very short vegetation season (and, consequently, low productivity), as 

 in our own Siberian seas, the benthos has a eutrophic structure (A. P. 

 Kuznetsov, 1970). We should note yet another fact: In contast to the 

 abyssal area, where the oligotrophic structure of the benthos is 

 combined with very low content of organic matter in the bottom deposits 

 (Sokolova, 1969, 1972), on shelves with varying trophic structure of the 

 benthic population, no significant differences have been found in the 

 content of Cq^q in the bottom deposits (Gershanovich et al . , 1974). 



In the abyssal zone, the oligotrophic structure is combined with 

 deep transformations of organic matter (Bordovskiy, 1964). We did not 

 find analogous data for the shelves. However, since the oligotrophic 

 structure on the shelves was found only with a water temperature which 

 remained above 13°C throughout the year, and since the rate of 

 regeneration of biogenic elements increases by a factor of 10 as the 

 temperature rises from 5 to 30°C (Maksimova, 1974), we can assume that 

 with a high temperature, organic matter unsuitable for the nutrition of 

 detritophages, particularly swal lowers, is present in the bottom 

 deposits. It might be thought that the reason for the formation of the 

 oligotrophic structure of the benthos on the shelf is dual --either low 

 productivity of the shelf waters, or very rapid decomposition of organic 

 matter. In either case, the supply of the bottom deposits with organic 

 matter "edible" for detritophagous invertebrates would be reduced, 

 allowing us to retain the term "oligotrophic" for this structure. 

 However, the term does not have the same meaning as in the abyssal zone, 

 either in terms of the reasons of the oligotrophic formation or in terms 

 of the quantitative indices. 



We can draw the general conclusion that for shelves in the 

 temperate and cold zones, eutrophic structure is characteristic of the 

 benthos, while in warm waters, depending on the combination of a number 

 of factors, it may be eutrophic or oligotrophic. For example, along the 

 east coasts of the oceans, where zones of constant upwelling of water 

 are found, a benthos with an oligotrophic structure is rare, and is 

 encountered in limited areas. Along the west coasts of the oceans, 

 where the low-productivity central waters approach the coastline quite 

 closely, and in some places even extend onto the shelf, sections with 

 oligotrophic benthos structure are quite common. 



As we compare the peculiarities of the benthos of the shelves, 

 which are dependent on the mobility of the water and the particle-size 

 distribution of the bottom deposits, with the peculiarities which depend 

 on the supply of organic matter in the bottom deposits, we detect the 

 following regularities. 



1. On shelves with active dynamics of the bottom waters, 

 sestonophages predominate under all conditions. The influence of the 

 production processes and processes of regeneration of organic matter, 

 leading to an oligotrophic structure of the benthos, is hardly 

 noticeable. The trophic zonality characteristic for such shelves under 

 eutrophic conditions is fully retained. Only the occurrence of 

 detritophages, particularly swal lowers, changes. They disappear 

 completely from large areas of the shelf. 



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