succession leads to restoration of the number and role of the 

 dominant species. This type of change is characteristic of 

 Riiditapes philippiuanon biocenosis in the Gulf of Possiet that 

 is periodically subjected to an invasion of enormous numbers 

 of the sea star Asterias amureiisis that devour practically all 

 adult individuals of those mollusks in the biocenosis. 



Finally, the reversible type of replacement of dominant 

 species with a long life cycle may occur due to shortage or a 

 complete lack of a usual replenishment with young individuals 

 of the population. In this case, non-occurrence of generations 

 for several years may lead (at a natural limitation of older 

 individuals) to a drastic decrease of biomass of the dominant 

 species — in this case, former subdominant species with long 

 life cycles become dominant. In addition, several species with 

 short life cycles that manage to achieve a rapid and sufficient 

 increase of their biomass due to absence of competition may 

 also become dominant and increase their role in the biocenosis. 



Later on, with aging of young individuals of the former 

 dominant species of the biocenosis, it can regain its domination. 

 In this case, its domination goes on until the new unfavorable 

 period begins. This situation may be jeopardized if there is 

 more than one dominant species. 



Which of the various mentioned types of change in 

 dominant species is characteristic of the Gulf of Anadyr is 

 unknown. Only with continued studies of this biocenosis, on 

 annual and interannual time scales, will we be able to determine 

 the causes for the changes in benthic composition in this arctic 

 system. 



The authors would like to thank J. Grebmeier and D. Adkison for 

 their kind and interested assistance in collecting benthic samples in the 

 wilderness of the Arctic. We would also like to thank G. N. 

 Bouzhinskaya, S. D. Crebelny. A. G. Bazhin. and V. V. Tomanov for 

 a prompt analysis of material. 



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