Of the many attempts which have been made to classify pools, the 

 classification of T. Gislen (1930) seems most suitable to us. This 

 classification divides them into sublittoral, intertidal zone, and 

 supralittoral types. Sublittoral pools are usually located in the lov;er 

 horizon of intertidal zones and are usually washed by waves and surf or 

 are connected with the sea by narrow channels. Their population is 

 basically similar to the sublittoral population. Littoral pools are 

 connected with the sea during high tide or when wave action is strong. 

 The changes in temperature and salinity in these pools are significantly 

 greater than in the sea. Their population is usually quite varied; in 

 addition to typical sublittoral and littoral species, forms are also 

 seen which are found only in pools. Supralittoral pools are connected with 

 the sea only during maximum high tide, and sea water enters these pools 

 only in the form of surf spray and storm waves. After strong rains, the 

 water is sometimes almost entirely fresh, while during hot weather, con- 

 versely, the salinity may be higher than that of the sea. The temperature 

 fluctuations are also quite great. The fauna and flora of these pools 

 includes a few eurybiotic marine representatives, plus a specific popu- 

 lation made up of brackish-water and even fresh-water, frequently ephemeral, 

 species. 



Pools are found in all of the other bionomic types of intertidal 

 zones; therefore, many authors do not distinguish them as a specific 

 bionomic type, but rather consider them specific habitats (Newell, 1972) 

 or as separate biotopes (Zhyubikas, 1969) within each of the remaining 

 bionomic types. 



1 .4 General Characteristics of the Littoral Biota of the 

 World Ocean 



We noted earlier that in all climatic zones and on all sediments, 

 clear vertical stratification of organisms is a characteristic of the 

 intertidal zone. On relatively unbroken, morphologically homogeneous 

 shores, the communities are located in bands, strips frequently extending 

 over great distances, but always relatively narrow. They can be easily 

 distinguished on a rocky shore, and are less clearly seen, but still well 

 expressed, on shores consisting of loose sediment. This type of distribution 

 is called linear, or banded. 



Some believe (Gislen, 1943; Gurjanova, 1947, 1959, 1961a) that the 

 banded distribution of groups (communities) is primarily characteristic 

 for the intertidal zone in the temperate and higher latitudes, with a 

 mosaic distribution predominating in the lower latitudes. This is explained 

 by the more acute interspecies competition in the tropical intertidal 

 zone, a result of the increased number of species attempting to populate 

 a single level or sublevel (Gurjanova, 1961a). Nevertheless, even in the 

 tropics, the banded (linear) distribution of littoral communities is quite 

 common. On the other hand, even in the temperate zones, where the 

 morphology of the shore is complex, a number of "inserted," supplementary 

 communities appear, and the banded distribution is replaced by a spotty 

 or mosaic distribution. 



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