IV-91 



SECTION 6. ENERGY AND MANAGEMENT 

 IN THE BIOPHYSICAL ENVIRONMENT 



Solar energy and gravitational energy are the basis for everything 

 that happens naturally in the estuarine zone. This discussion of 

 the biophysical environment has been concerned primarily with the 

 transformation of these energies into forms useful in living pro- 

 cesses and exploitable by man. Three different sets of subdivisions 

 of the biophysical environment were used in this discussion (Figure 

 IV. 1.39). 



Differences in the external environment divide the estuarine zone of 

 the United States naturally into ten geographic regions, each sub- 

 ject to a particular combination of the external influences of tide, 

 ocean currents, wave action, sedimentation, and climate. This sub- 

 division into estuarine biophysical regions gave broad ranges of con- 

 ditions in each region, but the importance of local coastal condi- 

 tions in determining energy flows via water movement paved the way 

 for a subdivision of the estuarine zone according to 11 morphologi- 

 cal groups having similarities in water movement, circulation, and 

 the ability to rid themselves of wastes. 



A subdivision according to ecological communities is also based pri- 

 marily on geographical location, but again local coastal conditions 

 make it necessary to identify small ecosystems within each major 

 grouping. This subdivision rests not only on the shaoe and form of 

 coastal areas, but also on the composition of the estuarine bottom. 



