When the Waters Turn Red

BY AWAKE! WRITER IN THE PHILIPPINES

Imagine fishermen walking down to the seashore, ready to carry out their early morning routine of preparing their boats and nets. As usual, they hope for a good catch of fish. But to their astonishment, a horrible sight meets their still sleepy eyes. Thousands of fish have washed ashore—dead. The cause of this mass destruction? A RED TIDE!

RED TIDES are a global phenomenon. They have been observed on both the Atlantic and the Pacific coasts of the United States and Canada. They have also occurred in Australia, Brunei, northwestern Europe, Japan, Malaysia, Papua New Guinea, the Philippines, and other places. Though relatively few people are aware of them, red tides are not new.

In the Philippines, a red tide was first seen in the province of Bataan in 1908. In 1983 a red tide poisoned fish and shellfish in the Samar Sea, Maqueda Bay, and Villareal Bay. Since then, red tides have been seen in many other coastal areas. Zenaida Abuso, of the Philippines’ National Red Tide Task Force, told Awake! that “besides the fish kills, the Bureau of Fisheries and Aquatic Resources of the Philippines has documented 1,926 cases of paralytic shellfish poisoning caused by red tides.” * But just what are these deadly phenomena?

What They Are

The term “red tide” applies to the discoloration of water that sometimes occurs in certain areas of the ocean or sea. Although the color is often red, it may also be shades of brown or yellow. The World Book Encyclopedia reports that “the discolored areas may range from less than a few square yards or meters to more than 1,000 square miles (2,600 square kilometers).”

What causes such discoloration? Red tides are generally caused by several species of microscopic, single-celled algae or by protozoans called dinoflagellates. These tiny organisms have hairlike projections called flagella—whiplike extensions, which they use to propel themselves in water. There are about 2,000 varieties of dinoflagellates, 30 of which carry poisonous substances. These minute organisms usually stay in warm waters with high salinity.

A red tide occurs when there is a sudden and rapid increase in, or bloom of, these microscopic dinoflagellates. The concentration of these organisms may swell to  50,000,000 per quart of water! Although scientists do not fully understand why this happens, it is known that dinoflagellates accumulate when certain conditions simultaneously affect the water. These include abnormal weather, optimum temperatures, an oversupply of nutrients in the water, a generous amount of sunlight, and favorable water currents. When a heavy rainfall occurs, minerals and other nutrients are sometimes washed from the land into coastal waters. These nutrients can contribute to the proliferation of dinoflagellates. The result? Red tides!

Sadly, it appears that humans sometimes exacerbate this phenomenon. When great amounts of industrial and human wastes are discharged into the water, the result can be an oversupply of certain nutrients. This can trigger the heavy population growth of dinoflagellates. Available oxygen in the water is soon depleted, resulting in large fish kills.

Red tides occur in warm seas and in calm coastal waters, usually between the end of warm months and the onset of the rainy season. They may last from a few hours to several months, depending on the prevailing conditions in the area.

The Victims

Most red tides are harmless; however, some are very damaging. Certain species of dinoflagellates release toxic substances into the water that paralyze and kill fish and other marine life. Some red tides have caused tremendous losses of fish, oysters, squid, clams, mussels, shrimps, and crabs that feed on the dinoflagellates. When a harmful red tide strikes, great numbers of dead fish may be seen floating in the water, and they may pile up on beaches for miles.

Humans have also been greatly affected. In areas where fishing is a source of income, red tides have deprived fishermen of their catch, which is their livelihood. Worse yet, red tides have caused the loss of human life.

Red-Tide Poisoning

One of the toxins released by some dinoflagellates is known as saxitoxin. This is a water-soluble salt that attacks the human nervous system. Thus, it is classified as a neurotoxin. The New Encyclopædia Britannica reports that “toxins released into the water are irritating to the human respiratory system.” Beach resorts have had to close  when red-tide toxins have been released into the air as a result of wave action.

Are you fond of eating shellfish and other seafood? Well, red tides can make shellfish that feed on the dinoflagellates poisonous. Infomapper magazine states that ‘bivalves and other shellfish like oysters, mussels, and clams pose the greatest danger because they are filter feeders and absorb more toxins than fish.’ However, “fish, squid, shrimps, and crabs . . . can still be safe for human consumption.” The reason? Red-tide toxins accumulate in the intestines of these creatures, and these are usually removed before cooking.

Still, there is need for caution when eating seafood—especially shellfish—taken from areas known to be contaminated by red tides. Such tides can cause a condition called paralytic shellfish poisoning, or PSP. If you have ingested red-tide toxins, you may feel symptoms within 30 minutes. The accompanying chart lists some of these symptoms. If not treated appropriately, PSP could culminate in respiratory paralysis, which can lead to death.

At present, an antidote for red-tide poisoning is still unknown. However, some emergency procedures have had a measure of success. Red-tide toxins may be removed from a patient’s stomach by inducing him to vomit. Gastric lavage through a stomach tube has also been used to expel the poisons. In some cases, artificial respiration is necessary. In the Philippines some feel that drinking coconut milk with brown sugar helps victims to recover faster.

The Solution

Presently, red tides are largely beyond our control. But many believe that the problem of red tides could be minimized if fewer chemical fertilizers and pesticides were used. This would prevent them from washing into the sea. Prohibiting the dumping of industrial and human wastes into bodies of water would also help. Another approach would be to rid coastlines of possible sources of nutrients that can cause the dinoflagellates to multiply.

In the meantime, some governments are carefully monitoring the situation. In the Philippines, for example, a government agency regularly tests shellfish to ensure their safety for local and international markets. Ultimately, however, only the Creator can eliminate the harmful effects that come to mankind when the waters turn red.

[Footnote]

[Box on page 24]

Symptoms of Red-Tide Poisoning

1. A tingling or burning sensation of the lips, gums, and tongue

2. Numbness and tingling of the face, which spreads elsewhere in the body

3. Headache and dizziness

4. An intense thirst and hypersalivation

5. Nausea, vomiting, and diarrhea

6. Difficulty in breathing, speaking, and swallowing

7. Joint aches and a feeling of lightness

8. Quickening of pulse

9. Muscle weakness and lack of balance

10. Paralysis of the body

[Pictures on page 24, 25]

Organisms responsible for red tides

Pyrodinium bahamense

Gymnodinium catenatum

Gambierdiscus toxicus

[Credit Lines]

Courtesy of Dr. Rhodora V. Azanza, University of the Philippines

Courtesy of Dr. Haruyoshi Takayama

ASEAN-Canada Cooperative Programme on Marine Science

[Picture on page 25]

Effects of red tide

[Credit Line]

Grant Pitcher/Courtesy WHOI

[Picture Credit Line on page 23]

Peter J. S. Franks, Scripps Institution of Oceanography

[Picture Credit Line on page 25]

Scripps Institution of Oceanography