5.4.1 Complex Ecological Evaluation of 



Planktonic Communities of the Pelagic 

 Zone 



ALLA V. TSYBAN, ANDREY S. KULIKOV, MIKHAEL N. KORSAK, VASSILIY M. KUDRYATSEV, and 



VLADIMIR M. VENTSEL 



Institute of Global Climate and Ecology. State Committee for Hydrotneteorology and Academy of Sciences, Moscow, USSR 



Introduction 



Population-biocenotic effects of anthropogenic impacts 

 of the marine environment, the detection of which is necessary 

 to characterize the ecosystem stability level, are reflected in the 

 structural and functional characteristics of its communities. 

 However, natural communities also can cause the reconstruction 

 of the processes of the functioning and structure of the ecosystem 

 biotic component. At the current level of knowledge in this 

 field, it is difficult to distinguish between the results of 

 anthropogenic impact and natural variability. It is only possible 

 to solve this problem in the course of long-term observations on 

 the basis of data on the background levels of the structural and 

 functional characteristics (Izrael & Tsyban, 1989). 



Structural characteristics include evaluation of the species 

 composition, numbers, and biomass of different systematic 

 dimensional and trophic groups, as well as spatial and temporal 

 variability of these parameters. Functional characteristics 

 include the energy flux through communities, which are formed 

 at the expense of productive and destructive processes, as well 

 as trophic relations between the components of communities. 



A great body of data characterizing the structure and 

 functional processes of the basic elements of plankton 

 communities was determined on comprehensive ecological 

 expeditions in the Bering Sea ( Izrael & Tsyban, 1990) organized 

 by the Natural Environment and Climate Monitoring Laboratory 

 in June 1981 and jointly with American specialists in 1984. 

 These data have formed the basis for estimation of the integral 

 characteristics of the status of the plankton communities 

 inhabiting the epipelagic in the Bering Sea, carried out on the 

 basis of the analysis of trophic relations between their elements. 

 Calculations of the parameters of the production-destruction 

 processes of zooplankton present an important stage in this 

 work. 



Materials and Methods 



Our work is based on the data obtained during the 

 comprehensive ecological investigations carried out during the 

 expedition in the Bering Sea on board the RA^ Akademik 

 Shirshov in June 1 98 1 and RA' Akademik Korolev in July 1 984 

 on the South, East, and West Polygons (Fig. I ). During the 

 investigations, the basic structural characteristics of the plankton 

 inhabiting the surface 100-m layer (numbers and biomass of 



bacterioplankton; species composition, number, and biomass 

 of phyto-, microzoo-, and mesozooplankton) and functional 

 ones (primary and bacterial production) were detennined. 

 Results of the analysis of the data characterizing the status of 

 individual dimensional-trophic groups of the Bering Sea 

 plankton community and the description of the methods used 

 in investigations have been published in the monographs 

 (Izrael & Tsyban, 1987) and some papers (Moisyev, 1987). 



The ration and production of the heterotrophic link of 

 plankton communities was calculated in accordance with a 

 scheme developed in the plankton laboratory of the 

 P. P. Shirshov Oceanology Institute of the USSR Academy of 

 Sciences ( Vinogradov (feShushkina, 1987). The authors believe 

 this to be the only acceptable method for determining the 

 production values of heterotrophic elements of multispecies 

 plankton communities in the ocean pelagic region, consisting 

 of populations with an extended period of reproduction and 

 functioning in conditions of limited food resources. 



The preparations of data for the calculations consisted, 

 first, in separating out the elements of the communities with 

 allowance for taxonomic, dimensional, and trophic 

 particularities of the biota. Analysis of the trophic composition 

 of zooplankton and communities, as a whole, was carried out 

 using the literature data describing food interrelations in the 

 epipelagic zones of subarctic and highly productive regions of 

 the World Ocean (Petipa, 1981; Cooney & Coyle, 1982; 

 Vinogradov & Shushkina, 1987). The results of the analysis 

 made it possible to isolate nine basic elements in the Bering Sea 

 plankton (Table 1 ) and evaluate the relations between them 

 from the degree of the use of different kinds of food by various 

 consumers (Table 2). The scheme of trophic relations includes, 

 apart from the elements, dead organic matter (d+y ) that resulted 

 from the vital activity of hydrobionts and could be consumed 

 by them again. The feeding selectivity coefficient J assumed 

 the values 1.0, 0.5, 0.2. and 0, which corresponded to the 

 following gradations: "consume fully," "consume partially," 

 "consume little," and "do not consume at all" (Vinogradov & 

 Shushkina, 1987). In the case when all organisms making up 

 the consumer element ( i ) are able to consume all the organisms 

 making up the prey element (j). the coefficient was given the 

 maximum value of 1 .0. The ability of one consumer to use a 

 variety of the objects making up the prey elements for food, J 

 was given the value 0.5 or 0.2. If there is no trophic relationship 

 between the elements, J = 0. 



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