Information Concept in Ecology 



153 



oxygen diminished only slightly with depth, and dissolved phos- 

 phorus and nitrate increased slightly (Fig. 3). 



In sharp contrast to these physical relationships, the living 

 organisms of the phytoplankton were markedly stratified in the 

 upper layers (Fig. 4). To account for this we note that the domi- 

 nant organisms of the summer flora were motile flagellates closely 

 related to forms which are known to be positively phototactic. 

 Thus, swimming is the probable primary mechanism involved. 

 Other factors of possible influence include rapid cell division in 

 the lighted surface layers, and manufacture of low specific gravity 

 (lipid) storage products. 



The mean daily vertical distribution of light in the ten experi- 

 ments is graphed in Figure 5, and shows typical exponential 

 extinction with virtually complete absence of light at the bottom. 



SURFACE 



DEPTH 

 (ft) 



10 - 



MEAN EXTINCTION 



COEFFICIENT = 0.97 



BOTTOM 



I I I I 



200 400 600 



MEAN SUBMARINE ILLUMINATION 

 ( gcal cm-2day-' ) 

 Fig. 5. Mean vertical distribution of light in the ten experiments. 



