Intertidal Environment (Littoral) 



143 





Figure 125. Bank of tidal channel in marsh at Mission Bay near San Diego showing mud deposited around rhizomes 

 of Salicornia and bored by a crab [probably Uca crenulata (Lockington)] so thoroughly that slumping occurred. Photo- 

 graphed in February 1944. 



algae and plankton washed ashore and 

 buried in the sand. Animals of the beach 

 are almost exclusively those that are able to 

 bore into sand rapidly. 



Among the few species living on beaches 

 are the sand hopper, an amphipod Orches- 

 toidea californiana, which expels sand from 

 its burrow with such force that colonies are 

 marked by a criss-crossing pattern of stripes 

 of fresh sand a foot or so long (Emery, 

 1944). The sand crab, Emerita analoga, 

 oval and about 2 cm long (Fig. 126), may be 

 seen in large numbers washing up on the 

 beach on the swash ahead of the tide and 

 busily digging into the sand until only eyes 



and antennae are left projecting to catch 

 fine organic debris washed across the sand 

 by the swash. Usually present on sand 

 beaches are the separate valves of a flat 2.5- 

 cm-long clam, Donax gouldii. Living speci- 

 mens are usually extremely rare because the 

 clam flourishes only at intervals of several 

 years, there having been seven major re- 

 surgences between 1895 and 1950 (Coe, 

 1955). Another, the Pismo clam, Tivela 

 stultorum, is heavy-shelled and prefers the 

 surf zone. Because of its food value this 

 clam is in danger of extermination in south- 

 ern California, although formerly it was 

 very abundant according to Ricketts and 



Figure 126. Some important 

 inhabitants of sand beaches in 

 southern California: A, Tivela 

 stultorum (Mawe), Pismo clam 

 (XO.25); B, Donax gouldii Dall, 

 bean clam (xO.7); C, Orches- 

 toidea californiana (Brandt), 

 sand hopper (xl.2); D, Eme- 

 rita analoga (Stimpson), sand 

 crab (xO.7). 



