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Image Source: philippine-resources.com

BONGABON, Nueva Ecija — Government should make a scientific assessment of the fish population at the 13-million hectare Benham Rise maritime area because it may be premature to claim that it teems with marine resources.

Aquaculturist Virgilio “Gil” Marzo said that the extinct volcanic ridge, which rises two kilometers (km) from the five-kilometer seabed and has a diameter of 250 kilometers, may appropriately be called as a maritime highway through which pelagic fish species pass.

It is composed mainly of basalt, an igneous rock, and theoretically, it may not harbor underwater vents that also sustain some forms of fish and crustaceans in deeper sections of the Pacific Ocean.

“Since the vast area is still three kilometers below sea level, no schools of fish stay there. Various fish species pass through Benham Rise to look for food,” Marzo said.

Trained at the University of the Philippines College of Fisheries (UPCF) as well as in Taiwan and Saudi Arabia, Marzo said the highest point of the landform is only between 35 meters and 40 meters from the sea surface and is located near the Benham Seamount.

This elevation is not suitable for the survival of giant clams or “taklobo” that flourish in Palawan reefs, Marzo said, because sunlight has to reach 20 meters below the sea surface for the survival of plants and other organisms that nourish these clams.

“If there are no phytoplanktons in the area, there would be no forage fish like sardines and the pelagic fish population would necessarily be low,” Marzo also said.

Writing for Ocean Explorer of the National Oceanic and Atmospheric Administration (NOAA) of the US, Dr. Steve Gaines of the University of California at  Santa Barbara (UCSB) and Dr. Satie Airame, science advisor of the Channel Islands National Marine Sanctuary, said that winds also play a part in creating currents that distribute of phytoplankton and sea animals through upwelling.

“Winds powerfully affect the oceans and are an important force in creating currents. From global circulation of entire oceans to microscopic patterns of turbulence, winds move water and its resident animals and plants in complex and interesting patterns. When the wind blows parallel to the coastline, an intriguing and biologically important event occurs.

“Affected by the rotation of the earth, winds can move water at right angles to the direction the wind is blowing, a phenomenon known as the Coriolis effect… winds that blow from the north tend to drive ocean surface currents to the right of the wind direction, thus pushing surface waters offshore. As surface waters are pushed offshore, water is drawn from below to replace them. The upward movement of this deep, colder water is called upwelling,” they said.

“The ecological effects of upwelling are quite diverse, but two impacts are especially noteworthy. First, upwelling brings up cold, nutrient-rich waters to the surface, which encourage seaweed growth and support blooms of phytoplankton. The phytoplankton blooms form the ultimate energy base for large animal populations higher in the food chain, including fish, marine mammals and seabirds… Although coastal upwelling regions account for only one percent of the ocean surface, they contribute roughly 50 percent of the world’s fisheries landings,” Gaines and Gairame said.

“The second major consequence of upwelling involves its effect on animal movement. Most marine fish and invertebrates produce microscopic larvae as young which drift in the water as they develop. Depending on the species, they may drift in ocean currents for weeks to months. For adult marine creatures that live in shallow waters near shore, upwelling that moves surface water offshore can potentially move drifting larvae long distances away from their natural habitat, thus reducing their chances of survival. Therefore, upwelling can be a mixed blessing to coastal ecosystems. It can infuse coastal waters with critical nutrients that fuel dramatic productivity, but it can also rob coastal ecosystems of offspring required to replenish coastal populations,” they added.

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