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(1978) 



Figure 6. --Monthly means of daily solar radiation, 



production (figs. 3, 4, and 5). If any other environmental factor was 

 limiting, the rate of oxygen production would level off, indicating light 

 saturation. In contrast to our field measurements, most studies using enclosures, 

 even with stirring, commonly report light saturation. This is likely an artifact 

 of insufficient water motion. In more recent work with chambers (e.g., Carpenter, 

 in ms.), where efforts have been made to simulate surge motion, this lack of 

 light saturation for algal turfs is repeatedly demonstrated. 



In this investigation, daily solar radiation levels were recorded with a 

 pyrohel iometer (see fig. 6 for monthly mean values). During our study we 

 sampled two periods of high light intensity (May and August) and two periods of 

 lower light intensity (January and October). Averaging hourly production rates 



180 



