Phillipines: El Niño causing coral bleaching on Tubbataha Reefs

Ellalyn De Vera Manila Bulletin 16 Sep 15;

Rising sea temperatures triggered by the current El Niño is causing coral bleaching on Tubbataha Reefs. And with scientists predicting a major El Niño that may last until mid-2016, coral reefs in the Tubbataha Reefs Natural Park (TRNP) are braced for more trouble.

In an exclusive interview with the Manila Bulletin, Tubbataha Management Office (TMO) research assistant Jeric Decujos said the coral bleaching was first reported by the Tubbataha marine park rangers in July on dive sites Amos Rock, South Park, and in areas around the Bird Islet in the North Atoll.

Bleaching was also observed in dive sites Black Rock and Delsan Wreck in the South Atoll, and the Jessie Beazley Reef in the northernmost part of TRNP.

“Bleaching could be attributed to a number of factors, such as sedimentation, changing pH (acidity/alkalinity), pollution, pathogens, and increasing/decreasing water temperature,” Dejucos said.

“Because of the evident and contemporaneous El Niño phenomenon, and similar documented cases in other parts of the Pacific, we are pinning this bleaching in Tubbataha to rising seawater temperatures, hence this is an El Niño-induced bleaching,” he pointed out.

HOW BLEACHING OCCURS

Dejucos said most corals live in a symbiotic relationship with photosynthetic algae called zooxanthellae, which lives inside their tissue. These algae are the ones that give corals their color since coral tissues are almost transparent, he added.

“As animals, corals need organic materials and oxygen to respire and continue living. These materials are supplied to them by the zooxanthellae as byproducts of photosynthesis that is why corals need sunlight to live even if they are not plants. In return, corals supply carbon dioxide and water to its algae symbiont, which are used to carry out photosynthesis for the nourishment of its own,” he said.

“When there is an abnormal increase/decrease in temperature and light intensity, these zooxanthellae somehow become inefficient and begin to produce harmful reactive oxygen that damages the cellular structure of its coral symbiont. This is what compels corals to expel the algae. When the algae is gone, their source of nourishment will decrease but not completely gone because like us, they store lipids and they can filter out plankton in the water as another source of food and they will turn back to their ‘true’ color, white,” he explained.

However, Dejucos said “bleached” corals do not die immediately, “but the loss of their symbiont algae makes them susceptible to diseases and drives them to starvation, which in the long run, could spell death.”

“Corals can bounce back. They can repopulate the algae inside them when conditions go back to a bearable and tolerable state,” he pointed out.

But Dejucos noted that what makes the situation “alarming” is the consensus among climatologists and meteorologists that the present El Niño will continue to perpetrate until the first half of 2016. “This means that the breathing room for corals for them to be able to bounce back, is nowhere near,” he stressed.

Based on TMO’s scientific researches conducted in March and April, before the bleaching occurred, TRNP is on an “outstanding condition.”

The TMO researcher cited that fish biomass are estimated to be at 343 metric tons per square kilometer (mt/sqkm). “In the Philippine setting, 40 mt/sqkm is already considered a very good/healthy reef. You cannot produce numbers like 343 mt/sqkm if your corals are not in a good, if not best condition,” he said.

“If present conditions persist and worsen, in the long run, it will take its toll on the fishing industry of Palawan and to those places whose fishing industries are highly dependent on Palawan,” he also said.

Based on an ocular inspection conducted by marine experts last September 5, the bleaching has affected 0.006 to 0.009 percent of every 25 square meters or 5 by 5 meters of the 97,030-hectare TRNP.

“For now, there is no exact figure to quantify how big/how small the affected areas are,” Dejucos said.

ADDRESSING THE PROBLEM

He noted that the bleaching we are experiencing is attributed to El Niño, which is a worldwide and large-scale event, thus “controlling” the effects is almost impossible.

“What we do, as we always do with or without bleaching, is continue to protect the park from illegal activities and pollution which could add up to the agony that the corals are currently experiencing. It is like when you are suffering from an allergy and you don’t have an antihistamine at hand at the moment, the first thing to do is step away from the allergy triggers,” Dejucos said.

“If there is a healthy and clean ecosystem, corals will build their resilience around that. We are planning to conduct an assessment using Reef Check methods this October to have a better vision of what is going on,” he added.

TRNP also suffered bleaching in El Niño years 1998 and 2010. “However, El Niño was more frequently recorded in the Philippines than those mentioned periods, meaning that coral reefs of TRNP has built resilience to resist bleaching during other times of El Niño. Because of its resilience, corals were able to recover from the said bleaching events,” he said.

Tubbataha was inscribed by UNESCO as a World Heritage Site in 1993. It was recognized as one of the country’s oldest ecosystems, containing excellent examples of pristine reefs and a high diversity of marine life. It is also an important habitat for internationally threatened and endangered marine species.