On the other hand, an ice cover, particularly where it remains 

 almost immobile throughout the winter, isolates the inhabitants of the 

 intertidal zone from the effects of the \/ery low air temperatures during 

 low tides, and the harmful effects of winter storms. This positive 

 influence of ice cover allows many warm-water species to tolerate severe 

 winter conditions and is, along with the great warming in the summer, 

 one of the main reasons for concentration of thermophilic faunal and 

 floral elements in areas protected from the surf. 



Climatic conditions also have a great influence on the intertidal 

 zone. A mild oceanic climate with slight seasonal and diurnal variations 

 in air temperature, cool, wet summers with abundant fog and moderate 

 winters are most favorable for the inhabitants of the intertidal zone. In 

 regions with this type of climate--the Komandorskie Islands, Kerguelen 

 or Macquarie--the intertidal zone is richly populated (Gurjanova, 1935; 

 Ushakov, 1958), since many sublittoral species rise into the intertidal 

 zone. Conversely, in areas with hot, dry summers or cold, long winters, 

 the littoral communities are usually sparse, particularly multiannual 

 algae, which cannot leave the intertidal zone during the unfavorable 

 seasons. Therefore, in the tropics, the algoflora has a tendency to 

 shift downward to the lower horizons of the intertidal zone or into the 

 sublittoral (Gurjanova, 1961a; Mokiyevskiy, 1964, 1967). 



The time of day at which low tide occurs is of great significance, 

 particularly in countries with hot, dry seasons (Stephenson, Stephenson, 

 1972). For example, in the intertidal zone of Ghana in the summer the low 

 tides occur at night, and as a result, regular penetration of certain 

 mass species of algae into higher horizons is observed. In the winter, 

 the lowest tides are observed in the day, resulting in a lowering of the 

 upper boundary of a number of algae (Lawson, 1957, 1956). If fog is 

 frequent during low tide, this has a favorable influence on the littoral 

 biotope. The orientation of the coast is also important, as it determines 

 exposure to sunlight, as is the steepness of the shore. Southern exposures 

 and gentle slopes are more strongly subject to the drying influence of 

 the sun than are northern or steep (i.e., shaded) shores. In countries 

 with monsoon climates, strong rains may cause the death of many littoral 

 organisms if they occur at low tide. 



1 .3 Typology of Intertidal Zones 



In our opinion, the most convenient and acceptable classification of 

 intertidal zones is that based on bionomic types developed by E. F. 

 Gurjanova, I. G. Zachs and P. V. Ushakov (1930a, b). Following the prin- 

 ciples which they developed, we can distinguish six bionomic types of 

 intertidal zones. 



First bionomic type (moderately protected shore). Characterized by 

 second or third degree surf. Good aeration, salinity usually high, 

 but may be lower near rivers. Distinguished by the greatest richness 

 and variety of littoral communities, the vertical stratification of 



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