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Vol. XXVI, 4th Quarter
October – December 2008


Clay can curb red tide

THE ADAPTABLE CLAY can restrict the mess that the dreaded “Red Tide” inflicts when it’s in deadly cycle. These tiny monsters are blooms of certain marine organisms in coastal waters like the dinoflagellate Pyrodinium bahamense var. compressum, which can “intoxify” mussels that filter them from the water.

Dr. Rhodora Azanza and a group of researchers at the University of the Philippines’ Marine Science Institute have tested a technique developed by South Korean counterparts using a ball of clay to control Pyrodinium bahamense var. compressum in the laboratory. They found that at 0.5 gram of clay per liter of water, the population of the organism suspended in the water went down from 95% to 51%.

In South Korea, researchers at the National Fisheries Research and Development Institute previously found that application of 8 grams of clay per liter of water in red tide-stricken waters effectively reduces by 80% the populations of the dinoflagellate Cochlodinium yolykrikoides. This type of red tide can cause fish kills at high densities, PCAMRD reported.

The clay particles flocculate or band the suspended organisms together in the water and settle them at the sea bottom where it becomes inactive. No


red tide

significant negative effects on water quality and marine life have been reported.

Since 1983, Red Tide episodes have occurred in the country in Maqueda Bay, Samar. The Bureau of Fisheries and Aquatic Resources, an attached agency of the Department of Agriculture, monitors the deadly blooms in 27 sites.

When consumed, red tide can lead to death. So far, no mitigating measures have been put into operation in the past, the Philippine Council for Aquatic and Marine Research and Development of the Department of Science and Technology has noted.