7. What causes the red tide? 



The red tide and its effects on fish have been known since Biblical 

 times. Dr. Harris B. Stewart, Jr., Director of the Institute for Oceanog- 

 raphy of the Environnnental Science Services Administration, says that 

 probably this particular phenomenon had occurred in the lower Nile 

 and is recorded in the Bible in the seventh chapter of Exodus ". . . .and 

 all the waters that were in the river were turned to blood, and the fish 

 that were in the river died; and the river stank, and the Egyptians could 

 not drink the waters of the river." 



A red tide, with its mass fish kill, occurs when the following two con- 

 ditions exist: (1) physical factors are favorable to the rapid reproduc- 

 tion of dinoflagellates (Gymnodinium), and (2) the number of predators 

 is temporarily reduced. Dinoflagellates are one-celled organisms with 

 characteristics of both plants and animals. Although less than a thou- 

 sandth of an inch in size, they reproduce so rapidly that a quart of sea 

 water may contain 100 million. 



Millionsof fish may be killed during such a plankton "bloom." More 

 than 50 million were reported killed off Florida in 1947. 



Deacon, Go E, R. (Ed.) 



Seas, Maps, and Men, Doubleday and Company, 1962. 

 Stewart, Harris B., Jr. 



Deep Challenge, Van Nostrand, 1966. 

 Troebst, Cord-Christian 



Conquest of the Sea, Harper and Row, 1962. 



