CHAPTER III. BENTHIC COMMUNITIES AND THEIR 

 STRUCTURAL AND FUNCTIONAL CHARACTERISTICS 



1. Littoral Communities . (0. G. Kussakin) 



The boundary of the ocean is generally considered to be the line of 

 zero depth, representing the lowest possible tide for a given area 

 resulting from purely astronomic causes. However, the influence of the 

 ocean is wery strongly felt along the shore at points located slightly 

 higher than the zero depth line. Therefore, the intertidal zone and 

 supralittoral areas, although they are located above the zero level, i.e., 

 formally belong to the land, are considered zones of the sea. 



The intertidal zone, or drying zone, is defined as the zone located 

 between the high and low tide marks. Thus, its lower boundary is the 

 zero depth level, and its upper boundary is the highest theoretically 

 possible tidal level. Consequently, the intertidal zone is a zone which is 

 periodically flooded with water, and periodically exposed, subjected to 

 the action of the air. The amphibiotic nature is its most characteristic 

 feature. Although its vertical extent is extremely small (from a few 

 centimeters to 16 m in the Bay of Fundy), if the shoreline has a gentle 

 slope the width of the intertidal zone may be as much as several kilometers. 

 No matter what the width of the intertidal zone, the degree to which it 

 is amphibiotic changes a great deal from its top to its bottom; therefore, 

 the conditions for the life of littoral organisms change a great deal over 

 a small distance. In spite of the fact that the intertidal zone is a 

 zone which is transitional between the land and the sea, the overwhelming 

 majority of its population consists of marine plants and animals, although 

 in certain places, particularly those protected from the surf, specialized 

 forms of land organisms predominate--marsh halophytes and mangroves. 



Its boundary position between the two main habitats of life--the 

 air and the water--and the amphibiotic conditions present there distinguish 

 the intertidal zone among all other zones of the sea. The daily and 

 seasonal fluctuations in temperature, salinity, moisture content, etc., 

 are most sharply reflected here. Great expanses of the coastline in 

 the Antarctic, Arctic and temperate latitudes are covered in winter 

 with ice which, on the one hand, has a destructive, abrasive influence, 

 but on the other hand, protects the inhabitants of the intertidal zone 

 from the effects of the extremely low air temperatures. 



Above the intertidal zone is the supralittoral zone, which is also 

 subject to the influence of the ocean, though to a lesser extent. This 

 zone is flooded with water only sporadically, during strong onshore winds 

 or severe storms. The rest of the time, the supralittoral is irregularly 



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