530 



CYCLES OF ORGANIC AND INORGANIC SUBSTANCES 



S02 

 o 



■§-0/1 



72 

 ■/O 



08:g 



06 



04 'H 



02^ 



5 10 15 20 25 JO J5 40 



5/0/5 20 25 JO J5 40 



5 /O /5 20 25 JO J5 40 

 Days 



Fig. 4. The effects of random zooplankton \ariations (Z) on the plants (P), 

 and on phosphate-phosphorus, as deri\ed from the theoretical model. 



balances the effects of diffusion. Thus, on this basis, for a growing 

 patch, the gradients must be less steep than this limiting value. 

 The gradients are expressed in exponential form so that the plant 

 concentrations increase by a multiplicative factor over equal dis- 

 tances. For a factor of three, which is often used in drawing con- 

 tours, the limiting relation is that the distance in kilometers 

 between such contours equals 2.2 divided by the production rate 



