1 1-3 



is accomplished by an intricate array of prey--predator relationships 

 among living organisms, from the microscopic living creatures which 

 convert solar energy directly and are eaten by other organisms, to 

 the fish and wildlife which are the ultimate life forms in the manless 

 estuarine environment. 



Solar radiation and gravitational forces control the natural environ- 

 ment through a complex series of mechanisms. In the estuarine zone 

 this control exhibits itself through seven major environmental factors 

 that exist throughout the estuarine zone. 



(1) Continental Shelf . The submerged land next to the 

 continent slopes gently to a depth of about ^no feet, then 

 it drops more rapidly to form the deep ocean basins. This 

 fringe of slightly sloping submerged land, which along 

 much of the Atlantic and Gulf coasts would appear quite 

 flat to the naked eye, is called the "continental shelf;" 

 its width and general configuration along the U. S. coast- 

 line affects the force with which ocean waves strike the 

 shore and consequently the manner and deqree of shoreline 

 erosion and accretion (Fiqure IV. 1.1). 



(2) Ocean Currents . The major ocean currents passing 

 near or impinginq on the continent exert strong, if 

 subtle, effects on the estuarine zone through their 

 temperatures, which affect continental land temperatures, 



