Massive coral mortality following bleaching in Indonesia

Aug 17, 2010

The Wildlife Conservation Society today released initial field observations that indicate that a dramatic rise in the surface temperature in Indonesian waters has resulted in a large-scale bleaching event that has devastated coral populations.

WCS's Indonesia Program "Rapid Response Unit" of was dispatched to investigate bleaching reported in May in Aceh-a province of Indonesia-located on the northern tip of the island of Sumatra. The initial survey carried out by the team revealed that over 60 percent of corals were bleached.

"Bleaching"- a whitening of corals that occurs when algae living within coral tissues are expelled - is an indication of stress caused by environmental triggers such as fluctuations. Depending on many factors, bleached coral may recover over time or die.

Subsequent monitoring conducted by marine ecologists from WCS, James Cook University (Australia), and Syiah Kuala University (Indonesia) were completed in early August and revealed one of the most rapid and severe coral mortality events ever recorded. The scientists found that 80 percent of some species have died since the initial assessment and more colonies are expected to die within the next few months.

The event is the result of a rise in sea surface temperatures in the Andaman Sea - an area that includes the coasts of Myanmar, Thailand, the Andaman and Nicobar Island, and northwestern Indonesia. According to the National Oceanic and Atmospheric Administration's Coral Hotspots website, temperatures in the region peaked in late May of 2010, when the temperature reached 34 degrees Celsius—4 degrees Celsius higher than long term averages for the area.

"It's a disappointing development particularly in light of the fact that these same corals proved resilient to other disruptions to this ecosystem, including the Indian Ocean Tsunami of 2004," said WCS Indonesia Marine Program Director Dr. Stuart Campbell.

WCS and JCU have been working in the region since March 2005. Surveys conducted in the wake of the Indian Ocean Tsunami in 2004 revealed that the many reefs of Aceh were largely unaffected by this massive disturbance. Indeed, reefs severely damaged by poor land use and destructive fishing prior to the tsunami had recovered dramatically in the intervening years due to improved management. Government and community-managed areas in the region have been remarkably successful at maintaining fish biomass despite ongoing access to the reefs. But the bleaching and mortality in 2010 have rapidly reversed this recovery and will have a profound effect on reef fisheries.

Of particular concern is the scale of the sea surface temperature anomaly which the NOAA website indicates has affected the entire Andaman Sea and beyond. Similar mass bleaching events in 2010 have now been recorded in Sri Lanka, Thailand, Malaysia and many parts of Indonesia.

"If a similar degree of mortality is apparent at other sites in the Andaman Sea this will be the worst bleaching event ever recorded in the region," according to Dr. Andrew Baird of the ARC Centre of Excellence for Coral Reef Studies at JCU. "The destruction of these upstream reefs means recovery is likely to take much longer than before".

"This is a tragedy not only for some of the world's most biodiverse coral reefs, but also for people in the region, many of whom are extremely impoverished and depend on these reefs for their food and livelihoods," said WCS Marine Program Director Dr. Caleb McClennen. "Immediate and intensive management will be required to try and help these reefs, their fisheries and the entire ecosystem recover and adapt. However, coral reefs cannot be protected from the warming ocean temperatures brought on by a changing climate by local actions alone. This is another unfortunate reminder that international efforts to curb the causes and effects of climate change must be made if these sensitive ecosystems and the vulnerable human communities around the world that depend on them are to adapt and endure."

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andyd
2.5 / 5 (4) Aug 17, 2010
And not a mention of the El Nino conditions.
pres68y
3.7 / 5 (3) Aug 17, 2010
-or mention of the major problem of US Navy
super powered sonar scanning that ruptures
the fine membranes of the coral creatures.
Navy won't even admit to rupturing the
fragile sensor organs of massive whales!
gmurphy
3.7 / 5 (3) Aug 17, 2010
@andyd, El Nino is not typically associated with temperature rise in the waters around Indonesia. http://en.wikiped.../El_Nino
andyd
3 / 5 (2) Aug 17, 2010
Ah, who could argue with Wikipedia. A PBS Nova article suggests one possible cause of El Nino is "Some say it begins when strong west-blowing winds near the equator-the trade winds-push against the sea, and drive sun-warmed surface waters against Indonesia and Australia. There the waters pile up like driftwood blown into a harbor."

The Wikipedia article does state that SST drop 2C around Indonesia during La Nina. So conversely, other times must be warmer, no?

bottomlesssoul
not rated yet Aug 18, 2010
I'm in Cambodia and do a lot of diving and snorkeling. We had a massive bleaching event at every dive site down to about 18 meters. A local research group is estimating about 20% mortality from surface to 10 meters.

Off the shore where I love to snorkel up to 50% have not recovered. It's devastating. Huge beasts about 8,000 years old and 3 meters across completely dead. They survived everything but this event.

And man alive, sometimes near shore we were measuring water temperatures of 36C. I would see a school of fish suddenly break apart because a pocket of hot water floated by before dispersing.

It was a drought too, worst in 50 years. Commercial shipping on the Mekong was shut down for months.

This was a rough summer in S.E. Asia, at least an 8,000 year event for some corals.
andyd
not rated yet Aug 18, 2010
I'm in Queensland, and familiar with bleaching events on the Great Barrier Reef. The reef *always* bounces back, and *always* to the amazement of the scientists who study it.