Captive Red Tide

When the waters off Florida's west coast were infested by the dreaded "red tide" nine years ago, fish died by the million and lay in" stinking windrows on the beaches. The spray of the poisoned surf inflamed human throats and lungs. Tourists deserted the hotels, schools were closed, beach areas evacuated. Although scientists knew that the tide was caused by poisonous microorganisms called dinoflagellates, nobody knew what made the organisms bloom so suddenly.

Researchers in Manhattan's Haskins Laboratories now think they have the answer. When Microbiologists Luigi Provasoli and S. H. Hutner started their research, they knew that red tides seemed to occur soon after heavy rains had fallen over the land. Near the mouths of rivers the runoff reduced the saltiness of the ocean and supplied it with vitamin B12, manufactured by soil microorganisms, and with phosphorus from phosphate rocks. With this data as a starter, Provasoli and Hutner, helped by Graduate Student J.J.A. McLaughlin. concocted a synthetic sea water containing everything that dinoflagellates need. The successful prescription calls for many salts and trace elements, e.g., zinc, manganese, molybdenum, as well as a collection of vitamins.

By last week they had cultivated 15 species of dinoflagellates and some new facts. Always present in sea water, the dinoflagellates multiply rapidly as the sea's concentration of phosphate and vitamin B-12 increases. The toxin that they secrete kills a few especially susceptible fish. Bacteria attack the dead fish, liberating more nutrients and vitamins and making the dinoflagellates multiply even faster. Soon a biological chain reaction is sweeping through the water.

The dinoflagellates' toxin is probably the most powerful poison known, say the microbiologists. It blocks the nerves, causing paralysis in somewhat the same way as curare, the South American arrow poison. Since curare has important medical uses, Drs. Provasoli and Hutner hope the dinoflagellate toxin may prove useful too.

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