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the exchanges which occur between the estuarine waters and offshore 

 waters, the influx of freshwater and other drainage from the land; 

 between the water mass and the bottom sediments; and between the 

 water mass and the atmosphere. Another area of interface concern, 

 the movement of materials between the biological compartment and 

 the aquatic compartments of the estuary, is the major theme of much 

 of this chapter and hence will not be discussed here. 



Land Drainage-Estuary-Sea Interface 



Because the. estuary itself is the interface between the sea and 

 the land, the ocean-estuary interface and the estuary-land drainage 

 interface are complimentary in many ways. The alteration of either 

 one is reflected in the change in effect of the other. In some 

 cases the estuary is a gradual continum from fresh to sea water; 

 in others the lines of demarcation are abrupt and well-defined. 

 The most obvious physical demarcations of land drainaqe-estuary- 

 sea are based on salinity, thus, the discussion of these two inter- 

 faces is combined. 



It is established that various biological life is dependent on 

 salinity gradients throughout the estuarine zone. For example, the 

 high value of the Gulf Coast shrimp industry is dependent on the 

 bays as nursery grounds; however, the amounts and quality of fresh 

 water required to support the ecological system of each individual 

 bay has not yet been established. This is a Dressing research need. 



