lichens, apparently of the same species. Only two bands are clearly 



seen in the intertidal zone: the upper band, formed of 



Ulothrix austral is , and the lower band of diatoms, predominated by 



Melosira moniliformis . Kacrophytes appear only in the sublittoral 



(Delepine, Hureau, 1963). It is interesting to note that most genera of 



algae in the Antarctic intertidal zone Are the same as in the Subarctic 



regions. 



1.8 Sandy and Silty-Sandy Intertidal Zone 



In the qualitative aspect, loose soil beds ^re significantly more 

 sparsely populated than solid beds. The population of sandy beaches 

 exposed to surf is particularly sparse and homogeneous. Under Subarctic 

 conditions, the macrofauna is usually absent, although the meso- and 

 microfauna are rather widely varied. For beaches with surf in the 

 temperate and tropical zones, the most characteristic of the macrofauna 

 are the higher crustaceans: amphipods, isopods and, in the tropics, 

 crabs as well. Macrophytes are absent here, only microscopic algae 

 being present, rising to the surface of the sand for photosynthesis at 

 low tide and burying under the sand at high tide. As to composition of 

 fauna, three systems are usually distinguished on sandy beaches with 

 surf--the splash zone, or upper beach, which may be combined with the 

 supral ittoral edge of a rocky intertidal zone; the middle beach, 

 occupying a significant, sometimes predominant, portion of the 

 intertidal zone, and frequently poorest in life; the lower beach, in the 

 lowest portion of the intertidal zone. For the splash zone, the 

 amphipods Talitridae ( Orchestia , Talorchestia , Orchestoidea ) are 

 characteristic. In the tropics, the Ocypodidae predominate, 

 constructing deep burrows and running after the retreating waves with 

 surprising speed. In warm seas, right up to the lower boreal subzone, 

 isopods of the suborder Tyloidea ( Tylos and Helleria ) Are common. The 

 middle beach in the high boreal waters is quite poorly populated. Kost 

 characteristic d.re the sand hoppers ( Gammarus and Anisogainmarus ) , the 

 turbellarians, oligochaetes and nematodes. Primitive isopods of the 

 family Cirolanidae (Excirolana , Eurydice ) appear in the lower boreal 

 intertidal zone, and Are particularly characteristic for the tropics and 

 subtropics. Less common here Are the polychaetes Euzonus , Ophel ia , 

 Scolelepis , Nerine , Goniadides and others. The lower beach is usually 

 populated with a more varied and richer fauna, ("bst common here Are the 

 amphipods of the family Haustoriidae and Phoxocephal idae. For the 

 tropics, crabs of the family Hippidae (Emerita , Hippa , Arenaeus , etc.), 

 the bivalve mollusks Mesodesma , Amphidesma , Donax , the gastropods 

 Terebra , plus the crustaceans Sguilla and Callianassa are typical. For 

 both the wanii and temperate waters, the predaceous gastropods of the 

 family Naticidae, the bivalves Tivela , Tel 1 ina , Sil igua , polychaetes of 

 the family Nephthydidae, Glyceridae, Ariciidae and Opheliidae, mysids 

 and isopods of the family Cirolanidae Are characteristic. Many of these 

 species are found not so much in the lower intertidal zone as at the 

 water line, i.e., they form a migrating complex (mysids, many 

 Cirolanidae, Donax , some amphipods, shrimp, etc.). The biomass of 

 animals on sandy surf beaches is usually low, although in some places it 

 may be significant. 



157 



