Mo/m' 



20 



n ;h 



I 



I 



I • 



• ( «Mu 



•C \^ 



1 



^0 



Cmloropmylu in Mo/M* 



1 1. 



' 



Figure 8. Graph showing vertical distribution of chlorophyll as determined 

 by Kozminski's photometric studies of a number of Wisconsin lakes. C — 

 Crystal; H — Helmet; Ma — Mary; Mu — Muskellunge; Sc — Scaffold. The ordinate 

 represents depth in meters. The high chlorophyll-content of Scaffold Lake at 

 eight meters is caused by an abundant growth of Pelogloea bacillifera 

 Lauterbon. (From Kozminski, 1938.) 



sample is examined microscopically. The organism is easily mistaken 

 for a cluster of bacterial cells. In Scaffold Lake, Pelogloea bacillifera 

 was apparently the only organism responsible for the heavy absorp- 

 tion in Kozminski's photometric analyses. Phormidium mucicola was 

 the only other species found, and this was seen only after samples 

 of the lake water had been cultured in the laboratory. 



The rather curious flora of Scaffold Lake is accompanied by an 

 equally interesting chemistry. The pH is high in the upper levels 

 (pH 8.6-9.2) but drops to 6.3 at'nine meters. Bound carbon dioxide 

 is relatively low at the surface (5.0 ppm), but rises to 14.9 ppm at 

 the bottom. Free carbon dioxide is likewise low at the surface (3.0 

 ppm) but is plentiful at or near the bottom (4L0 ppm). Calcium is 

 present in 2.37-2.83 ppm. The color index is 26 (platinum cobalt 

 scale). These data make it possible to classify Scaffold Lake as a 

 medium hard water habitat, capable of supporting a luxuriant algal 

 flora; hence it could be said to have a high production potentiality. 

 An index to this is also to be found in Kozminski's chlorophyll analy- 

 ses. ( See also the remarks by Dutton, 1941, p. 397; Button and Man- 

 ning, 1941, p. 516; Manning and Juday, 1941, p. 363. ) 



In such a transparent lake as Crystal ( Wisconsin ) the chlorophyll 

 content is relatively low at all levels ( Fig. 8 ) , but shows a slight in- 

 crease near the bottom. This is in keeping with the prediction one 



[37] 



