16 



G. J. DIVOKY 



Bering Sea 



Little is known about bird distribution in 

 the Bering Sea during ice formation because 

 cruises in rapidly forming ice are potentially 

 hazardous. It is not known if the large num- 

 bers of birds found at the ice edge in March 

 are present in December and January. 



Discussion 



The principal effect of the arctic pack ice is 

 to lower biological productivity and bird den- 

 sities in the areas it covers. Unlike the antarc- 

 tic pack ice, which supports a large biomass of 

 pagophilic species, the number of pagophilic 

 species supported by the arctic pack ice is 

 small. Only the ivory gull, Ross' gull, and 

 black guillemot have specific adaptations to 

 the ice environment. The Ross' gull and guille- 

 mot winter in the pack ice, and the ivory gull 

 is associated with ice throughout the year. 

 The total biomass of these species is low. 

 Other species which are regularly associated 

 with the arctic pack, such as murres and 

 black-legged kittiwakes, are also found in 

 large numbers away from the ice. In addition, 

 these species are usually associated with ice 

 for limited periods during the year murres 

 primarily in winter and spring and kittiwakes 

 primarily in summer. 



The difference in the antarctic and arctic 

 pack ice systems is largely due to the antarc- 

 tic pack ice being surrounded by ocean, where- 

 as the arctic pack ice is, in general, sur- 

 rounded by land. The high productivity asso- 

 ciated with the antarctic pack ice is due pri- 

 marily to the mixing that occurs at the edge 

 of the pack ice. There is little opportunity for 

 mixing to occur next to the arctic pack ice, ex- 

 cept where it is next to large expanses of 

 boreal waters. This occurs in the Bering Sea in 

 winter and spring, in the North Atlantic, and 

 to a minor extent in the Chukchi Sea in sum- 

 mer and fall (Dunbar 1968). The limited geo- 

 graphic range and seasonal nature of high pro- 

 ductivity at the arctic pack ice edge has been 

 a major factor in preventing a well-developed 

 pagophilic avifauna. 



The importance of the in-ice algal bloom and 

 its associated under-ice fauna is not yet clear. 

 It is probably most important in areas such as 

 the Beaufort Sea, where productivity in the 

 water column is low. Although considerable 



numbers of seabirds are regularly found in the 

 summer pack ice feeding on arctic cod and 

 zooplankton associated with the ice, bird den- 

 sities south of the ice are usually greater than 

 those in the ice. The only species that appear 

 to depend on the ice-associated fauna for 

 much of their food are the three pagophilic 

 species mentioned above. 



References 



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 of the nearshore Beaufort Sea, with reference to 

 potential roles of ice biota. Pages 609-632 in J. C. 

 Reed and J. E. Sater, eds. The coast and shelf of 

 the Beaufort Sea. Arctic Institute of North 

 America, Arlington, Virginia. 



Andriashev, A. P. 1968. The problem of the life 

 community associated with the antarctic fast ice. 

 Pages 147-155 in R. I. Currie, ed. Symposium on 

 antarctic oceanography. Scott Polar Research In- 

 stitute, Cambridge. 



Appollonio, S. 1961. The chlorophyll content of arc- 

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Bailey, A. M. 1948. Birds of arctic Alaska. Colo. 

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Barry, T. W. 1968. Observations on natural mor- 

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Bianchi, V. V., and V. N. Karpovitsch. 1969. The in- 

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Bunt, J. S. 1963. Diatoms of antarctic sea ice as 

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 199:1255-1257. 



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Divoky, G. J. 1976. The pelagic feeding habits of 

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Fay, F. H. 1974. The role of ice in the ecology of 

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Fay, F. H., and T. J. Cade. 1959. An ecological 

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Gabrielson, I. N., and F. C. Lincoln. 1959. The birds 

 of Alaska. The Stackpole Company, Harrisburg, 

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