characteristic for other seas in the Arctic as well. The Baltic Sea, in 

 which detritophages sharply predominate, is of this same type (A. P. 

 Kuznetsov, 1963, 1964, 1970, 1974). Shelves of type 3 are shelves on 

 which, depending on their width and steepness, the direction of 

 prevailing currents and the distribution of benthic deposits, we find 

 the corresponding development of zones of predominance of all three 

 trophic groupings. 



Trophic zones which depend on the sedimentation mode are 

 distributed just a regularly as zones of erosion and accumulation of 

 sediments. M. N. Sokolova (1960) showed, using the example of the 

 northwest Pacific, that they most frequently alternate vertically, 

 following the bottom relief. On convexities of the bathymetric curve, 

 zones of predominance of sestonophages usually develop; in concavities-- 

 zones of predominance of gatherers, and deeper--swal lowing 

 detritophages. On the next, deeper, convexity, a zone of predominance 

 of sestonophages appears once more, etc. Thus, a set of three trophic 

 zones is placed vertically one above the other. 



Shelves differ as to width and steepness (Fig. 10). On all 

 shelves, the shallows are occupied by sandy or rocky soils, allowing the 

 development of zones of sestonophages (mobile or attached) in these 

 areas. Deeper, depending on the width and steepness of the shelf, a 

 zone of sedimentation is developed to some extent (Gershanovich et al . , 

 1974) with predominance of gathering or swallowing detritophages. It 

 may occupy various areas of the bottom, the predominance of 

 detritophages may be expressed to varying degrees--from slight 

 domination (40-50% of the total biomass) to complete domination (over 

 95%). One regularity is found which has not at present been fully 

 explained. On broad shelves with a well -developed zone of 

 sedimentation, the finest clayey silts are dominated by collecting 

 detritophages, while swallowing detritophages predominate on somewhat 

 coarser silts. On narrower shelves, where the zone of sedimentation is 

 not so broad, the very finest silts are dominated, not by collecting, 

 but rather by swallowing, detritophages (A. P. Kuznetsov, 1963; Neyman, 

 1963a). 



As a rule, the vertical trophic zonality is expressed rather fully 

 on shelves, which is facilitated by the currents directed along the 

 edges of the shelf. Sometimes, the influence of the relief on the 

 distribution of trohic zones may be buried by that of other factors. 

 For example, if the currents are directed across the shelf, the vertical 

 trophic zonality may be distorted, to the point of appearance of 

 spottiness in the distribution of trophic zones (A. P. Kuznetsov, 

 1970). However, the relationship of distribution of trophic zones with 

 the mode of sediment accumulation is fully preserved--in these cases, 

 the zones of erosion and sedimentation are also distributed in spots 

 (Sokolova, Neyman, 1966). 



All of these conclusions were reached in a study of the benthos of 

 shelves located under subarctic waters. Upon transition to a stuciy of 

 subtropical and tropical shelves, cases were noted which did not fall 

 within the system described above. Here, the concept of eutrophic and 

 oligotrophic types of trophic structures suggested by M. N. Sokolova 



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