predatory and partially predatory forms-- Metridia Tonga , Calanus g lacialis , 

 C^. h yperboreus , Pareuchaeta spp., large sagittae, mature medusae Aglantha 

 and Cyanea , Ctenophora, Amphipoda--are present in small quantities through- 

 out the year. The growth of biomass in the 0-50 m layer in the high-Arctic 

 zone at first also occurs due to rising of the animals from the depths, 

 then due to their breeding and growth. The number of small predators-- 

 Oithona si mil is and Oncaea boreal is --increases in the summer. The 

 Calanus and G ithona may represent 95-99% of the total number of plankters. 

 The number of Calanus increases beginning in mid-May, decreasing in 

 September, after which the number of small Copepoda increases. The popu- 

 lation peak of the relatively larger meduses and ctenophores occurs in 

 April-May, of the smaller forms--in July-August, synchronously with the 

 Appendicularia. The fraction of predators in high-Arctic waters is high: 

 The number of mature large predators is only one or two orders of magni- 

 tude less than the number of Calanuses . The total biomass, from 20 mg/m^ 

 in late March, increases to 250 in the second half of April -May and 400 in 

 August, dropping to 200 in late September and then rapidly decreasing to 

 the winter values (data for the northern area of the greenland Sea). The 

 winter stock inhabits the lower layer, dropping to depths of over 1000 m. 

 The various species descend at different times. The Metridia , Microcalanus , 

 Pareuchaeta , and Spiratella breed in the winter. In zones with intensive 

 horizontal movement of masses of water (e.g., Scoresby Sound), the 

 indigenous plankton reaches only 13% of its summer population maximum 

 (Digby, 1953). In the epicontinental seas and on the shelf, the vernal 

 maximum consists more than 70-80% of indigenous populations. 



2.4. Perennial Changes in the Biomass of Zooplankton of the 

 Arctic Pelagic Zone ~~~ 



The productivity of the Arctic community is a resultant quantity from 

 a complex net of biotic relationships, functioning against the background 

 of cyclic changes in abiotic factors. Both the deep-sea and the shelf 

 and neritic water areas represent quasi-stable fields of production with 

 definite gradients in space and time, preserved from year to year and 

 generally independent in the temperature aspect. Thus, in the Norwegian 

 Sea in 1959-1963, the mean annual values of biomass and production 

 of zooplankton for the sea as a whole differed from year to year by a 

 factor of not over 2 (Timokhina, 1968, 1972). In the Barents Sea in 

 1934-1939, the mean annual indicators were approximately the same 

 (Yashnov, 1940). The production is invariably highest in the Arctic and 

 shore waters (averaging 55 t/km^) and lowest in the warm Atlantic waters 

 (averaging 9 t/km^). The maxima of production and biomass of the dominant 

 species occur in various water masses, or diverged vertically or horizontally 

 through a single mass of water (Zelickman, Kamshilov, 1960; Zelickman, 

 Golovkin, 1972; Timokhina, 1968). 



An analysis of a representative series of 22 years of almost monthly 

 plankton samples collected by a Longhurst-Hardy automatic plankton 

 sampler at a depth of 10 m in the north Atlantic showed no clear connection 

 between climatic changes and seasonal fluctuations in the abundance of 

 zooplankton. It showed only that various species or groups of species have 



61 



