Verde Island Passage coral reefs: research and restoration · Reef Map

The strait between Batangas and Mindoro, often called the centre of the centre of marine shore-fish biodiversity. Strong currents, mesophotic reefs and some resilient coral communities share the water with one of the country's busiest shipping and industrial corridors, and with the 2023 Princess Empress oil spill.

Geography and reef types

The Verde Island Passage (VIP) is the strait between southern Luzon and the island of Mindoro. Batangas State University's marine research centre describes it as a corridor shared by five provinces: Batangas, Marinduque, Oriental Mindoro, Occidental Mindoro and Romblon ³. It links the South China Sea in the west with the Sibuyan Sea and the inner seas of the central Philippines in the east. Strong tidal currents run through it, which helps explain both its high biodiversity and its sensitivity to anything carried in the water.

Most reefs in the passage are fringing reefs along the steep coasts of Batangas (Calatagan, Nasugbu, Lian, Mabini, Tingloy and Lobo), around Verde Island itself and along the northern Mindoro coast at Puerto Galera. There are also patch reefs and reef flats in sheltered bays, such as Talim Bay in Lian ¹³. Many reefs drop quickly into deep water. Mesophotic coral ecosystems below 30 m are known from Puerto Galera and Batangas, where technical divers from the California Academy of Sciences collected a new butterflyfish at 100–130 m ⁵. The passage also has shallow volcanic hydrothermal vents off Mabini, Batangas, where carbon dioxide seeps from the seabed ^22,23.

The Puerto Galera Biosphere Reserve covers 14,661 ha on the northern tip of Mindoro, bounded to the north by the passage. It was designated in UNESCO's World Network of Biosphere Reserves in 1977, and UNESCO lists coral reef conservation as one of its main tasks ⁷.

Biodiversity

The passage is famous because of one study. Carpenter and Springer (2005) analysed distribution data for 2,983 marine shore-fish species across the Indo-Malay-Philippine region. They found a peak of richness in the central Philippine Islands, and they called the islands "the center of the center" of marine shore-fish biodiversity ¹. Later Philippine papers apply that label to the Verde Island Passage specifically, and Horigue and Licuanan (2013, DLSU and UP) open their climate assessment by placing the passage "at the center of marine shorefish biodiversity in the Philippines" ^2,3. The UP Marine Science Institute notes that the VIP has a very high concentration of coastal fishes, corals, crustaceans, molluscs, seagrasses and mangroves. It also lists threatened species that use the area, including hawksbill turtles, whale sharks, manta rays, dugongs, humphead wrasse, giant groupers and giant clams ⁶.

Biodiversity work in the passage continues to add species. Rocha and colleagues described Roa rumsfeldi, a butterflyfish from mesophotic reefs at Puerto Galera and Batangas ⁵. A survey of nine sites in Batangas, Marinduque and both Mindoro provinces recorded 116 macroalgal species and nine seagrass species. That is about 12% of the country's recorded macroalgae and almost half of its seagrass species ⁴. New records continue to appear. In 2019 Sanchez-Escalona (Mindoro State University) reported the mangrove-associated sea slug Elysia leucolegnote from Calapan, Oriental Mindoro, the first record of the species in the Philippines ³³.

Condition and trends

Reef condition varies widely across the passage. Baseline surveys led by Batangas State University (BatStateU) compared marine protected areas (MPAs) with unprotected sites in four provinces ⁸. Average hard coral cover was 39.8% in Batangas MPAs and 38.8% at Batangas non-MPA sites. In Occidental Mindoro it was 49.5% inside MPAs and 32.3% outside. Oriental Mindoro showed the sharpest contrast: 25.0% inside MPAs and only 5.9% outside ⁸. The authors argue that unprotected reefs with good cover and many coral genera deserve protection too ⁸.

A second BatStateU-led study surveyed Occidental Mindoro, Marinduque and Quezon ⁹. Diumanod and Paluan in Occidental Mindoro had 47.3% and 32.6% hard coral cover, dominated by the blue coral Heliopora. Talao-talao in Quezon had 43.5% cover, dominated by Galaxea. Marinduque sites were much poorer, at 14.6% and 4.1% ⁹. The authors suggest that these less common reef types could become more widespread as seas warm ⁹. In western Calatagan, a 2024 study found hard coral cover of about 52% at Buntong Gasang Point and about 50% inside the Quilitisan MPA. Coral colour scores indicated normal symbiont densities at the time of the survey ¹⁴. Industrial frontage is in a different state. A community-led assessment off Barangays Ilijan and Dela Paz in Batangas City found only 0.1–6.2% hard coral cover ²⁰.

