Philippines: Large-scale coral reef study reveals ‘troubling’ picture

Wilfredo Y. Licuanan Malaya Business Insight 11 Nov 11;

THIS time, they were ready.

Unlike a similar event in 1998, the 2010 mass coral bleaching happened when a reef monitoring research system was in place in key locations around the country.

Called the Remote Sensing Information for Living Environments and Nationwide Tools (RESILIENT) for Sentinel Ecosystems in Archipelagic Seas (SEAS), the large research program on climate change in coastal zones is funded by the Department of Science and Technology.

It involves the Marine Science Institute of the University of the Philippines (UP) Diliman, UP Visayas, Bicol University, Xavier University (Cagayan de Oro), Mindanao State University (Naauan) and De La Salle University (DLSU).

The three-year research, which ends in 2012, involves more than 20 local governments, organizations and agencies. DLSU’s Marine Station in Lian, Batangas, was part of MIRROR (Monitoring and Impact Research on Resilience of Reefs) that monitored reefs in six locations selected to represent different climates.

More than 20 RESILIENT SEAS studies related to climate change were presented during the 11th National Symposium on Marine Science convened by the Philippine Association of Marine Science.

The year 2010 was marked by a cold phase ("La Niña") of yet another El Niño-Southern Oscillation (ENSO) cycle that began a year earlier; ENSO causes the inter-annual warming or cooling that occurs across the tropical Pacific Ocean.

The cold phase actually meant anomalous warming of the waters around the Philippines from April to December 2010, staying the longest around the South China Sea/West Philippine Sea basin where temperatures in excess of 3o Celsius above normal were recorded.

One major reason coral bleaching happens is that the sea water is warmer 2 degrees above normal that persists for one to two weeks. In the Philippines, the temperature ranges from 25 o C in March and February to about 29o C in summer.

There is no coral bleaching when sea temperature is normal. Now we are on the throes of another warming. While 1998 was the worst in recent memory, 2010 was even worse.

The last time a long term temperature anomaly of this scale was observed was at the end of the 1997-1998 ENSO cycle, an event that was also marked by widespread coral bleaching.

In 2010, coral bleaching and its impacts were most distinct in Talim Bay, in Lian, Batangas, and in Cangaluyan Island in the Bolinao-Anda reef system in Pangasinan.

Data on corals were collected from images taken with digital cameras. The fate of individual coral colonies were tracked while growth, shrinkage or coral deaths were measured.

It was an unprecedented insight into the causes and impacts of bleaching, and the future of Philippine reefs.

It paints a troubling picture of what is happening in Philippine waters. It also shows that concerted action can save and is saving some of the best coral reefs.

Winners, losers

Despite decades of cutting-edge research, coral reef monitoring is still in its infancy in the Philippines.

The two most monitored reefs in the Philippines are off the Br. Alfred Shields Marine Station and the Bolinao-Anda reef system in Pangasinan (site of the UP Bolinao Marine Laboratory).

Data suggests both reefs are declining, and coral bleaching is not the only cause.

In Bolinao, few corals are left alive in the six sites being monitored. Average coral cover as of April 2011 was 8.9 percent, compared to the 10.8 percent in May 2009 when monitoring started. And it is far from the 30 percent to 50 percent observed in the 1970s.

The corals in Lian fared better, with average coral cover of 19 percent in April. While this is two times higher than in Bolinao, the loss of coral cover was more abrupt in Lian – a loss of 6 percent coral cover during the summer of 2010; it occurred before the bleaching in May that year.

Marine scientists are trying to relate these patterns in the life of the coral populations to events such as ocean warming and storm impacts.

In Lian, all staghorn corals and brown stem corals were dead by the summer of 2010. These corals are among the most sensitive to ocean warming; the Acropora is also the preferred food of the crown-of-thorns sea star.

The relatively resistant Porites coral did much better. Most of those alive in April 2011 are small fragments which can grow a few meters across. Unfortunately they lose tissues and shrink during stressful conditions.

Based on the 2009 rate of decline, Porites should disappear from Bolinao-Anda area by 2029.

This is disturbing because Porites is a major coral builder and is the most common coral (along with Acropora) in the fringing reefs that surround large islands in the Philippines such as Luzon, Mindanao and Samar.

Without Porites, the reefs in Bolinao-Anda will be as good as dead.

Remember that Porites is not as sensitive to coral bleaching as other corals, and is among the last to be attacked by the crown-of-thorns.

But even this coral survivor will not likely last for long.

There are already signs that La Niña will start again in 2011 which may mean another bleaching episode. And the crown-of-thorns sea stars are still common in many reef areas.

The Lian and Bolinao-Anda reef studies warn us that we will definitely have fewer coral reefs in the future, and there will be fewer coral species represented in the remaining ones.

Not all is lost, however. While Porites corals may have disappeared in Lian, these same corals even now makes up the most abundant coral family in the Tubbataha Reefs, where it covers large portions of the reef slope.

Like the coral reefs in Bolinao-Anda and Lian, those in Tubbataha experienced severe ocean warming, with temperatures of above 29o C persisting for at least 246 days in 2010 (compared to 198 days in Lian and 217 days in Bolinao-Anda).

And the crown-of-thorns sea stars have also decimated some sections of the reefs.

Near the Lian site, a large group of crown-of-thorns sea stars killed about one in 10 of the corals.

This clearly shows that the rapid decline in coral cover in the shallower monitoring station, where 15 percent coral cover was lost, may be due to crown-of-thorns sea stars – even before bleaching started.

Some corals can endure bleaching and crown-of-thorns sea stars. In Bolinao, the blue coral is the most common, making up 35 percent of the coral cover, and are never seen to have been attacked by crown-of-thorns sea stars. And very few of the blue coral reefs have been observed to bleach.

So it is that the Philippines can thrive despite coral bleaching and crown-of-thorns outbreaks. We just have to make sure though that reef stresses are reduced, which requires that fishing is managed, sedimentation and pollution is controlled, and crown-of-thorns sea stars are kept to a minimum.

Tubbataha teaches us that entire reef systems can thrive despite the challenges posed by ocean warming, coral bleaching and even crown-of-thorns outbreaks.

The Porites in the Lian plots show that some coral species can somewhat endure these same challenges even with the added burdens brought by overfishing, sedimentation and even some pollution.

To save the remaining reefs, we must begin by reviewing current management and conservations efforts and answering some hard questions.

Are the existing protected marine parks large enough? Are they in the right places? Will they function alone, or do we need to have a connected, coordinated network? The work continues. ScienceNewsPhilippines

(Dr. Wilfredo Y. Licuanan is the Head of the Br. Alfred Shields Marine Station in Lian, Batangas, and Professor at the Biology Department, College of Science, De La Salle University Manila.)