•Fish 



• Zooplankton 



•Bottom fauna 

 •Bottom flora 



Phytoplankton 



Dissolved organic 

 matter 



Figure 3. Relative weights of various components of the biota and dissolved 

 organic matter in Weber Lake, Wisconsin, a soft water seepage type. Scale: 

 4.9 sq. mm. = 1 kilogram per hectare. (From Juday, 1943) 



than hard water, eutrophic habitats. In their studies Henrici and 

 McCoy ( I.e. ) show that the bacterial flora of the bottom is larger 

 in numbers of individuals than that of open water and that, as might 

 be expected, the difference between the bottom and upper level 

 flora is greater in eutrophic than in oligotrophic lakes. 



In ohgotrophic Crystal Lake, Vilas County, Wisconsin, for ex- 

 ample, the bacteria count per cc. of bottom mud sampled was 2,160; 

 whereas in Alexander, a eutrophic lake in Minnesota, the count was 

 144,240 per cc. of bottom "kalkgyttja." In the former lake the total 

 bacterial flora of the bottom ( average bacteria per cc. x depth of the 

 mud) was 38,880 as compared with 2,599,320 in Alexander Lake. 



In the examination of the open water of the two lakes, an inter- 

 esting bacterial count was secured. In Crystal Lake the average was 

 80 organisms per cc; in Alexander, 675 per cc. When the ratio of the 

 number of bottom bacteria to open water bacteria in the two lakes is 

 compared, an even greater difference is noted. In Crystal Lake the 

 total open water flora (average bacteria per cc. x depth of the lake) 

 is 159,900, which, when compared with 38,880 on the bottom, gives a 

 quotient of 0.2. A much higher ratio is found in the eutrophic type 

 of lake. In Alexander there was a total of 538,300 organisms in the 



[24] 



