EFFECTS OF POWER-PLANT OPERATION ON ZOOPLANKTON 



629 



60 — 

 50 

 40 

 30 

 20 

 10 

 



Interpolation 



8= 



..\, 



1 — I — I — r — r — r i i i i i 



1 — r-T* 



• Nauplii 



O Cyclopoid copepodids 



A Calanoid copepodids 



Ai AiAi A, 



r'^T'^T'^T^ \ 



JASONDJ FMAMJ JASONDJ FMAMJ JASONDJ FMAMJ J 

 1973 1 1974 1 1975 1 1976 



Fig. 5 Seasonal distribution of major zooplankton groups (Rotifera, 

 Copepoda, and Cladocera) from Belews Lake. Data plotted from 

 mean monthly euph otic-zone density, all stations. 



This inflated the year- 5 densities and accounted for the apparent 

 decline in year 6. Most of these taxa had a year-6 maximum. Note 

 that the spring peak of K. cochlearis was missed in year 5 (Fig. 6). 



The average density of Polyarthra spp. increased greatly in 

 postoperational years (Fig. 6). Comparisons between years, however, 

 showed a significant increase at only one station (1) in the year 6 to 

 year 4 comparison. Three stations in the year 5 to year 4 comparison 

 showed significant increases, while no significant differences were 



