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ECOLOGICAL FACTORS: 



animals, need not be specialized as land organisms 

 are. 



MARINE FACTORS 



Certain ecological factors often have more influence 

 on sea rather than land creatures. Ocean currents 

 change water temperatures and salinity, distribute 

 plant and animal nutrients, and disperse the larvae 

 of sedentary animals. Tides seem to have no effect 

 upon open sea organisms, but are associated with the 

 various adaptations of intertidal animals (those be- 

 tween highest and lowest tide levels) to temperature 

 and salinity changes and drying. The greater the 

 surf action, the more plants and animals found with 

 specialized attachment devices. Salinity tends to be a 

 very stable thing except when associated with other 

 factors. Although some animals, especially bay, 

 estuary, and tidepool species, can withstand gradual 

 salinity changes, only a few can survive rapid, great 

 changes in salinity. 



In intertidal areas many marine organisms are at 

 different and characteristic depths along the shore. 

 The most important local factors thought to bring 

 about this intertidal distribution of plants and ani- 

 mals are wave shock, substrate, and exposure. Wave 

 shock naturally varies from harbor swells to waves of 

 large proportions (20 feet or more). The primary 

 types of substrate are sand, mud, and large to 

 gigantic boulders, or even rocks integrated into 

 their geological formation. 



EW 



shoals 



Figure 17.6 Intertidal tiabitots: SOC, sandy outer coast; ROC, rocky 

 outer coast; PSOC, protected sandy outer coast; PROG, protected rocky 

 outer coast; EW, exposed wtiort; PW, protected wharf; B & E, bay and 

 estuary with subdivisions of mudflats, sandflots, eelgross, and rocky 

 shores. 



INTERTIDAL HABITATS 



The major intertidal habitats, diagnosed primarily 

 by amount of wave shock, are Protected Outer Coast, 

 Open Coast, Bay and Estuary, and Wharf Piling. 

 The subdivisions of these habitats are based upon 

 exposure and substrate. 



On the basis of wave shock alone, the following 

 intertidal habitats can be recognized (Figure 17.6): 



Profected Outer Coasi. This habitat includes semi- 

 sheltered coasts, open bays, and other areas protected 

 from the full force of ocean waves. Protected areas 

 can exist as a result of offshore reefs, kelp beds, 

 islands, or even gradual sloping shore bottoms. 

 There are two subdivisions of this habitat. Rocky 

 Shores and Sandy Beaches. These particular Rocky 

 Shores maintain more life than any other intertidal 

 habitat. Every available place is likely to be used by 



organisms. Common animals are crabs, chitons, 

 brittle stars, and sea anemones. Protected Outer 

 Coast Sandy Beaches have fewer organisms than 

 any other intertidal habitat. Part of this is the result 

 of the limited extent of this habitat. The main or- 

 ganisms found are scuds and segmented worms. 



Open Coasf. This completely unprotected habitat 

 has fewer organisms than the Protected Outer 

 Coast. Open Coast species either require or tolerate 

 the most violent surf action. The subdivisions found 

 in the Protected Outer Coast are found here as well. 

 Along Rocky Shores are animals with remarkable re- 

 sistance to wave shock and capabilities of attach- 

 ment. The most characteristic animals are goose- 

 necked barnacles and mussels. The Sandy Beaches 

 have certain crabs, and clams. All of these animals 

 burrow, probably to resist wave action. 



