GHAiPTER 1. THE ESTUAEINE SYSTEM OF THE 

 UNITED STATES 



Man uses and is influenced by the whole world ocean, but that nar- 

 row zone where the land conttaining his civilization meets the sea is 

 unique. This is the point where man, the sea — his immeonorial ally and 

 adversary — and the land meet and challenge each other. That narrow 

 zone is the subject of this chapter ( IV-1-1 ) . 



The estuarine zone has many forms ; nearly all are represented along 

 the coastline of the United States. These include the classic drowned 

 river mouth, exemplified by Delaware Bay and in greater variety by 

 its neighbor, Chesapeake Bay. There are the entrance cuts and deltas 

 of great rivers such as the Columbia and the Mississippi ; there are the 

 marshlands of Georgia and the barrier island systems of North Caro- 

 lina. There are the coral formations of the Florida Keys and the fjords 

 of Alaska and Washington; there are the rocky coast of Maine, the 

 bluffs of California, and the sandy shores of Texas. There is infinite 

 variety but there is also the common theme of the sea, the land, and— 

 along much of the U.S. coastline — man. 



The estuarine zone of the United States was the gateway to a con- 

 tinent. The many deep, natural harbors of the Atlantic and the gulf 

 coasts provided safe anchorages for the ships which brought the first 

 colonists to these shores and which carried the produce of the land to 

 distant markets. The teeming coastal waters pro\dded a never- failing 

 supply of food to vary and supplement the results of farming and 

 hunting. 



The great population and industrial centers which developed around 

 these seaporte served as supply bases and takeoff points for those who 

 moved weist, north, and east to settle the enormous heartland of North 

 America, leaving the estuarine zone and its problems far behind, but 

 still using tliis zone to send their produce across the sea. 



This zone between land and sea is a unique environment deriving its 

 properties from both land and sea, but having characteristics resulting 

 from the existence of the interfacial zone itself and from the inter- 

 action of land and sea upon each other. 



SECTioisr 1. General Description 



The estuarine zone is best characterized as a region of constantly re- 

 curring change. The constanicy of change and the dynamic equilibriiun 

 associated with the changes comprise the visible features of the estua- 

 rine environment. The obvious complexity of structure, movement, 

 and life in the estuarine zone hides the inherently simply basic causes 

 of the existence and character of the estuarine environment. 



All life is dominated by gravity and by the sun's radiant energy, 

 but the effects of these are especially apparent in the estuarine zone. 

 The earth's gravity pulls the rivers down to the sea; at sea level the 

 gravitational attraction of the earth itself reaches a dynamic balance 



(62) 



