Shelf Environment (Sublittoral) 



imity to Point Conception, which has served 

 for a long time as a supposed southern hmit 

 for many intertidal species. In contrast, the 

 shelf south of Oceanside has a fauna of 

 southern origin, many animals continuing 

 southward to their areas of main concentra- 

 tion off Baja California. They therefore ig- 

 nore the United States-Mexican boundary 

 Hne which is frequently mentioned in the 



165 



literature as the southern limit of many inter- 

 tidal species. 



Throughout the mainland shelf most of 

 the species are of polychaete worms and 

 amphipod crustaceans, averaging 42 and 36 

 per cent, respectively (Fig. 144). Similarly, 

 most of the individuals are polychaetes and 

 small crustaceans, averaging 42 and 38 per 

 cent, respectively. Echinoderms and small 



Figure 142. Forest of kelps {Macrocystis pyrifera) off Los Coronados Islands rising from the ocean floor about 25 

 meters upward to the water surface. Blades are about 30 cm long. Note the holdfast that has become dislodged from 

 the bottom and is being floated away. U. S. Navy photograph by R. F. Dill. 



