such as toluene — a prime constituent of treated oil tanker ballast 

 water. Yeast populations were fairly insensitive to submillimolar 

 levels, showing only a slight stimulation in leakage of internal 

 cellular constituents. Algae populations, on the other hand, 

 were sensitive to toluene levels as low as 50 micromolar. 



Crude oils, either as water-solubles or as whole oils, did not 

 prove very inhibitory to algal growth. However, water-solubles 

 from fuel oils can be quite lethal to microalgae depending upon 

 the sample and the algae used as test organisms. Figure 8 shows 

 that two compounds identified in the water-solubles, p-toluidine 



and phenalen-l-one, were highly toxic to a blue-green and a 

 green alga, respectively. The other three compounds were much 

 less toxic, and the algal response was more uniform. Whole fuel 

 oils added directly to the algal culture medium were also toxic. 

 Again, toxicity varied with the fuel oil sample and the test 

 organism. The compounds responsible for the toxicity of whole 

 fuel oils have not yet been identified; however, they should be 

 different from and of a more lipophilic nature than the com- 

 pounds in the water-soluble fractions. Water-soluble extracts of 

 No. 2 fuel oil are lethal to benthic crustaceans at 4 ppm for 



MOST 



COMPOUND 



AMOUNT ON 

 PAD, MG 



SENSITIVITY 



LEAST S 



♦most 



TOXICITY 



NH 9 



0.001 



CH 3 



p-toluidine 



0.01 



phenalen-l-one 



H3C CH- 



0.5 



2 , 5-dimethylpyrole 



ir* 



1.0 



h 3 c 



2 , 5-dimethylphenol 

 CH 3 



:h 3 



10.0 

 ch 3 



1,2,3,4- 

 tetramethylbenzene 



(1) (2) 

 Gj D 



(3) 

 B 



D, B 



D, B, G 



G D 



B 



D, B, G 



LEAST 



1) Green alga, Chlorella autotrophica , strain 580 



2) Diatom, Cylindrotheca sp. , strain N-l 



3) Blue-green alga, Agmenellum quadruplicatum , strain PR6 



Figure 8. — Algal lawn assay of pure compounds for toxicity. 



11 



