THE BENTHAL 



177 



biotopes according to the nature of the shore, for example, pebble 

 beach, sand beach, mud beach, rock coast, coral coast, etc. 



In the pelagial, the lighted zone, which lies above the littoral, is 

 designated as the neritic province, and contrasted with the oceanic, 

 which lies over the greater depths and includes them. Special biotopes 

 in the pelagial are conditioned by the movements of the water, e.g., 

 regions of upwelling or sinking waters, currents, and quiet water. 



The benthal. — The primary difference between the life of the 

 benthal and that of the pelagial lies in the necessity for animals in 

 the latter to be independent of any support except that of the water. 



Benthal 



Pelagial 



200 



400 



^600 



Fig. 16.— Primary subdivisions of the marine habitat. After Pruvot. 



To be sure, an animal that is capable of remaining suspended in the 

 open water may also move or rest on the bottom. The bottom-dwelling 

 forms, however, are not able to float continuously, even though they 

 may be able to swim about, for a longer or shorter time, like the 

 pilgrim shell {Pecten jacobaeus) or like the fish called "stargazer" 

 (Uranoscopus) . The borderline between the animals of the pelagial 

 and benthal is thus not very sharp. If one emphasizes the characteristic 

 of free swimming too much, even fishes like the mackerel could be 

 regarded as only partially pelagic, since it is highly probable that they 

 rest from December to February on the sea bottom, after the strain of 

 continued swimming. Even though the same species of animal may at 

 some times be pelagic and at others littoral, the distinction between 

 the bottom fauna and that of the open water is none the less a natural 

 one. 



