SIZE-FRACTIONATED PRIMARY PRODUCTIVITY 365 



This study assesses the effect on the rate of phytoplankton 

 productivity of passage through the cooUng system at the Kewaunee 

 Nuclear Power Plant. An important facet of this research was the 

 determination of photosynthetic rates for three size classes of 

 phytoplankton, as well as for the total community. 



Passing through the cooling system of a steam electric-power 

 station subjects phytoplankton to a variety of stresses, including: 

 (1) mechanical stress from physical abrasion, pressure changes, and 

 turbulence; (2) thermal stress; and (3) chemical effects of antifouling 

 agents, corrosion products, and concentrations of dissolved gases 

 (Lauer, Walter, and Beck, 1972). The effects of these stresses are not 

 at all certain. The severity of a stress depends on its intensity and 

 duration and on the physiological condition of the organisms. 



The effects of temperature on microalgae were reviewed by 

 Hoogenhout £ind Amesz (1965). Patrick (1969) gave temperature 

 tolerance ranges for freshwater algae and stated that diatoms 

 preferred temperatures below 30°C and that condenser passage 

 causes little or no harm to algae if the temperature remains below 

 34.5°C. Furthermore, if the volume of the entrained water is small 

 relative to the volume of the receiving water body, any effect on the 

 phytoplankton population as a whole will likely be negligible 

 (Patrick, 1974). 



Many studies have shown that photosynthetic rates may be 

 affected by temperature changes and condenser passage. Warinner 

 and Brehmer (1966) showed that enhancement or suppression of 

 photosynthesis depends on initial temperature as well as the 

 temperature increase. Similar results were reported by other investi- 

 gators (e.g., Morgan and Stross, 1969; Brooks, 1972; Fox and Moyer, 

 1973). 



In a preoperational study at the Kewaunee Nuclear Power Plant, 

 Bremer and Redmond (1974) found that, in nine of ten sampling 

 periods, analyses detected a significant difference between the 

 precondenser and discharge productivity rates at Kewaunee. They 

 showed that mechanical effects could reduce productivity rates from 

 1 to 34%. Operational studies on immediate effects (7 hr after 

 sample collection) showed that chlorophyll was significantly lower in 

 the discharge on only one occasion (Jones, Brown, and Redmond, 

 1975). Significant difference in productivity between the precon- 

 denser and discharge sites was not detected. Furthermore, mechani- 

 cal effects were responsible for mean annual decreases of only 8% for 

 productivity and 5% for chlorophyll. Delayed effects (after 24 and 

 48 hr), although more variable, were still minimal. These studies 

 suggest that normal plant operations might have only limited effects 

 on phytoplankton assemblages entrained in the cooling water. 



