EFFECTS OF POWER-PLANT OPERATION 



605 



STATION 



3 

 1904 

 1907 

 1906 

 1118 



3 

 1904 

 1907 

 1906 

 1118 



57% TOTAL 

 (a) 



1904 

 1907 

 1906 

 1118 

 3 



19 

 19 

 19 

 19 

 19 



66% TOTAL 

 (b) 



Fig. 3 Comparison of differences in total phytoplankton density 

 during (a) nonstressed and (b) stressed (power plant in operation) 

 periods at adjacent stations. The small blocks at the left and right 

 indicate significant difference in counts. >, station to left greater; <, 

 station to right greater. Percentages are samples with no significant 

 difference (95% confidence limits for counts overlap). 



during a particular sampling (Lund, Kipling, and LeCren, 1958). 

 Results are summarized in Fig. 3. 



In the station comparisons for months without thermal stress, 

 57% exhibited no significant differences in density. Where there were 

 significant differences, the most frequent in all station comparisons 

 was a significantly greater density at station 1904 than at main lake 

 station 1907. All other station comparisons showed approximately 

 the same low number of samples with significantly greater or lesser 

 densities. 



In the station comparisons for the months with thermal stress, 

 66% exhibited no significant difference in density. Where there were 

 significant differences, the greatest were the number of times the 

 discharge station, 1904, showed higher densities than station 3, near 

 the intake, and the number of times 1907 densities were greater than 

 1906 densities. All station-pair relationships but one are in contrast 

 to those foimd for the nonstressed period. In both periods, station 3 



