measured. The mean daily P/B coefficients for most mesoplanktonic 

 animals have been found to be 5-15%, corresponding to the data of other 

 authors (Greze, 1971, 1973a, b; Malovitskaya, 1971, 1973). It should be 

 emphasized that the physiologic method using values of Ko constant for 

 the entire population and ignoring the specifics of the food, the 

 pressure of predators and other factors which influence the values of 

 production, can produce only approximate values of production and P/B 

 coefficients. A more precise estimate of the level of production can be 

 obtained by combining the physiologic and radiocarbon methods with 

 mathematical modelling in experiments in situ. This type of estimate 

 has been made for the planktonic animals of the Sea of Japan (Shushkina 

 et al., 1974) and the equatorial region of the eastern Pacific 

 (Shushkina, Kislyakov, 1975). The results of the determinations (Table 

 15) in some cases were close to the values determined by other methods, 

 for example for the copepodites of Calanus plumchrus (Parsons et al . , 

 1969) and the chaetognaths (G. N. Mironov, 1970, 1973; Zaika, 1969). 

 However, most of the determinations differed significantly from the 

 values produced earlier for closely related animals (Greze et al., 1968; 

 Malovitskaya, 1971, 1973). Since the P/B coefficients which were 

 compared were produced by different methods for different species of 

 animals differing in their size and conditions of life, close similarity 

 of the P/B coefficients should not be expected. 



It is thought that the intensity of production depends on 

 temperature conditions, since they determine the growth rate and 

 breeding rate of animals (Mednikov, 1965; Zaika, Malovitskaya, 1967; 

 Reeve, 1970; and others), the availability of food (Winberg et al . , 

 1965; Shushkina, 1966; Menshutkin, 1971) and the dimensions of the 

 animals (Zaika, 1972). This last variation--the increase in rate of 

 production with decreasing size of the animals--is, apparently, general 

 in nature. 



The results of estimation of the intensity of production of 

 populations and individual systematic groups of planktonic animals do 

 not allow us to make a judgement concerning the rate and intensity of 

 production of entire trophic levels, of zooplankton and of the plankton 

 as a whole, which is most important in the study of the production 

 characteristics of aquatic communities. Very few estimates of this type 

 have been made for marine plankton (Mednikov, 1960; Petipa et al . , 1970; 

 Greze, 1970, 1971, 1973a; Vinogradova, Gruzov, 1972; Shushkina, 

 Kislyakov, 1975; Vinogradov et al . , 1976; V. D. Fedorov, 1970). 



As an example, let us present the results of estimation of the 

 productivity of various levels of the planktonic community in the upper 

 (0-150 m) layer of water in the equatorial region of the eastern 

 Pacific, obtained by combining the physiologic method with mathematical 

 modelling [equations (3.1-3.5)]. The material was collected during the 

 17th cruise of the AKADEMIK KURCHATOV in 4 measurement areas with 

 trophicity decreasing from east to west. The planktonic community was 

 subdivided into: phytoplankton, bacteria, protozoa and mesoplankton. 

 The phytoplankton was subdivided into small (cell diameter < to 15 urn, 

 volume < 1,000 \sn^) and large (diameter > 15 m, volume > 1,000 pm^) . 

 The bacteria, which represented a single trophic level in our example, 



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