250 



WETZEL AND RICH 



TABLE 2 



RELEASE OF DISSOLVED ORGANIC CARBON BY 

 PRIMARY PRODUCERS, LAWRENCE LAKE, MICH. 



TABLE 3 



DISSOLVED ORGANIC CARBON, 

 LAWRENCE LAKE, MICH. 



Mean g C m 



Mean kg C lake ' 



Average 



30.23 



1502 



Available evidence indicates that, in general, the percentage of photosyn- 

 thetically fixed carbon secreted as DOC is greater in less fertile aquatic systems 

 than in those more highly fertile. Since quantitative primary production is less in 

 more oligotrophic waters, however, the absolute amount of DOC secreted is 

 greater in more eutrophic lakes. 



