Fig. 13. Seasonal changes in the 

 stability of the 0-100 meter layer 

 in the northern region of the 

 Antarctic (Currie, 1964). 



M It XT ! 



IV IS 

 M 7 



the configuration of the coastline modifies the drift of the ice, causing 

 its accumulation on the eastern sides of projecting parts of the coast, and 

 milder conditions on their western sides (Yeskin, 1969); the specifics of 

 the edge of the shelf and of the deep water circulation lead to the fact 

 that in some places the southern waters become free of ice earlier than 

 the more northern. All these peculiarities disrupt the latitudinal 

 sequence of the hydrologic and biologic seasons. Along with the main 

 seasonal maxima of phytoplankton, other maxima may exist, e.g., at the 

 edge of the ice or near icebergs (Kozlova, 1964; Steyaert, 1973; Voronina, 

 Zadorina, 1974). The time of the bloom may change from year to year in 

 the same place. For example, at 20°E in January of 1967, the maximum 

 population of diatoms was located some 6° further north than in January 

 of 1965. Such deviations make the average picture of seasonal changes in 

 the quantity of phytoplankton smoother; therefore, in order to judge the 

 true amplitude, measurements must be made during the extreme periods. 

 There are little data suitable for comparison, due to the great variety 

 of methods which have been used for collection and processing of phytoplank- 

 ton and for the presentation of results. Therefore, here and below, in 

 order to describe the quantity of phytoplankton, in addition to the 

 number of cells, we will also use information on plant pigments, and-- 

 at times--on primary production. 



In the winter, beneath the ice, there ixv& practically no algae. In 

 the open water in the Antarctic, the concentration of plant pigments is 

 about 50 Harvey units per cubic meter, the mean monthly quantity of 

 chlorophyll "a" at the surface is not over 0.1 mg/m^, decreasing in places 

 to 0.01 mg/m^ (El-Sayed, 1970a). During the period of the phytoplankton 

 bloom in the Antarctic waters, the number of diatoms at the surface reaches 

 1-4-105, and even 10^ indiv. /liter (Fukase, 1962; Zernova, 1970; Steyaert, 

 1973: Marumo, 1957; Kozlova, 1964). The mean number of algae in the upper 

 100 meter layer is on the order of 10*^-105 indiv. /I iter (Sanina, 1963; 

 Steyaert, 1973). The concentration of plant pigments during this time may 

 exceed 5-10'^ Harvey units per cubic meter (Hart, 1942); the concentration of 

 chlorophyll "a" exceeds 15, reaching 123 mq/m^ (El-Sayed, 1968a, 1970a, b); 

 the biomass of wet seston, strongly dominated by phytoplankton, may reach 

 27 g/m3 (A. I. Ivanov, 1959) and 56.5 cm^/m^ (Marumo, 1953). Even beneath 

 non-thawing ice, at the time of breakup of its lower surface, the popula- 

 tion of the P haeocystis reaches 1 million cells/liter (Bunt, 1964b). In the 

 Subantarctic at 20 E, during the bloom, the population of diatoms in the 

 upper 100 meter layer has been observed as high as 3.4-105 cells/liter 

 (Steyaert, 1973), to the southeast of the Falkland Islands--! .5-lo7 cells/ 

 1 iter. 



84 



