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WELCH AND WARD 



200 



150 



I 100 



O 

 ca 

 az 

 < 



50 



V b & 



Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug. 



MONTH 



Fig. 2 Seasonal variation of the surface-water primary produc- 

 tivity. 



Biological Measurements 



On the basis of aneilysis of variaiice techniques, primary 

 productivity was significantly higher at the discharge station on 18 of 

 26 samphng dates (Fig.2). On five samphng dates there were no 

 significant differences between stations in the amount of carbon 

 fixed. On three sampling dates productivity was significantly higher 

 at the unheated station. There was no apparent relationship between 

 higher productivity and biomass or community composition between 

 the two stations. At all times, dark-bottle fixation was ~10% of 

 light-bottle fixation at both stations. 



The difference between the two stations in the amount of carbon 

 fixed could be considered the difference in photosynthesis (AP). 

 There was no correlation between the difference in temperature, AT, 

 and the difference in carbon fixation, AP. 



Analysis of variance showed nutrient enrichment had no effect 

 on primary productivity in any of the experiments. Experiments 

 incubating hot-water samples at the ambient station and ambient- 

 water samples at the heated station showed statistically significant 

 effects of temperature in five of eight experiments (Fig. 3). Ambient- 

 water samples incubated at increased temperatures showed increased 

 productivity rates, and, conversely, samples from the discharge 



