2.5 Changes 1n Functional Characteristics 



The succession changes in biomass and trophic structure of communities 

 are closely related to changes in their functional characteristics. The 

 difficulties of quantitative evaluation of most of these usually force us 

 to give only a qualitative estimate of many functional characteristics. 

 However, the efforts expended in recent years in the study of pelagic eco- 

 systems have in many cases allowed quantitative characterization of the 

 succession changes in production not only for the lower trophic and ecologic 

 groups (phytoplankton, bacteria), but also for higher levels and for the 

 entire community as a whole, as well as estimation of the changes which 

 occur in the course of succession in a number of other functional parameters; 

 the degree of satisfaction of the demand for food (6), the stress on trophic 

 connections [e, or k), the degree of balance of production and consumption 

 of various trophic levels (e) and their ecologic effectiveness (w).* 



*According to Slobdkin (1961), Menshutkin (1971), Vinogradov et al . 

 (1976), 6 = Ri/R*^^^, where R^ is the actual ration, i.e., the food which an 

 animal can consume given the available prey, R^^^ is the maximum ration, 

 i.e., the quantity of food which the animal could consume to support its 

 maximum growth rate. 



" max 



r' III 

 I'^i 



1 



J -Pj 



" max 



where ^^r^^ is the sum of the particular maximum rations of consumers, 



i 

 Pj is the production and Bj is the biomass of prey; 



n 



max 



v.. = is the index defining the pressure of 



predators on the biomass of a given prey species. These last two parameters 

 show the extent to which, under the conditions present, organisms of the j^^ 

 group can be consumed and the extent to which the food requirements of 

 consumers can be satisfied by the production of the prey; 



^j 



Pj 

 -^ — is the ratio of prey production to the sum total 



i^u 



of the particular rations of predators, and shows the extent to which the 

 production of a lower trophic level is utilized by organisms of the sub- 

 sequent trophic levels; 



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