where P^- is production of different elements of the community from 

 phytoplankton (p) to carnivores (s), D^ - nonassimilated food; C^- - 

 value of food consumption; U"-'- - food assimilability . 



Both equations (3.2 and 3.3) are practically the same. 



It is possible to calculate the part of community production that 

 may be utilized by higher trophic levels not accounted for in the 

 calculations (carnivorous fishes, squids), or by any other form of 

 exploitation (Shushkina, 1966; Klekowski, 1970). 



It is real community production (P^,): 



P2 =.l Pi -.LCi (3.4) 



i=a i=f 



where P^ is production of different elements of community from 

 protozoans (a) to predatory animals (s) and C^- is value of food 

 consumption of the elements from herbivorous animals to predators. 



The rate of production of a planktonic community can be calculated 

 using equation (3.4) if the community includes only a small number of 

 species, interrelated primarily by the trophic chain. Communities of 

 this sort are relatively frequently seen in fresh and marine bodies of 

 water in the temperate and high latitudes. However, in this case as 

 well, the calculation of the production of zooplankton is rather 

 difficult, since it requires us to consider the influence of such 

 environmental factors as temperature, concentration of food for each 

 element of the community, etc., on all of the parameters included in 

 equation (3.4). Calculations of production for an entire tropic pelagic 

 community, consisting of hundreds of species, interconnected in a 

 trophic chain, are practically impossible without the use of 

 mathematical modelling and computers. 



The method of mathematical modelling in combination with 

 radiocarbon and physiologic methods, can be used to estimate the rate of 

 production of individual specific populations (Shushkina et al . , 1974), 

 the trophic levels of zooplankton and the planktonic community as a 

 whole (Shushkina, Kislyakov, 1975). Such a combination of different 

 methods was, for example, used to estimate the productivity of pelagic 

 communities of the Sea of Japan (52nd cruise of the VITYAZ) and the 

 equatorial zone of the Pacific Ocean (17th cruise of the AKADEMIK 

 KURCHATOV). The essence of the approach is that at the level of maximum 

 concentration of plankton, large (140 i) water bottles of organic glass 

 collect samples of water, including a known quantity of phytoplankton, 

 preliminarily labeled with radiocarbon to a constant level. After 10 or 

 12 hours exposure of the water bottle at the same depth during the dark 

 hours of the day, the concentration N, dimensions i, weight W and 

 radioactivity G of organisms of the phytoplankton, bacteria, protozoa 

 and individual systematic or trophic groups of zooplankton (fine filter 

 feeders, small herbivores, cyclopoids, predaceous calanoids, etc.) are 

 determined. A plan is then constructed of the basic trophic connections 



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