LANGE and HURLEY: UNSTRUCTURED FOOD WEBS 



Similarly, for detrital feeders 



and for predators 



ApU^ = 



All of Isaacs' other equations for trophic level 

 potential biomasses or fluxes can be obtained in a 

 similar manner. 



Equations for the potential biomass of trophic 

 levels can also be calculated for the generalized 

 model. This is done in a manner similar to that 

 described in the previous section. 



Strict herbivores (feeding on source): 



Mm =M^k,. 



Omnivores (feeding on source, living and re- 

 trievable dead): 



M = M I -^l(^8-l) + ^2^7 



'\ik,-l){k,-l)-k,k, 



= k^MQ + k^ M\ + k^M'l. 



Particle feeders (feeding on source and re- 

 trievable dead): 



M^=Mo 



k,{k,-\){k^-l) + k^k,{\-k,) 

 {k,-l){k,-l)-k,k, 



= kiMQ + kr; M'l . 

 Detrital feeders (feeding on retrievable dead): 



M, = M. 



-k^k-jk^ + k^krj + k^k^krj 

 ~lk,-l){k,~l)-k,k, 



= k^ M'[. 



Full predators (feeding on living): 



Mp = M, 



-k^k^ {k^-\) + k^ k2krj 



« > (Z:4-l)(^8-l)-^5^7 

 = k,M', 



Nonherbivorous omnivores (feeding on living 

 and retrievable dead): 



M = M /~"'4"'i"'8 + k^k^ + k2k'j + k-^k^k^j 



{k,-l){k,-l)-k,k, 



= k^M'f + kjM';. 



ACKNOWLEDGMENTS 



This work w^as partially supported by Public 

 Health Service Grant NS-09342. We would like to 

 thank the following people for reading the 

 manuscript and making valuable comments: J. D. 

 Isaacs, G. Wick, J. Enright, P. Hartline, and M. 

 Mullin. Thanks are also due E. Venrick who 

 brought the problem to our attention and the other 

 students in NS 242 who patiently allowed us to 

 work out the model as a classroom example. 



LITERATURE CITED 



Isaacs, J. D. 



1972. Unstructured marine food webs and "pollutant 

 analogues." Fish. Bull., U.S. 70:1053-1059. 



1973. Potential trophic biomasses and trace-substance con- 

 centrations in unstructured marine food webs. Mar. Biol. 

 (Berl.) 22:97-104. 



Young, D. R. 



1970. The distribution of cesium, rubidium, and potassium 

 in the quasi-marine ecosystem of the Salton Sea. Ph.D. 

 Thesis, Univ. California, San Diego, 234 p. 



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