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the biophysical environment were used in this discussion. 



Differences in the external environment divided the estuarine zone 

 of the United States naturally into ten geographic regions, each 

 subject to a particular governing combination of the external 

 influences of tide, ocean currents, wave action, sedimentation, 

 and climate. This subdivision into estuarine biophysical regions 

 gave broad ranges of conditions in each region, but the importance 

 of local coastal conditions in governing energy flows via water 

 movement paved the way for a subdivision of the estuarine zone 

 according to ten morphological groups having similarities in water 

 movement, circulation, and the ability to rid themselves of wastes. 



A subdivision according to ecological communities was also based 

 primarily on geographical location, but again coastal conditions 

 made it necessary to identify small ecosystems governed by 

 specific local conditions within each of the major groupings. 



