Schemes like the scheme of the Stephensons, which combine the 

 characteristic features of vertical stratification of the basic communi- 

 ties, can be used only in comparative ecologic studies, always in com- 

 bination with subdivision of the intertidal zone according to the principles 

 of Vaillant. 



Of course, when used in this manner, the terminology of the Stephensons 

 must be slightly altered, since the "zones" of the Stephensons--the 

 supral ittoral edge, the middle littoral zone and the sublittoral edge--are 

 not considered by us to be the primary subdivisions of the intertidal zone, 

 but only characteristic types of formations of rocky facies of the 

 intertidal zone. We consider it expedient to call them systems or divisions. 

 Since the term "middle littoral zone" might be easily confused with the 

 middle, or second, horizon in the system of Vaillant, we propose to apply 

 the term "true intertidal zone" or "true littoral division" (eul ittoral) 

 to this division. 



In nontidal seas, like the Black Sea and Baltic Sea, where there is 

 no true (tidal) intertidal zone, there are communities quite similar to 

 littoral communities, though their vertical stratification is much less 

 fully developed. In these seas, there is a special zone, which has come 

 to be called the pseudol ittoral , which owes its existence to the surf waves 

 (Mokiyevskiy, 1949). 0. B. Mokiyevskiy accepts the upper edge of the 

 maximum surf spread as its upper boundary, the lower edge of the beach, 

 where the surf wave is obstructed, as its lower boundary. 



1 .2 Factors Specific for the Littoral 



The nature of the connection between the sea coast and the ocean or 

 open sea has a great influence both on the abiotic conditions of the littoral 

 environment, and on its population. Open, unprotected shores are usually 

 subject to strong surf action, the surf becoming weaker with increasing 

 distance from the ocean, and practically disappearing in partially closed 

 bays and lagoons. The role of the surf in the conditions of the intertidal 

 zone is very significant and quite varied. First of all the surf, wetting 

 the intertidal zone partially neutralizes the effect of the tidal factor, 

 particularly at low tide. This decrease in amphibiotic conditions in the 

 intertidal zone under the influence of the surf means that as the force and 

 constancy of the surf increase, the vertical stratification of littoral 

 communities becomes decreasingly tied to the tidal levels, since in surf 

 areas they extend higher up the shore than in protected areas. In areas 

 with strong surf, this upward shift may reach 2-6 m (Burrows et al . , 1954; 

 Kussakin, 1961 •, Vozzhinskaya , 1955). Also, as a wave breaks and the 

 layers of water are mixed, the water is enriched with oxygen, frequently 

 to the point of supersaturation. This encourages the existence of many 

 oxyphilic animals in areas where there is surf. 



However, the surf also has a harmful mechanical effect, washing away 

 organisms which are not tightly attached. In loose sediments, the surf 

 helps to wash organic matter out of the sediment and causes motion of 

 sediment particles. Therefore, on beaches with surf, even though the 

 oxygen mode is favorable, the food value of the sediment is frequently low. 



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