etai, 1984; Vinogradov &Shushkina, 1987) — that is, bacteria 

 consume, besides autochthonous organic matter, as much 

 allochthonous organic matter as they need to meet their 

 requirements for food in conditions of production of this 

 element, determined experimentally, and in order that the 

 production calculated on the above scheme corresponded to 

 that determined experimentally (Shushkina era/., 1984b). Itis 

 assumed that allochthonous organic matter consumed by other 

 elements of the community is far less than that consumed by 

 bacterioplankton, and it is not taken into account in the 

 calculation scheme. 



The method makes it possible not only to estimate the net 

 production of the community [P(0)] equal to the difference 

 between the primary production formed at the entrance into the 

 system [P(p)] and the heterotrophic destruction of the 

 community D^, = Z R,, but also to estimate the actual 

 production of the conmiunity, P^,,, which takes into account at 

 the beginning the primary production and allochthonous organic 

 matter arriving to the trophic chain the bacterial link: 



P„ , = P„+rbx-D,. 



(10) 



where r(bx) is the ration of allochthonous organic matter. 



There following tropho-ecological characteristics of the 

 elements and community as a whole (Vinogradov & Shushkina, 

 1987) are used in the work: 



— the degree of the satisfaction of requirements in food of the 

 consumer element (i): 



S, = c/c,"'''' (ID 



— real specific production of the prey element (j): 



^' B, (12) 



where 2x0 = 1 day: and the ratio of the energy assimilated by 

 bacterioplankton and other detritophages to the total energy of 

 detritus energy and phytoplankton assimilated by all the 

 heterotrophic parts of the community: 



i A,(d+y) 



P =1 — '^ s (13) 



• §,A,(d+y)4.Z A, 



As a criterion for determining the trophic character of 

 waters, use was made of the ratio of the primary production 

 level to the overall heterotrophic destruction level 

 [Kjp = Pp / D„] according to the following ranges of the 

 coefficient values: K(3p) > 2, hypertrophic; 2 > K(3p) > 0.7 

 eutrophic; and 0.7 > K(3p). oligotrophic water (Lebedeva, 

 etal., 1982; Vinogradov & Shushkina, 1983). 



Results 



The values of the structural and functional characteristics 

 of the plankton community found m the epipeiagic region of 

 the southwestern Bering Sea at South and East Polygons 

 consisted of 719^ mesozooplankton hydrobionts; the portions 

 of other dimensional and functional groups accounted for 10% 

 each. 



The results obtained have indicated that the community 

 under consideration was at the destructive stage of the seasonal 

 development and experienced a deficiency of newly formed 

 organic matter. The amount of energy necessary to maintain 

 the vital activity of heterotrophic elements lD(o)] was nearly 



four times more than the energy arriving to the community as 

 a result of photosynthesis of phytoplankton [P(p)], which 

 determined respectively the negative values of the net production 

 of the community [P(o)]. Its average level was 

 -1 1.8 kcal/m- day. The average values of the coefficient of the 

 primary production of the community [K(3p)] made it possible 

 to place the waters of the study areas into the category of 

 mesotrophic waters. It should be noted that 74% of the values 

 of the overall heterotrophic destruction consisted of the 

 respiration expenditure by bacterioplankton. 



Energy of allochthonous organic matter arriving to the 

 community though the bacterial link fully covered a shortage 

 of the production of autotrophs. As a result, the actual production 

 levels of the community [P(act)] had positive values and 

 amounted to an average of 4.9 kcal/m- day. 



Functioning of the zooplankton elements of the community, 

 in such a situation, was based to a great extent on the detrital 

 food chain. The amount of the energy of dead organic matter 

 assimilated by heterotrophic accounted, on average, for 

 53% of the total volume of the energy (p) assimilated by 

 heterotrophs. 



Only 29% of the total ration of zooplankton consisted of 

 phytoplankton. The basis objects of its food were the following 

 heterotrophic elements: bacterioplankton (24%) and small 

 zooplankton (37% ). The existence of the communities under 

 conditions of a deficiency of newly formed organic matter 

 caused a certain tension in the trophic relations, which was 

 reflected in a comparatively low degree of satisfaction of the 

 food requirements of zooplankton (5): 73%, on average, for 

 infusorians and 81% for mesozooplankton, as well as in the 

 negative values of the rates of real production (t, ) of micro- and 

 mesozooplankton. This indicates a tendency for an increase in 

 biomass of these elements. 



Unlike the polygons located in the southwestern deep- 

 water region of the Bering Sea, the North Polygon was 

 characterized by the status of the plankton communities in two 

 kinds of water masses of different origin and having different 

 hydrological indices, namely, the waters of the central shelf 

 (the central and south areas of the polygon) and the waters of 

 the Anadyr Current (the north area of the polygon) (Izrael & 

 Tsyban, 1990). In this connection, the structural and functional 

 characteristics of the plankton communities discovered in the 

 region of the North Polygon differ greatly from those calculated 

 for the community of the epipeiagic regions of deep-water 

 areas of the Bering Sea and were different inside the polygon; 

 the characteristics of its north region differed appreciably from 

 those in its southern part (Table 3). 



In the waters of the Anadyr Current (the northern part of 

 the North Polygon ), the community was at the clearly expressed 

 production stage of succession. Its total biomass [B(o)] was 

 maximum over the whole w ater area of the sea and amounted 

 to an average of 61.3 kcal/m-. The biomass of phytoplankton 

 makes up more than two-thirds of this volume; the remaining 

 part consisting of mesozooplankton content of the pelagic 

 region was not significant. 



The production of phytoplankton was almost four times 

 more than the overall magnitude of destruction of organic 

 matter. The magnitude of production of the community [P(o)J 



204 



