Table 2.— Results of six toxicity tests in terms of percentage mortality of G. breve after 2.', hours exposure 



Chemical 



Carh;miic acid, dicllivlililliio-: Ipllurium salt — 



Curhamic aid. diimthyWitliio-; ferric salt 



Disulfide. bis(diet hyUliioearbamyl) 



Sulndo. bi5r2-hydroxy-.'Miromo-.Vclilon)i)llenyl)-; 



bis dimithvlaniinn butyne mono salt 



Sulfide. ois(2-bydroxy-:i-broino-5-chloroplieiiyl)- 



cycloiictylamiiic mono salt - -- 



Tost numbers for concentration 

 of 0.01 p. p.m. 



100 

 10(1 

 100 



25 



25 



100 

 100 

 100 



100 



.■so 



100 

 75 

 75 



50 



25 



100 

 100 

 100 



100 



100 



100 

 100 

 100 



75 



100 



100 

 25 

 



25 







Test numbers for concentrations 

 ofO.OOli p.p.m. 



The selective chemicals were tested to determine 

 their minimum toxic concentration levels to G. 

 breve. Each toxicant was tested six times at 0.01 

 and 0.003 p.p.m. The results, in terms of mortality 

 of G. breve, apjicar in table 2. Variation was con- 

 siderable among the supposedly replicate sets of four 

 of the chemicals. This suggests that the concentra- 

 tion of the.se four chemicals was close to the toxic 

 threshokl. At or close to the toxic threshold level, a 

 slight variation in the concentration of a toxicant 

 can have a pronounced effect on the mortality of 

 organisms in cultures containing the toxicant. 



Only one of the selective toxicants, carbamic acid, 

 diethyldithio-; tellurium salt, consistently met the 

 toxic requirement arbitrarily established for a con- 

 trol agent (R. T. Vanderbilt Co., Inc., 230 Park 

 Avenue, Xew York City, N.Y. 10017; $2.13 per 

 pound in 100-pound containers). This compound 

 has two shortcomings, however: it killed 10 jiercent 



of the test organisms of two species (table 1); and 

 its cost is proliiliitive for massive u.se in the field. 



LITERATURE CITED 



Feinstein, A.nit.\, a. Russei, Ceuuvels, HonEiiT F. 

 lIcTTON, and Edw.^rd Snoek. 



1955. Red tide outbreak.s oft the Florida west eoa.^t. 

 Univ. Miami, Mar. Lab., Rep. 55-15 to Fla. State Bd. 

 Conserv., 44 pp. 

 M.\nviN, Ke.nxeth T., L.vnENcE M. L.\nsford, and R.\y S. 

 Wheeler. 



1961. lOffects of copper ore on the ecology of a lagoon. 

 I'.S. Fish Wildl. Serv., Fish. liull. 61: 15:5-100. 

 Marvin, Ke.\neth T., and Raphaei, R. Proctor, Jr. 



1964. Preliminary results of the systematic screening 

 of 4,306 compounds as "red-tide" toxicants. U.S. 

 Fish Wildl. Serv., Data Rep. 2, 3 microfiches CU- 

 SS pp.). 

 Rou.NsEFELL, Geor<;e .\., and Joii.\ E. Evans. 



1958. Large-scale experimental test of copper sulfate 

 as a control for the Florida red tide. U.S. Fish Wildl. 

 Serv., Spec. Sci. Rep. Fish. 270, vi-l-57 \)\i. 



164 



U.S. FISH AND WILDLIFE SERVICE 



li- U S. GOVERNMENT PRINTrNG OFFICE: 1967—0 219-992 



