A team of researchers from the University of the Philippines Marine Science Institute (UP MSI) has uncovered a remarkable secret beneath the waves: Benham Bank, an underwater seamount off the Philippines’ eastern coast, harbors one of the richest deep coral ecosystems in the country. This discovery, detailed in a recent paper published in Coral Reefs, highlights the immense biodiversity thriving in this seemingly inhospitable location.
Located 50 meters below the surface, Benham Bank is taller than Mount Apo, the highest peak in the Philippines. The area, frequently battered by typhoons, surprisingly boasts pristine reefs. “Seamounts are known for high biodiversity and unique seafloor structures,” explained researcher Joey P. Cabasan. “They enhance ocean productivity and are considered biodiversity hotspots.”
The UP MSI study revealed an abundance of marine life. Researchers documented at least 11 genera of hard corals, with four sites exhibiting near-perfect (around 100%) coral cover. Ten genera of soft corals, at least four genera of macroalgae (seaweed), and arborescent sponges also thrived in this underwater haven. The overall mean hard coral cover across the 50-80 meter depth range was a remarkable 30%, significantly higher than other tropical mesophotic coral ecosystems (MCEs) found on isolated seamounts or closer to the Philippine mainland.
This remarkable resilience, according to Cabasan, is likely due to water stratification. “Benham Bank is resilient to physical and thermal stress,” he shared. “Stratification, or layers with different water properties, protects it from stress effects.” The upper 40-meter layer acts as a barrier, preventing mixing with lower layers.
Dr. Cesar Villanoy, a co-author, added another piece to the puzzle. “The water at Benham Bank is very clear,” he explained. “Low nutrient levels and chlorophyll, combined with light penetration to greater depths, allow corals and algae to flourish.”
The study identified eight probable habitat types within Benham Bank’s MCE, ranging from macroalgae-dominated to hard coral-dominated areas. This detailed classification is invaluable for policymakers, aiding in zoning the area for protection, fishing, and other uses.
Beyond its ecological significance, Benham Bank has considerable economic value. Traditional fishers from Infanta, Quezon, work the area, which the Philippine government designated as a protected food supply zone in 2017. Surveys have revealed over 60 reef-associated fish species, many commercially important, including snappers, groupers, and tuna. The bank also serves as a vital breeding and nursery ground.
Benham Bank’s strategic location further enhances its importance. “The area is affected by the North Equatorial Current,” said Cabasan, “potentially receiving larvae from other Pacific islands.” This current could facilitate coral reef recovery in other areas with poor coral cover.
Despite the challenges – a three-day boat journey and the need for meticulous planning to avoid monsoon season – the researchers believe their findings are crucial. Further research is needed, including studies on seasonal variations, fish communities, and connectivity to better understand the full ecological role of this remarkable seamount. With only 5% of the world’s seamounts currently protected, the preservation of Benham Bank’s pristine state is paramount. This requires immediate action to address both natural and man-made threats.
The UP MSI team’s research underscores the critical importance of Benham Bank, not only for the Philippines but for the global marine ecosystem. Its unique biodiversity serves as a powerful reminder of the urgent need for conservation efforts to protect these vital underwater habitats before it’s too late.
