Buktevich shows in the bacteriological research in the Greenland, Barents and Kara Seas that 

 the greatest quantity of bacteria was found first in the regions of the contact of water masses of 

 different physico-chemical character, and secondly, in regions of melting ice. The first is ex- 

 plained by the fact that the mixing of different waters creates unfavorable conditions for the plankton 

 organisms which are typical of each separate water mass. The plankton thus partially die off and 

 are thereby transformed from consumers of bacteria into material for feeding the bacteria. The 

 second is explained by the accumulation of bacteria in the ice, as described above. This is best 

 demonstrated by the following figures: 



According to Buktevich, during the expedition of the Sadko in 1935, in one of the summer 

 water puddles on the ice there were found 60, 000 bacteria in 1 cc of water, while the maximum 

 quantity of bacteria found in the waters of the Greenland, Barents and Kara Seas did not exceed 

 27, 000 in 1 cc. 



As has already been noted, a part of the dissolved nutritive material and organic matter is 

 exuded back into the water together with the brine, but the larger inclusions remain in the ice and 

 finally appear on its surface. Actually, as we have seen, the ice is formed from beneath, melts and 

 is destroyed from the sides and top. It is estimated that in the Arctic Basin approximately the same 

 quantity of ice accumulates by freezing from beneath. Thus, every particle frozen into the ice from 

 below will appear on the surface in two to three years. 



In the spring when the small puddles of thaw water are formed on the ice fields, the micro- 

 organisms and in particular the plant life which have retained their vitality during their stay in the 

 ice find unusually favorable conditions for their development in these small lakes — an abundance of 

 light and an abundance of nutritive matter. 



According to Palibin, little is yet known concerning the biology of this group of organisms. 

 They are usually differentiated by the color which they impart to the snow or ice. The usual color 

 of fresh-water or sea-ice organisms is yellow or dark yellow. This is explained by the large 

 quantity of fat in the cellular content, facilitating the absorption of solar energy in the summer and 

 somewhat protecting the organism from cold in the winter. In addition to yellow, there are also 

 found green, red, and even black colors, due to the presence of various pigments in the cellular 

 content of the organisms' protoplasm. 



Thus, for example, the alga Spherel ia nivalis causes a reddish tint in the snow in the 

 second half of the summer, while the alga Rasphidonoma navale causes a greenish tint. 



Besides the forms which exist in the ice, certain micro-organisms which are peculiar to sea 

 ice develop during the summer in the ice itself and around it, and form communities. These are 

 called "ice plankton" or "cryoplankton". Most important of the growing and living organisms is the 

 group of ice diatoms of rounded or rhomboidal shape, very distinct from the usual forms of the 

 open sea. 



Diatoms as a rule are not found in a living condition on the ice surface, and the reddish -brown 

 ice conditioned by the diatom colonies may be seen only at a certain depth (about a meter) on the 

 bottoms of puddles which have formed on large floes, in cracks of the ice, and on the underwater 

 projections of occasional floes. 



Nansen notes that in the Arctic Ocean, when puddles of thaw water are formed on the ice sur- 

 face under the influence of the sun's rays, dark patches appear on their bottoms. These patches 

 consist of algae, mainly diatoms. 



306 



