EFFECTS OF POWER-PLANT OPERATION 599 



waters warmed by thermal power-plant effluents (Pannel, Johnson, 

 and Raymont, 1962; Hockley, 1963; Morgan and Stross, 1969; 

 Foerster, Trainor, and Buck, 1974). 



The objectives of this study were to focus on the phytoplankton 

 community and to determine cyclical and successional changes in 

 response to the evolving aquatic environment and the added thermal 

 stress. The 4-year study (July 1972 to June 1976) encompassed two 

 preoperational and two postoperational years. 



MATERIALS AIMD METHODS 



Three sampling stations were located on the discharge arm of the 

 lake, four on the upper main lake arm connected to the discharge 

 arm by a canal, two on the intake arm, and two in the lower lake 

 near the dam (Fig. 1). Data were collected monthly for a complete 

 year from five stations in year 3, ten in year 4, eleven in year 5, and 

 eight in year 6. Four stations were studied through all 4 years, and 

 eight stations were examined for the complete 3-year period after 

 establishment of full-pool level. 



A wide spectrum of water-quality parameters were measured to 

 characterize the physical and chemical environment of the lake. 

 Those referred to in this paper include (1) temperature, measured 

 with a multiprobe surveyor, (2) water transparency, measured with a 

 Secchi disk, (3) soluble reactive phosphorus, measured by the 

 automated stannous chloride method (Environmental Protection 

 Agency, 1974) with an autoanalyzer, and (4) inorganic nitrogen 

 (NO2— NO3— NH3— N), also measured with an autoanalyzer after 

 procedures similar to Environmental Protection Agency methods. 



For the phytoplankton investigation, monthly water samples 

 were drawn from the Secchi depth, except in year 6, when composite 

 samples representing the euphotic zone were constituted. Because 

 there is presently no known fixative that can adequately preserve all 

 classes of phytoplankton without disturbing their morphology or 

 pigmentation (Reynolds, 1973), live samples were collected for 

 examination to ensure accurate identification and classification. 

 Samples were kept on ice without preservation and returned to the 

 laboratory for prompt study. 



Samples were concentrated by centrifugation and examined live. 

 After a 10-ml aliquot was centrifuged and the centrifugate drawn off, 

 the final 0.5 ml containing the concentrated algae was mixed and 

 transferred to a microscope slide, where the drop was spread, by 

 adding a cover slip, to the exact area of the cover sUp. The edges 

 were ringed with a paraffin— petroleum jelly mixture to prevent 



