IV-440 



Changes in circulation associated with both spoil disposal and 

 manufactured residential islands in parts of Tampa Bay were followed 

 by changes in sedimentation patterns and an apparent decrease in 

 productivity in some areas (IV-6-4). 



Mining 



The taking of materials from the estuarine bottom immediately 

 destroys the local habitat and the movement and settling of suspended 

 material may extend the damage to other areas. Sand and gravel dredg- 

 ing are universal activities in the estuarine zone; oyster shell dredg- 

 ing exists in several areas along the Gulf and Atlantic coasts. 



Phosphate sand or rock mining in estuarine systems may raise the 

 concentration of phosphorus in the water and change the ecological 

 balance of the entire estuarine environment, as well as directly 

 killing fish and other aquatic organisms. 



Mining operations exploit a non-renewable resource, and even after 

 mining operations have ceased, the hole in the bottom of the estuary 

 may affect water circulation throughout the estuarine system. 



Flow Regulation 



The ecological balance of an estuarine system is the result of inter- 

 action of the dominating environmental factors discussed in Part IV., 

 Chapter 1. Among these factors are the amount and annual distribution 

 of fresh water inflow. Upstream flow regulation nay have many 