At the national scale, Licuanan et al. (2019, DLSU) found that Philippine reefs had lost cover over the previous decade, with very few reefs left in the highest cover category ¹⁰. Long-term data from community monitoring teams in the passage are more positive. The Malampaya Foundation reported that from 2013 to 2023, its VIP monitoring teams recorded a 44.25% increase in live coral cover and a 68.89% increase in target reef fish across permanent stations ³⁰. Its 2024 report gives a 241.54% average increase in reef fish abundance across its VIP and Oriental Mindoro sites ³¹. These are programme figures from partner-managed sites, not a passage-wide census.

Heat stress is a growing concern. NOAA Coral Reef Watch's "Central Philippines" regional virtual station is centred near the eastern end of the passage (13.95° N, 122.2° E). Its annual peak degree heating weeks were 9.1 °C-weeks in 1998, 11.8 in 2016, 15.1 in 2020 (the highest since 1985), 14.5 in 2024 and 11.3 in 2026 (our reading of the station data) ¹¹. NOAA links values above 8 °C-weeks with severe bleaching and significant mortality ¹². These are regional satellite figures, not reef-level observations. Some local communities may be better placed than this suggests. In Talim Bay, España, Licuanan and Aliño found coral communities dominated by bleaching-resistant species, with high recovery potential ¹³.

Threats

Shipping and oil. The passage carries heavy ship traffic to and from Batangas and Manila. In February 2023 the tanker MT Princess Empress sank off Naujan, Oriental Mindoro, carrying 5,660 barrels of industrial fuel oil ¹⁸. The UP Marine Science Institute used trajectory models and habitat maps to estimate that about 20,000 ha of coral reef, 9,900 ha of mangrove and 6,000 ha of seagrass could be affected. More than half of those reefs were in the Cuyo Islands ¹⁶. A later MSI bulletin forecast that some oil could move north into the VIP toward Calapan, Verde Island and parts of Batangas ⁶. A month after the sinking, DENR reported that 2,252 ha of coral in Oriental Mindoro had been affected. It also listed affected waters in Puerto Galera, Calapan, Batangas City and Tingloy ¹⁷. Fisherfolk in Naujan lost their income under fishing bans, according to interviews by Mindoro State University and partners ¹⁸. A 2026 study by DOST-ITDI, MSU-IIT and partners fingerprinted and tracked the weathering of the spilled oil from the wreck to the shore ¹⁹.

Industry and energy. Batangas Bay hosts ports, power plants and liquefied natural gas (LNG) terminals. The Center for Energy, Ecology and Development's 2022 assessment near the Ilijan LNG terminal and a proposed combined-cycle plant documented the very low coral cover noted above. It argued that new energy projects in the corridor need closer scrutiny ²⁰.

Nutrients, sediment and coastal development. As early as 1995, the UP Marine Science Institute linked nutrient-driven stress to changes in marine communities in a Puerto Galera coastal lagoon ²¹. UNESCO calls rapid and unregulated tourism development the biggest problem for the Puerto Galera reserve ⁷. In Talim Bay, sedimentation and nutrient loading were significant influences on coral communities ¹³.

Climate. Horigue and Licuanan projected losses of 3–22% in live hard coral cover from rising sea temperatures, because many reefs are rich in heat-sensitive acroporid and pocilloporid corals. They also projected losses of 12.5–37.5% from storms and 4–7% from sea-level rise ². Projected losses for reef fish were 9–16% of species richness and 12–54% of abundance ². The authors call these estimates conservative ².

Management and protected areas

The passage has many small, community-based MPAs rather than one large park. Batangas Province coordinates a provincial MPA network, one of the collaborative networks Horigue studied in her doctoral work at James Cook University ²⁵. Horigue et al. (2015, PLoS ONE) simulated seven ways the VIP's MPAs could expand. They compared uncoordinated local MPAs, coordinated partnerships among local governments, and systematic conservation planning. Systematic networks were more efficient in every governance setting. Unexpectedly, the uncoordinated scenario was slightly more efficient than the coordinated ones, with caveats. The authors still conclude that coordinated networks can outperform uncoordinated ones, especially when coordinated planning uses systematic methods ²⁴.

Batangas has also led integrated coastal management (ICM). In 1994 Batangas Bay became one of the first ICM demonstration sites in the East Asian Seas under the GEF/UNDP/IMO programme that later became PEMSEA ²⁶. The province set up its environment office in 1995 and a Batangas Bay Environmental Protection Council. In 1998 it opened the first environmental testing laboratory run by a Philippine local government. It received ICM Level 1 certification in 2015 and Level 2 in 2020 ²⁶. PEMSEA's 2026 account states that the province's current blue-economy work includes managing the VIP, sea-use zoning and port environmental standards ²⁶.

