Before turning to an analysis of the biocenoses of the eutrophic 

 North Pacific, let us briefly discuss the peculiarities which 

 distinguish the deep-water (abyssal) biocenoses of the ocean floor from 

 biocenoses of the shelf zone, and analyze the basic aspects of abyssal 

 biocenoses of the eutrophic zone of the ocean. 



The tremendous size of the abyssal zone biocenoses is one of their 

 most important specific features. Such factors as depth, bottom relief 

 and composition of bottom sediment change smoothly in the abyssal zone, 

 seasonal and diurnal fluctuations in temperature and salinity are 

 absent, as are tidal movements of the water. Soft sediments 

 predominate, constant currents are slow. In accordance with this, the 

 boundaries of the biocenoses are not sharp, and each biocenosis is 

 large. 



A second peculiarity of abyssal biocenoses is the sparsity of 

 macrofauna and megafauna, in spite of the almost continuous distribution 

 of the infaunal meiobenthos in the surface layer of the bottom 

 deposits. This means that the relative quantitative impoverishment of 

 the bottom fauna is great, since the biomass of the meiofauna does not 

 compensate for the low biomass of larger animals. The specific variety 

 of the benthos in the eutrophic zone, however, is rather great. 



One peculiarity of the systematic composition of benthic fauna! 

 biocenoses of the sea floor might be considered a third peculiarity of 

 abyssal communities. Particularly characteristic are those morphologic 

 features of organisms which are related to the shortage of calcium at 

 great depth, the limited food supply, life in total darkness with very 

 slow movement of the water, in an environment with predominantly soft 

 sediment and high hydrostatic pressure, influencing the rates of growth 

 and metabolism, etc. All of this influences the general appearance of 

 deep water inhabitants; therefore, the abyssal biocenoses differ from 

 shallow-water biocenoses not only in terms of specific composition, but 

 also in terms of the general appearance of the component species. 



There are a number of species and genera, less frequently families, 

 which are found only in the abyssal areas, making up the ancient core of 

 the oceanic complex of benthic fauna. These include the glass sponges 

 (Triaxonida) , polychaeta from the genera Macellicephala, 

 Macellicephaloides , Kesun , Jasmineira , Maldanella ; bivalve mollusks from 

 the genera MalletTa , SpirTula , Parayoldiella , Ledella , Vesicomya , a 

 number of species of Pennatulana, the sea stars Porcellanasteridae, the 

 Holothurioidea Elpidia , a number of species of the urchins 

 Pourtalesiidae, and many Pogonophora. 



Biocenoses of the lower bathyal and abyssal zones, interconnected 

 by gradual transitions with increasing depth, are quite characteristic 

 of the North Pacific. Let us analyze some of these biocenoses, located 

 in the open portion of the Gulf of Alaska and the waters of the North 

 Pacific. 



The biocenosis Onuphis pallida-Pavonaria pacifica-Ophiophthalamus 

 normani-Ophiura leptoctema is found in the upper and middle bathyal 

 region of the Gulf of Alaska. One of its groupings is: 



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