ISAACS: FOOD WEBS AND "POLLUTANT ANALOGUES" 



These expressions can be employed to gen- 

 erate expressions for the coefficient R, or the 

 increase in the concentration of any component 

 passing through the food web and introduced 

 only via plants. The derivation follows that of 

 equation (11) above, where j is the coefficient 

 of increase over the conversion of food, as in 



equation (8) above, where j ^ 3. Also, for in- 

 terest, is shown the coefficient N, which is the 

 Jimiting or maximum increase in the biomass 

 of each trophic type resulting from a unit input 

 into the food web (i.e. Mo = 1), evaluated from 

 the above equations. 



Strict herbivores 

 Omnivores 



Particle feeders 



Detrital feeders 



Feeders on the 

 detrital milieu 



Strict predators 

 Non-herbivorous 



omnivores 



* for Ki = 0.18, Ks = 0.30, j = 3 



It should be noted that the coefficient N indi- 

 cates only the potential increase of the biomass 

 of each trophic type, as related to productivity 

 input. The potential population (standing 

 crop) depends upon how closely this maximum 

 is approached, and the fecundity, mortality, etc. 

 of the appropriate organisms. 



It should also be noted that the usefulness of 

 the total assumptions of this model can be tested 

 by the determination of R for an appropriate 



trace element, such as Cs, in samples of well 

 defined trophic types. 



LITERATURE CITED 



Young, D. R. 



1970. The distribution of cesium, rubidium, and 

 potassium in the quasi-marine ecosystem of the 

 Salton Sea. Ph.D. Thesis. Scripps Inst, of 

 Oceanogr., Univ. California San Diego, La JoUa. 



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