By Ellalyn De Vera-Ruiz
Marine conservationists are working to find coral reefs that have recovered from bleaching as these could potentially be the “hope spots” that can save Philippine reefs.
“We not just aim to map the extent and severity of the coral bleaching incidence and other reef stressors around the Philippines but we also want to identify areas that have recovered from bleaching because these are the areas that are most likely more resilient than others,” Philippine Coral Bleaching Watch (PCBW) social media administrator Erina Pauline Molina said during a recent webinar organized by the Department of Environment and Natural Resources’ (DENR) Biodiversity Management Bureau.
Molina, who is also a National Geographic explorer, said the identification of most resilient reefs should be done immediately to provide them protection.
“The academe or the DENR cannot do it alone. We all need to come together to search our reefs of hope around the Philippines,” she said.
She urged the public to document possible coral bleaching or report the occurrence of reef stressors in their areas, as reports from the general public are consolidated and verified by marine experts.
She stressed that the power of citizen science helps marine scientists capture a bigger picture of bleaching event around the country.
The PCBW regularly updates its social media account with coral bleaching alerts issued by the United States’ National Oceanic and Atmospheric Administration that shows the coral bleaching hotspots for the past 30 days.
“This could provide us guidance in identifying stress levels in different parts of the Philippines,” Molina pointed out.
A yellow warning indicates that coral bleaching is likely to progress in that particular area; an orange warning indicates that there is possible bleaching; a red warning or Alert Level 1 indicates that bleaching is likely happening; while a maroon warning indicates that coral mortality is likely in these areas, she said.
“But since these are just based on modeling techniques, there is still a need to verify what is happening on the ground,” she added.
To date, PCBW has received at least 500 reports of possible coral bleaching from about 100 citizen scientists.
Hope for bleached corals
The country’s rich marine ecosystem is continuously under threat because of climate change impacts, Molina said.
She noted that there have been three global bleaching events occurring in 1998, 2010, and 2015. “These are also reflected in our coral bleaching observations in the Philippines with the most number of observations in 1998, 2010, and 2016,” she said.
PCBW coordinator Miledel Quibilan in an e-mailed interview said coral bleaching is caused by anomalously high sea surface temperatures (SST) and high solar radiation.
The extent of damage to corals is determined based on a number of factors–how anomalously high the sea temperatures are at a particular time; how long the high SSTs remain in an area (from days to weeks to months); and if the coral reef area consists of coral species that are sensitive to high temperatures. “If this is the case, then you can expect more bleaching and possibly high coral mortality,” Quibilan said.
“When corals bleach and if it cannot recover within a few months, these corals die, destroying the habitat of our marine fishes,” she added.
But there remains hope that bleached corals can recover. Molina said bleached corals are not dead but are dying.
“Corals can still recover after they have bleached. But they lack nutrition because they rely on their symbiotic zooxanthellae for food. They bleach because they expel their symbiotic zooxanthellae as a stress response. They recover when they re-acquire a new set of zooxanthellae from the water column. If they fail to do this, then the more completive algae will grow on them and the corals die,” Quibilan explained.
While we cannot control the occurrence of thermal stress events and the occurrence of massive coral bleaching, Quibilan emphasized that local management efforts can be done to aid the recovery of coral reefs after coral bleaching events.
She added that long-term resiliency should be built by establishing a network of marine protected areas and managing for chronic stressors, such as sedimentation, pollution, overfishing, and removal of known coral predators such as crown of thorns starfish.
For them to recover, Molina said the corals have to be in the best favorable condition and reef stressors should be minimized.
She cited studies showing possible coral recovery within three to six months.
“But at business-as-usual scenario, bleached corals tend to die in the long run if they continuously face these stressors. When this happens, the change is already irreversible,” Molina said.
“This shows that there is still hope for out reefs that are experiencing bleaching if they are managed properly,” she added.