particularly in those taken after 5 days„ We made no allowance 

 for orange colonies which possibly were not produced by F, pisci - 

 cidia since the counts were considered lovif even with the inclusion 

 of such colonies. An examination of the initial counts (Table 10) 

 obtained for the control containers (l and 2) and the two containers 

 receiving the smallest volumes of bacterial cultures (7 and 8) 

 suggests that counts of bacteria, exclusive of F, piscicida . 

 varied in the order of 0.3 to 0„8 million per ml. From these values 

 we presume that the actual concentration of Fo piscicida was approxi- 

 mately twice as great as the values listed. For example, the 

 initial number of F. piscicida in container 3 was probably about 

 4- million if one assumes that only about 1 million of the bacteria 

 per ml were other than F. piscicida . The initial counts of this 

 bacterium were in relatively good agreement with the various 

 dilutions employed. For example, the material in container 3, 

 which received the greatest volume of bacterial cultiire, yielded 

 a count of about 2 million chromogens per ml whereas the material 

 in container 8, which received only one-hundredth as much as 

 container 3, gave a count of 20,000 chromogens per ml. 



Since Bein gave only the ratio of F. piscicida culture and 

 sea water employed, the concentrations of bacteria used in his 

 studies cannot be directly compared with those we used. If the 

 amount of water discoloration is proportional to the abundance 

 of F. piscicida . we presume that the water in Bein's aquaria prob- 

 ably contained in excess £jf 4- million F. piscicida per ml at the 

 end of the 24--ho\ir experimental period. This presumption is based 

 on the observation that the sea water in container 3 of our experi- 

 ment was not appreciably discolored after the addition of 2 to 

 4- million £„ piscicida per ml, whereas in Bein's studies the 

 water was bright orange-yellow 24 hours after receiving the 

 bacterial cultures. 



GENERAL DISCnBSION 



The well-established association of Gymnodinium brevis with 

 the sporadic mass mortality of fish and other marine animals 

 occurring in the Gulf of Mexico since 1947, in conjunction with the 

 clear-cut laboratory demonstration that this dinoflagellate in pure 

 culture is toxic to fish, leaves no reasonable doubt that this organism 

 causes these mortalities. Considering this evidence, we propose the 

 name "brevis red tide" for such mortalities instead of the nonspecific 

 term "red tide" which is used commonly in popular and scientific 

 writing. In o\ir opinion there are ample characteristics to properly 

 identify these mass mortalities occurring in the Gulf of Mexico as 

 a distinct phenomenon. This phenomenon can be diagnosed by the 

 presence of G. brevis in the waters in which fish and other marine 

 animals are dying „ An additional diagnostic characteristic is the 



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