By Henrylito D. Tacio
Contrary to common belief, red tides do not necessarily produce a red discoloration on the water.
“It may also reflect sunlight as a pink, yellow, orange, violet, blue, green and brown discoloration,” wrote Cesar E. Tordesillas in an article published in Health News some years back. “But since red is the most common pigment, the phenomenon came to be known as red tide.”
Dr. Rafael D. Guerrero III, former head of the Philippine Council for Marine and Aquatic Resources Development, says red tide is the discoloration of the sea caused by the sudden proliferation of plankton blooms. A main constituent of red tide is algae, a group of primitive plants dating to the first terrestrial life.
The microscopic killers in most cases are algae that occur in the form of dinoflagellates, tiny single-cell organisms that usually photosynthesize and contain chlorophyll but also have the animal-like trait of bearing twin tails, which whirl the organism forward.
According to Dr. Guerrero, dinoflagellates “can swim at the maximum rate of one meter per hour.” There are 2,000 types of dinoflagellates known to science, but only 20 species produce toxins or poisonous substances that kill human beings.
Tordesillas quoted Fe Bajarias, who was then the head of the red tide monitoring unit of the Bureau of Fisheries and Aquatic Resources, as saying that the first local red tide bloom in the country happened in 1908 at the Manila Bay.
“But the particular alga involved, peridinium, does not produce toxins harmful to the seafood eaters,” Tordesillas noted. “It only caused fish kill. But in June 1983, a red tide bloom consisting of the algae species Pyrodinium bahamense var. compressum invaded Masqueda and Villareal Bays in Western Samar, producing the first cases of red tide poisoning and fatalities in the country.”
But how the said red tide organism appeared in the country is still unknown. Some scientists believe the red-tide causing organism may have been introduced here through the ballast water of ships coming from other Pacific countries where the casual organism is endemic.
The Cavite-based International Institute of Rural Reconstruction (IIRR) says seeds (cysts) of Pyrodinium organisms are found at the muddy bottom of shallow coastal waters. They do not survive in fresh water.
“These seeds are resistant to harsh conditions and may remain viable for one million years,” the Ramon Magsaysay awardee institution says. “Under favorable conditions, the seeds can germinate into a free-floating form suspended in seawater.”
Favorable conditions include right temperature and amount of nutrients. “During the day, the seeds are found near the surface where they receive sunlight for their photosynthesis activities,” the institute says. “At night, they occur deeper in the water column where they receive nourishment.”
The organism multiplies asexually and rapidly during its productive stage, which results in bloom. During dormancy, the organism reproduces sexually and form cysts that “hibernate” in the sediment until activated by favorable conditions.
Some marine scientists believe that red tide outbreaks are linked to pollution. Take the case of Manila Bay. Monitoring in 1994 by the Environmental Management Bureau of the Department of Environment and Natural Resources showed that some parts of the bay were “not fit for food production.” No wonder, the red tide keeps coming back in the bay.
Unusual weather, too, contributes to the proliferation of the red tide organisms. Dr. Howard Seliger, author of Biology, Epidemiology and Management of Pyrodinium Red Tide, cites the outbreak in 1972, where a different red tide organism was distributed to the Gulf of Maine and southeast Florida in the United States.
The toxic red tide organism also appeared in Papua New Guinea that very same year. In 1976, it was reported in Brunei and Sabah in Malaysia. In 1983, it appeared in the Philippines. “All these were years of unusual weather conditions caused by El Niño,” wrote Seliger.
El Niño, Spanish for “the child,” is a warm ocean current that appears every three to six years in the eastern Pacific Ocean and affects climate and current patterns over a wide area of the globe.
Dinoflagellates serve as food to shellfish and other marine bivalves. When shellfish ingest too much of these, the shellfish become contaminated with red tide poison proven to be deadly to human beings. The most common shellfishes infested by red tide are mussels, oysters, scallops, cockles and limpets.
Experts claim fish and other seafoods such as squids, shrimp, crabs, lobsters, and seaweeds are generally safe to eat even when caught from red tide-infested provided they are washed thoroughly and the internal organs removed.
Dr. Guerrero says people get poisoned even if the contaminated shellfish is cooked because the toxin is not destroyed by heat. The poison in the red tide organism is known as saxitoxin. It is a water soluble salt that affects the nervous system. The potency of saxitoxin has been reported to increase by acidic chemicals like vinegar used in preparing common Filipino dishes such as adobo and paksiw, and the hydrochloric acid present in the human stomach.
In medical parlance, red tide poisoning is called paralytic shellfish poisoning. “Its symptoms appear 30 minutes after eating the contaminated shellfish, and are a numbness and tingling sensation around the lips, tongue, mouth, face and jaw. Headache, dizziness and nausea follow,” Bajarias informed. These symptoms may be mistaken for drunkenness and may be aggravated by alcohol consumption.
“In severe cases, it would later progress to paresthesia (muscular paralysis) of extremities with a feeling of lightness, numbness and/or periorbital edema (swelling around the eyes), difficulty of movement and breathing,” Bajarias further explains. “Finally, there would be respiratory failure that causes the eventual death of the victim. Death generally occurs within 17 hours after the onset of the symptoms.”
Doctors say the first thing to do in a poisoning case is to empty the victim’s stomach by giving the victim an oral emetic or simply by inserting a finger into the throat to induce vomiting. Since the toxin dissolves in water, the victim may also be given plenty of water to induce urination and minimize gastrointestinal absorption of the toxin.
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