EXTREME 



HIGH WATER 

 SPRING 



PHYSICAL 



INTERTIDAL 



ZONE 



EXTREME 

 LOW WATER 

 SPRING 



LJTT0B«:;:2£)MB 



(/vJWHNT.ERTlOAt SUBSYSTEMS 



^SUBLlTTORiAriL,. .;Z.QNE ; 



:j(t5!M^jOTMl^y3^|S^ 



PROTECTED AREA 



-INCREASING EXPOSURE- 



EXPOSED AREA' 



Figure 4-20. 



Comparison of the boundaries of the physical intertidal and 

 subtidal zones and the littoral (biological intertidal) and 

 sublittoral (biological subtidal) zone with increasing exposure 



to wave action 



(ada'pted fro~i "^^ew'-S l*^?':) 



area for these regions would be even larger than the southwestern regions if 

 the area out to the 300-foot (100-m) contour were calculated. Regions 1, 2, 

 and 3 have 13,730 acres (5559 ha; 12%), 2323 acres (940 ha; 2%), and 988 acres 

 (400 ha; 1%) respectively. The total subtidal area in the characterization 

 area is 112,120 acres (45,393 ha). The western regions also were not 

 calculated to the 300-foot contour but the difference between the actual and 

 calculated subtidal acreages in the western regions is not as large as that in 

 the eastern regions . 



The relative stability of the subtidal environment allows for the 

 establishment of diverse, highly organized communities. In general, physical 

 stability and biological diversity increase with depth (Gray 1974) . The 

 effects of seasons, waves, and currents, are felt less with increasing depth; 

 therefore, communities are less vulnerable to physical disturbances. The 

 principal physical factors that affect subtidal benthos are water temperature 

 and temperature range, substratum type, salinity, and water currents. 

 Phytoplankton, most zooplankton, pelagic fishes and many marine mammals spend 

 most, if not all, of their lives within the water column. The bottom is 

 occupied by benthic invertebrates and demersal fish and, in shallow water, 

 macroalgal species, which are important producers. Marine birds utilize the 

 surface or near-surface marine subtidal waters for feeding, molting (i.e., 

 eider ducks), and resting. 



4-60 



