Date on Master's Thesis/Doctoral Dissertation


Document Type

Doctoral Dissertation

Degree Name

Ph. D.



Committee Chair

Wiedeman, Varley E.


Pesticides; Algae


Ten algal isolates were obtained from soil into axenic culture and placed into defined media containing from 0 to 50 ppm of DDT, 2, 4-D,2,4,5-T, rotenone, or malathion (in two purities, 95 and 99%). For nine of the isolates, growth was measured photometrically every two weeks for a period of two months. Because of the twisted growth form, of the tenth isolate, a visual estimation was used to measure its growth over the same period of time. The results of the experiments in the light were as follows: 1) 2,4-D and 2,4,5-T were generally neutral in their growth effects. However, both stimulated growth of two isolates, and 2,4,5-T inhibited the growth of two other isolates while 2,4-D inhibited only one. 2) Rotenone and DDT had mixed effects; rotenone inhibited five, stimulated three, and did not effect two isolates, while DDT inhibited four, stimulated one, and have no effect on five isolates. 3) Malathion was neutral toward one isolate and reduced the growth of all others. 4) In several cases, the isolates appeared to use the pesticides to supplement their growth. Two of the isolates were better able to withstand the effects of the pesticides and tended to be stimulated more often than the others. None of the algae were able to use any of the pesticides as a sole carbon source when grown in defined media in the dark for two months. Several isolates did not survive under those conditions, and none of the isolates survived in a 10 ppm DDT solution. The effect that pesticide use may have on natural populations of soil algae is discussed.