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Biodiversity Research Continues in Pag-asa Island, West Philippine Sea

May 9, 2025
Mandaragat News, Stories

FEATURED PHOTO: The April 2025 Pag-asa Island Expedition Team. (Left to Right, Top to Bottom) Lorenz Cajilig, Hannah Grace Siena (DENR-BMB), Claude Michael G. Salva, Fernando Castrence, Jeffrey Munar, Aubrey Abadiano, Kametchi Anne Blancaflor, Gizelle A. Batomalaque, Fernando P. Siringan (Chief Scientist), and Dale Patrick Atup.

A team of 10 researchers from the UP Marine Science Institute and DENR-Biodiversity Management Bureau (DENR-BMB) recently returned from a field survey on Pag-asa Island in the Kalayaan Island Group, West Philippine Sea, conducted from April 25 to May 3, 2025. This field-survey builds on their February 2025 survey, now reaching areas that were previously inaccessible due to large waves. The team continued to explore the invertebrate biodiversity, map the reef’s substrate types, and measure water movement and key physicochemical properties over the reef flat. Coral and fish assessments were also carried out, and long-term monitoring stations on the fore reef were revisited. Additionally, samples of Heliopora coerulea (blue coral) were collected for a population genetics study, which aims to reveal how connected—or isolated—Pag-asa’s blue coral populations are from others across the country.

This work is part of the DENR-BMB-funded BioConSeq-WPS (Integrated Research for Biodiversity Conservation and Carbon Sequestration in the West Philippine Sea), a long-term effort to understand and protect marine ecosystems in this ecologically critical area. The Philippine Air Force provided the transport back to Metro Manila and the Presidential Office for Maritime Concerns (POMC) coordinated support across government agencies.

Fish Visual Census was used in documenting the diversity and abundance of fish on the reef flat and the fore reef.
Coral cover survey using the photoquadrat method along the break of slope of the fore reef on the south side of the Pag-asa Island Reef.
A school of juvenile fish at the break of slope of the fore reef on the NE portion of the Pag-asa Island Reef.
The coral cover on the fore reef is sparse due likely to multiple stressors such as episodes of elevated water temperatures, outbreak of Crown-of-Thorns starfish, passage of typhoons, and destructive methods of fishing.
The middle portion of the reef flat has a higher coral cover where Heliopora dominates over other hard corals.
Collection of samples of Heliopora for population genetic analysis.
A close-up photo of Heliopora sp. showing white “furry” protrusions. This unique appearance is owed to its polyps with octamerous symmetry.
A giant clam (Tridacna sp.) wedged between brain corals in the reef flat.
A flower sea urchin (Toxopneustes pileolus), an extremely venomous species of sea urchin, showing its spherical body covered by flower-like pedicellariae.
A sea urchin (Echinotrix diadema) hiding in the coral rubble. This urchin can be identified by the green tint of its spines.