IV-4 



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

 continent. 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 

 provided 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 seaports served as supply bases and take-off points 

 for those who moved west, north, and east to settle the enormous 

 heartland of North America, leaving the estuarine zone and its 

 problems far behind, but still using this 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. 



