in 96 hours. The decrease of Aroclor 1254 can probably be attributed 

 to volatilization and, to a lesser extent, by uptake of organisms and 

 absorption to the glass walls of exposure containers. Such phenomena 

 create difficulties in toxicity analysis since organisms are not exposed 

 to a constant level of toxicant throughout the experiment. The initial 

 exposure concentration has been used in expressing the toxicity of 

 Aroclor 1254 to Palaemonetes pugio. Although such a practice does 

 not completely describe the experimental situation, relative toxicities 

 to organisms under similar conditions would not be altered. In the 

 larval experiment, concentrations fluctuated in 2-day cycles since ex- 

 posure media were renewed every second day. 



Ninety-six hour LC50 values for adult shrimp are presented in Table 

 11 A. Since the presence of 200 mg/liter acetone did not decrease the 

 96h LC50 of the "partially equilibrated" seawater. it was concluded 

 that synergism by acetone and Aroclor 1254 did not occur. The 

 slightly lower 96h LCo of 41 ug/liter for shrimp exposed to Aroclor 

 1254 dissolved in acetone may have resulted from the PCBs occurring 

 in a more finely dispersed state due to the activity of the solvent car- 

 rier. 



Juvenile shrimp with 96h LC50 values from 6.1 to 7.8 ug/liter 

 (Table 11) were more sensitive than adults. Values were slightly 

 lower at the lower salinities, but the magnitude of the difference was 



Table 1 1 



Toxicity of Aroclor 1254 to Adult and Juvenile Palaemonetes pugio: 



96h LC,g Values. 



A. Adults gehLCjo 



Test Solution (ug/liter) 



Aroclor 1254 equilibrated directly with 15%o seawater 64 

 Aroclor 1254 equilibrated with seawater (5 liters) plus 



1 ml acetone (=200 mg/liter acetone) 86 



Aroclor 1254 dissolved in acetone 41 



B. Juveniles 96h LCgg 



Salinity (%o S) . (ug/liter) 



1 6^^ 



7 6.1 



14 7.8 



21 7.8 



28 7.8 



35 7.8 



38 



