398 



R. J. Barsdateet al. 



5.0 



4.0 



^3.0 



20 



FIGURE 9-7. Primary production in 

 subponds after various treatments. 

 (After Federle et al. 1979.) 



The quantity of phytoplankton, measured by direct counting with an 

 inverted microscope, changed only a little as a result of the oil spill in Pond 

 E on 16 July 1970 (Figure 9-5). Within 3 weeks of the spill, the amount of 

 algae did double but a similar pattern was seen the following summer. This 

 may be an advancement of the late summer bloom that had been released 

 by removal of the zooplankton. A similar increase, measured as 

 particulate carbon, occurred after the oil addition in the Mackenzie Delta 

 lakes (Snow and Rosenberg 1975b). 



The long-term primary productivity of the phytoplankton was not 

 changed appreciably by the oil spills (Figure 9-6). There is enough 

 variability from pond to pond and year to year that the differences 

 between Pond E and Pond C (the control) cannot be attributed to the oil. 

 However, the productivity of Pond E certainly was not lessened by the oil 

 except during the first summer. The same effect, a temporary reduction in 

 primary production, was seen after the 1975 oil spill in Pond Omega 

 (Figure 9-6). 



The reduction in primary productivity is directly proportional to the 

 amount of oil added. Federle et al. (1979) found that when various 



