varying tendencies of changes in their number within and between years 

 (Colebrook, 1972a, b). The greatest limits of variability in numbers are 

 seen as we compare different species; the differences are significantly 

 less when we compare plankton as a whole for different months, least of 

 all when we compare different years (Colebrook, 1972a, b). The number of 

 Copepoda before the beginning of the spring development differed in 

 different years by a factor of less than 2, regardless of the preceding 

 and subsequent peaks. The times of appearance of the maxima in the numbers 

 of Copepoda, the duration of the peaks and the scale of the second, 

 usually smaller, maximum were more variable. 



Of particular interest for a general description of the ecosystem 

 is the slight variability of annual production indicators (Table 2). 



This variability from year to year is somewhat greater in the shallow 

 southeastern area of the Barents Sea (Table 3), where the significance of 

 invertebrate predators is somewhat greater, decreasing the summer-autumn 

 biomass to 1/4-1/5 of the previous level (Nesmelova, 1968; Zelickman, 

 1961c). 



The relative constancy in the values of production is maintained by 

 various mechanisms which standardize the population, acting primarily on 

 the early stages of ontogenesis. For example, the relative constancy of 

 the number of Calanus nauplii indicates constancy of the number of breeding 

 females, capable of maintaining the initial numerical level of nauplii. 

 The number of Calanus nauplii in a cross section through the Kola meridian 

 in May (Degtyareva, 1972) is given below: 



In 40 years of studies of plankton of the Barents Sea, samples were 

 taken during periods of cooling and warming of the Arctic, covering various 

 stages of activity of the fishing industry, changing the plankton consumers. 

 Therefore, it is useful to look at a few more figures. In the southwestern 

 Barents Sea during the warming trend (1929-1937), the biomass of zooplankton 

 in the 0-50 m layer averaged 5-15 mg/m3 in December-March, 100-200 mg/m3 in 

 April, 500-900 mg/m^ in June, with the individual maximums rising to 5000 mg/m^ 

 (Manteyfer , 1939, 1941; Yashnov, 1939, 1940). It remained approximately 

 the same in 1954-1969, which saw both very warm and \jery cold years. In 

 the southeastern portion of the Norwegian Sea, the biomass was the same 

 during warm (1927-1939) and cold (1949-1951) years (Wiborg, 1954). Along 

 the shores of Spitsbergen in 1959-1966, the seasonal and annual total 

 volume of plankton in the 0-25 m layer varied by approximately an order of 



62 



