do not form such abundant concentrations as the phytoplankton , cannot, 

 under the sharply variable environmental conditions, be very productive. 

 The absence of the strong pressure of predators, in turn, may help to 

 maintain the low level of specific variety (Paine, 1966). 



All of this shows the great length of the chain of results which 

 follows from the basic peculiarity of the biotopes of the temperate 

 and polar latitudes--the seasonal change in solar radiation. First of 

 all, it assures that the production process is discontinuous, which in 

 turn defines the basic features of the zoocenes: the character of their 

 annual cycles, the level of specific variety, their trophic structure. 

 Therefore, the seasonal changes in solar radiation can be considered 

 the most important factor determining the peculiarities of cold-water 

 ecosystems . 



The trophic web . The structure of the trophic web of the Southern 

 Ocean is relatively simple. The phytoplankton is consumed by copepods, 

 euphausiids and tunicata. All of these are nonselective filter feeders. 

 The copepods and euphausiids are consumed by the hyperiids, chaetognaths , 

 predaceous copepods, squids, fishes and baleen whales. The fishes and 

 whales also consume amphipods. The fishes and squids are consumed by the 

 sperm whales and small toothed whales. A definite role in the consumption 

 of the pelagic fauna is also played by the pinnipedes: the crab-eating 

 seal feeds almost exclusively on krill, the other seals--on cephalopods 

 and fishes. Only the Baqridae and sea leopard attack homoiotherms in 

 the Antarctic. 



All of these food chains are of the grazing type. The significance of 

 detrital chains, which begin with the utilization of dead organic 

 matter, as well as heterotrophic bacteria in the Antarctic and Subantarctic, 

 is very low. 



This trophic web consists of four main levels: producers, phyto- 

 phages, and first and second order predators. The baleen whales, fishes 

 and marine birds, which consume the phytophages and small predators, 

 occupy an intermediate position between the last two levels. Unfortunately, 

 this system has no quantitative characteristics, since the production, 

 and even the biomass, of many groups of organisms, are as yet unknown. 

 Only approximate data can be presented. The most realistic figures 

 seem to be as follows. The mean annual biomass of net plankton 

 (mesoplankton) in the Antarctic in the 0-1000 m layer is 26 mg/m^ (Foxton, 

 1956), while in the period of the summer maximum, in the upper 100 meter 

 layer, in the Indian and Pacific Ocean sectors it reaches 10-20 g/m^ 

 (Voronina, 1966b). The greatest mass is that of the copepods (73%), followed 

 by the chaetognaths (10%) and euphausiids (8%) (Voronina, 1966c). The 

 biomass of euphausiids, according to trawl data, is about 0.7 g/m^ 

 (Dolzhenkov, 1975), and in regions of their greatest abundance--up to 

 30 g/m2 (Marr, 1962). The biomass of whales during the period of their 

 abundance was 0.56 g/m^, their consumption of plankton over the summer 

 season about 10 g/m2 (Nemoto, 1968; Mackintosh, 1973). 



At the present time, a radical restructuring of the quantitative 

 relationships between individual elements in this web is occurring. 



101 



