162 



Information Storage and Neural Control 

 SURFACE 



DEPTH 10- 

 (ft) 



BOTTOM 



5 10 



MEAN COWMUNITY DIVERSITY 

 I bits X lO-yml ) 



Fig. 11. Mean community diversity, D = — ^ Nj log P(Si), at various depths. 



in which mean community diversity for the ten experiments, as 

 defined in Equation [4], is plotted against depth. The figure shows 

 maximum diversity at the 2 ft. leveL 



From the foregoing data (Figs. 4 and 11) it is concluded that 

 the living organisins of the York River summer plankton are 

 vertically stratified in excess of the extent attributable to cor- 

 responding heterogeneity of the physical environment (Fig. 3). 

 Maintenance of such a concentration gradient against the mixing 

 forces of the environment inust therefore be endergonic — the 

 organisms must expend biomass energy to reduce the entropy of 

 their distribution in space. 



