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There are unique reef habitats surviving in Manila Bay, scientists say

There is more life in Manila Bay than we might think.

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Photos courtesy of the Aquatic Zoology Research Lab, UP Los Baños

There is a picture of Manila Bay in our minds—black water, floating garbage, the stench of human waste mixed with salty air—that makes it difficult for us to understand how it could ever sustain life. But according to reef ecologist Dr. Victor Ticzon of the University of the Philippines Los Baños, one of the scientists that helped formulate the Manila Bay Sustainable Development Master Plan, the bay is actually more alive than we think.

“We have this misconception na madumi [ang Manila Bay], but actually sa may Mariveles, Corregidor, and Carballo Island, there are thriving underwater communities,” he says.

Found in the western side of Luzon, Manila Bay is more than the body of water we see on sunset strolls along Roxas Boulevard; its coastline actually spans 190 km long, and runs through the provinces of Cavite, Metro Manila, Bulacan, Pampanga, and Bataan.

In March 2020, Victor and his team conducted a survey on the different ecological habitats in Manila Bay and found living coral reef ecosystems in Cavite, Bataan, and Corregidor Island. They also learned that the coral ecosystems in Corregidor and Carballo Island are thriving greatly, so much that it’s even surpassed the national and regional averages for hard coral cover in the Indo-Pacific.

“The Indo-Pacific average for hard coral cover is estimated at 22 percent, while the national average is slightly higher at 22.8 percent. Corregidor and Carballo Islands are estimated to have hard coral cover that is higher than both national and regional averages, so… it also warrants our attention,” he says.

A member of the giant clam family (Family Cardiidae, Sub-Family Tridacninae) found in the shallow reef flat of Carballo Island.

The current can also be strong in these parts of the bay, so the coral types that grow here are hardier than most. These include massive and encrusting corals that are both resistant to the pounding of waves.

According to Victor, each hard bottom habitat surveyed was physically and biologically unique, featuring distinct assemblages of corals and other benthic organisms that contribute to biodiversity enhancement.

“[Conservatively], coral reefs in Manila Bay comprise less than two percent of the entire Manila Bay area,” he says. Because Manila Bay is a natural estuary—a place where large volumes of freshwater meets seawater—areas where corals can grow are limited to the mouth of the bay. “Corals have limited area to colonize and grow compared to mangroves, mud flats… so it adds value to the reefs in the bay. Konti nalang sila kaya mas mahalagang protektahan din natin sila.”  

Mangroves help filter out nutrients and sediments that can negatively impact corals, making them a key ecosystem in Manila Bay.

Two of the biggest threats facing corals are sedimentation and nutrient influx, which result from improper watershed management. Sand and silt suffocate and abrade corals, while nutrients encourage the growth of algae that compete with corals for space.

Reports about the existence of coral reefs in Manila Bay have been around for some time now, albeit the research is still a bit thin. In 2019, a report by the Department of Environment and Natural Resources’ Ecosystems Research and Development Bureau (DENR-ERDB) also showed that coral gardens were blossoming in areas off the coast of Cavite and Bataan.  

“Overall we were only able to sample an area less than 1000 sq.m., so it’s really just a glimpse of the big picture,” he adds.

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