Fishers' views of MPAs are mixed. Samaniego and Rebancos (2019, UPLB) interviewed 209 fishers near young, mid-aged and old Batangas MPAs. Fishers reported that catches and fish sizes fell after the MPAs were set up. Even so, attitudes were positive, especially around older MPAs and where tourism jobs were available ²⁷. In 2023, Mission Blue named the passage a "Hope Spot", which raised its international profile ^3,15. Apo Reef Natural Park (15,799.23 ha), the large atoll-like reef west of Mindoro, is a legislated protected area under the Expanded NIPAS Act. It lies outside the passage proper but in the same Mindoro seascape ³².

Key research and studies

The biodiversity baseline. Carpenter and Springer (2005) established the central Philippines as the global peak of shore-fish diversity, the basis for the VIP's reputation ¹.
Climate vulnerability. Horigue and Licuanan (2013, DLSU and UP MSI) produced the first passage-wide assessment of coral and fish losses under warming, storms and sea-level rise ².
Planning for MPA networks. Horigue et al. (2015) is one of the few empirical tests of how far local MPAs can grow into an effective network ²⁴.
Province-wide surveys. The Batangas State University team, with Mindoro State University, Occidental Mindoro State University and UP Diliman, has published coral baselines across the VIP provinces ^8,9. Their macrophyte survey with Rula et al. extended this work to seaweeds and seagrasses ⁴.
Thermal resilience. España, Licuanan and Aliño (2015) assessed resistance and recovery potential of corals in Talim Bay near DLSU's Br. Alfred Shields FSC Marine Station in Lian, Batangas ^13,29.
Natural ocean-acidification labs. Reyes et al. (2022), with DLSU, UP MSI, MSU-Tawi-Tawi and NOAA, measured seawater pH from 6.12 to 8.09 at a Batangas vent site. Hard coral cover there was 14.8%, and 14 coral groups grew within 1 m of the most active plume ²². Maningas, Ticzon and Rodriguez (2025, UP) described coral communities at the Mabini vents ²³. These sites offer a preview of reefs under more acidic seas.
Oil spill science. UP MSI's real-time trajectory bulletins ^6,16, the socio-economic study of Naujan fisherfolk ¹⁸, and the 2026 source-fingerprinting paper ¹⁹ together document the 2023 spill.

Restoration work

Restoration in the passage has mostly involved coral transplantation alongside better MPA management. Starting in 2012, coral fragments were transplanted at sites across the country, including Mabini, Batangas. Samaniego et al. (2023, UPLB and SEARCA) surveyed fish five years later. Treatment sites in Mabini averaged 56 fish species per 250 m², against 43 at control sites, a significant difference. The authors caution that the effects of transplantation on fish are hard to detect without strong study design ²⁸. Batangas State University runs its VIP Corals programme and Marine Research Center from Batangas, with monitoring sites across the passage ^3,8. DLSU's Shields Marine Station in Lian provides a base for coral and seaweed fieldwork, with a reference collection of both ²⁹.

The strongest long-term results so far come from protection and enforcement, not from building reef. The Malampaya Foundation's community reef monitoring teams report that coral cover and target fish have risen at their VIP stations since 2013 ^30,31. Seacology funds community projects in Tingloy and Lobo, including tourism management and protection of a watershed that drains into the passage ¹⁵. Restoration teams in the VIP need to plan for strong currents, ship traffic and the risk of another spill, so sites with good water quality and active community management are the best places to start.

Open research questions

Spill aftermath. Published, reef-level surveys of coral and fish in the areas exposed to the 2023 Princess Empress spill are still scarce. Repeat surveys at fixed stations would show whether there were lasting effects ^16,17,19.
Mesophotic refuges. How much do the deep reefs off Puerto Galera and Batangas share species and larvae with shallow reefs, and can they help shallow reefs recover after bleaching ⁵?
Heat versus resilience. The regional station recorded its highest heat stress in 2020 and 2024 ¹¹. Which VIP reefs resisted, as Talim Bay's communities are expected to ¹³, and why?
Vents as natural experiments. Which corals at the Mabini vents tolerate low pH, and could they supply heat- or acid-tolerant stock for restoration ^22,23?
Network design. Can local MPAs in Batangas and Mindoro be coordinated into a systematically planned network across provincial lines, as Horigue et al. modelled ²⁴?
Industrial frontage. What are the cumulative effects of LNG terminals, power plants, dredging and ports on reefs in Batangas Bay ^20,26?

References

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Every source above was opened and checked when this page was written. Philippine university authorship is noted where it applies. Figures are quoted from the cited source and are not independently re-measured. This page is a research overview, not legal or management advice.

Verde Island Passage