0.1 



0.4 



0.5 



0.2 0.3 



Exposure time, hours 



Figure 7. Mean survival of Creseis acicula vs concentrations of water soluble 

 fractions of No. 2 fuel oil for various exposure times. Compare Figure 6. 



data are limited, restricted as they are to one species, whereas it is 

 to be expected that species differences will exist in this regard. 



Trace Metals 



The biological effect of heavy metals was studied by the Texas A&M 



36 



