's paradise on land, but its underwater treasures are only now being explored, yielding up previously unknown species of coral and fish.
A recent one-month marine survey more than doubled the number of corals previously thought to exist in island waters and identified several new species of fish and as many as nine new corals.
"Madagascar gets a lot of attention for its biodiversity on land, but its marine habitats are equally precious and threatened," said Dr. Sheila McKenna of Conservation International, the Washington, D.C.-based non-profit organization that sponsored the research.
Located 250 miles off the eastern coast of Africa, the island is slightly less than twice the size of Arizona yet has six different microclimates ranging from rain forest to desert. It hosts nine-tenths of the world's lemur population, 1,000 different orchid species and more than 10,000 varieties of plants with new ones being discovered daily. Its Eden-like diversity has made it a number one priority in international conservation efforts, but now the reefs surrounding the island like lacework are moving up on the list of marine biodiversity hot spots.
"The diversity of corals was much larger than I had expected," said Dr. John Veron, chief scientist at the Australian Institute of Marine Science and a member of the international research team.
Coral are tiny spineless animals essential in building reefs, one of the planet's oldest and most complex ecosystems. Supporting 25 percent of all marine life, many reefs around the world are threatened today by both man and nature.
Donning scuba gear, the researchers surveyed 30 sites off the northwestern coast, documenting 304 coral species, some found on reefs no bigger than a few hundred yards. The number of coral described during the 20-day expedition in January comes close to the 340 species recorded for the entire western Indian Ocean and suggests that the island and the nearby Comoro Islands have the highest number of corals in the region. Dr. Veron discovered all the coral not previously identified.
"Finding nine to ten new species of corals is about the yearly quota, but for one person to fulfill this quota is quite unusual," said Stephen Cairns, a curator of coral at the National Museum of Natural History in Washington, D.C.
Dr. Veron, who has discovered and described over one-quarter of all reef coral, was surprised himself.
"I rarely come to a place where there are undescribed species. Usually if it's new to me, it means that it is a new species, but that doesn't mean some Frenchman didn't see them in 1880," he said. He was particularly amazed to discover one spectacular coral "like a bowl of flowers, with mostly red flowers but also some blue and green."
More research will be needed before the samples are accepted as new species, because classifying coral is as much an art as a science.
"Corals are like trees, they can change their appearance depending on where they grow. They can look different in shallow and deep water and on the coasts of other countries," Dr. Veron explained.
The survey also found a richer diversity in fish than anticipated and what may be three new species of damselfish.
"Two of these three fish got me very excited because I have studied this family for more than 30 years," said Gerald Allen, Ichthyology and Science team leader for Conservation International's Marine Rapid Assessment Program. "There are 350 species worldwide and I know them all like the back of my hand. I immediately recognized two of these three as new." The third may have been masquerading as another species, he suggested.
Cataloguing new species was only one goal. The expedition also collected socio-economic and biological data to help develop reef-protection policies. The researchers interviewed local fishermen and considered reef health. They found great ecological awareness and little evidence of coral bleaching, related to increased water temperatures.
"The state of these reefs was surprisingly good," Dr. Veron said. "Within 50 years, coral reefs around the world will be decimated, but I think the Madagascar reefs will be largely protected from the effects of global warming because of cold currents from the Southern Indian Ocean. If these reefs are looked after, in 50 years they will be there."