PRIMARY PRODUCTION 



531 



■10 



%OQ 

 <j 



S" 0(5 

 >. 



^ 04 



o 



*»- O 



5 /O /5 20 25 30 35 

 Zooplonkton (gOW) 



Fig. 5. The relations between the daily values of plants and zooplankton taken 

 from the two runs in Fig. 4. 



per unit of population. Thus for a growth rate of 50% the distance 

 between contours is 4.4 km whereas for 5% it is 44 km. As an 

 example of such distributions I reproduce in Fig. 6 two charts 

 from Cushing's (1955) study of production in the southern North 



Thalassiosira gravida 



Calanus. Stagei 



P lOO 200 30 OKm. 



Fig. 6. Examples of plankton patchiness (Gushing, 1955). 



Sea. The dominant diatom Thalassiosira gravida and the main 

 grazing component, Calanus, are shown contoured by factors of 

 about three. The division rate of the diatom is given as 40%, 

 which would mean a minimum distance between contours of 5.5 

 km. Along the southern edge of the patch where the zooplankton 

 are scarce, the distance is about 8 to 10 km. The zooplankton 

 patch, although it does not have such steep gradients, has about 



