lower than in the open water (Oradovskiy, 1973), illumination amounts 

 to only a few hundredths of 1% of the illumination on the surface (Bunt, 

 1968). Therefore, only forms adapted to weak light can live in the ice. 

 Actually, the alqae liberated from the ice manifest the maximum photo- 

 synthetic activity at an illumination level of 103 Ix (Bunt, 1968), 1/10 

 that of planktonic representatives of the group (Ryther, 1956). This 

 can be reflected in the productivity of the population. Under natural 

 conditions, the time between divisions in diatoms averages 6 days (Bunt, 

 1968). However, due to the absence of sinking, even with this extremely 

 low development rate, a quite detectable increase in population occurs 

 over the vegetation season. This factor, plus the high content of 

 chlorophyll, resulting from the insufficiency of light, has led several 

 authors to consider the ice flora to be of high significance in the 

 synthesis of organic matter. This is not true. But doubtless, its 

 influence on the pelagic community is quite great. The area of annually 

 thawing ice is some 18 million km^ (49% of the area of the Antarctic zone). 

 As it breaks up, a tremendous quantity of algae enters the water. Many 

 species become true plankters and continue their existence in the water. 

 This intensive "seeding" of the water area as it opens from the ice is 

 of great ecologic significance, facilitating a rapid onset of the bloom. 



Regional differences in the quantity of phytoplankton . Are there 

 differences among regions of the Southern Ocean in terms of abundance of 

 phytoplankton? It is difficult to answer this question, due to the 

 asynchronous appearance of the definite stages of the annual cycle and 

 the briefness of the bloom. A comparison can be made only on the basis 

 of materials collected by the same method, for water areas, the plankton 

 of which is in the identical state of seasonal development, preferably 

 for the period of the maximum or on the basis of multiannual studies. 

 In spite of the limited nature of the available data, some general concepts 

 have been developed with respect to this question. 



The neritic regions, both of the Antarctic and of the Subantarctic 

 zones, are richest. The mean abundance of phytoplankton in the 0-100 m 

 layer during the period of the maximum near South Georgia Island is more 

 than 10 times the mean abundance in the remaining water area south of 

 the Antarctic convergence (Hart, 1942). Since this region was among the 

 first studied, information on it was applied to the entire ocean, and the 

 initial estimates of productivity of the Antarctic were thus far too high. 

 Averaging of a large volume of data on Pacific and Atlantic sectors of the 

 Southern Ocean have shown that, on the whole, the neritic waters are 

 approximately 5 times richer than the oceanic waters (El-Sayed, 1970a). 

 The reason for this is the abundance of trace elements and the intensive 

 consumption of phytoplankton more intensive in comparison to the open 

 ocean. Within the oceanic waters of the Antarctic, there are significant 

 differences between the northern and southern zones. Many observations 

 indicate a significant increase in the maximum in the southern latitudes, 

 particularly in the waters near the ice. It is here that record concen- 

 trations of algae have been observed (Kozlova, 1964; Walsh, 1969; A.I. Ivanov, 

 1959; Hasle, 1969). These differences are apparently based on an increase 

 in the stability of the southern waters, caused by thawing, as well as 

 the "seeding" of the pelagic zone by the flora liberated from the ice 

 (Hart, 1934; Bunt, 1964a). Therefore, the boundary of the rich zone should 



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