31 



stances within their cell structure, the presence of these metals in small 

 concentrations can have deleterious effects. 



Aquatic life forms require trace amounts of some mmerals and 

 vitamins for growth and reproduction. Elimination of such materials 

 from the environment or their reduction below minimum levels can 

 limit the growth and reproduction of some biota. Conversely, an over- 

 supply of all necessary trace mineral salts and vitamins can stimulate 

 growth, providing satisfactory conditions of temperature, salinity, 

 and dissolved oxygen also exist. An oversupply of inorganic nutrient 

 salts, such as those of nitrogen and phosphorus, may be associated with 

 drastic shifts in the composition of the aquatic community. 



One of the many unfavorable effects of municipal and some in- 

 dustrial wastes is the contamination of the receiving environment with 

 bacteria, viruses, and other organisms of public health significance. 

 Pathogenic organisms^ especially those from the intestines of warm- 

 blooded animals frequently persist for sufficient periods of time and 

 distance to pose a threat to the health and well bemg of unsuspecting 

 water users. Secondary chances of exposure to these organisms exist 

 through the contamination of shellfish which can be harvested for 

 food. 



Among the waste products that are frequently introduced into the 

 estuarine environment are some directly toxic to marine organisms. 

 Toxic materials may exhibit a short catastrophic impact or a more 

 subtle long-term interference with growth and reproduction proc- 

 esses. The end result is to create a biological desert in which no organism 

 can survive. The pesticide group is of particular concern in the estua- 

 rine zone. Estuaries are the terminus for most of the major river sys- 

 tems, and as such they tend to concentrate the waterbone materials 

 carried in by the large terrestrial drainage systems. The biological 

 magnification capability of estuarine animals significantly increases 

 the hazard and destructive potential of any contributed pesticides. 

 The ultimate damage is to stress or eliminate parts of the energy con- 

 version chain in the estuarine environment. 



The addition of large quantities of heat from industrial cooling 

 water constitutes a form of pollution which must be considered. The 

 entire ecosystem may be stressed by thermal pollution. The amount of 

 damage is dependent on the resulting temperature of the environment 

 and the species composition of the biotic community. The total range 

 of detriments should be carefully considered on an individual case 

 basis before heat is released to the environment. Heat affects the physi- 

 cal properties of water, the rates at which chemical and biological re- 

 actions progress, and can kill living organisms. 



Man's activities may affect the rate of sediment inflow, deposition, 

 and outflow by purposely or inadvertently upsetting the natural bal- 

 ance. If upstream erosion is increased due to poor land management 

 practices, the load carried in will increase. Conversely, activities along 

 the coast can result in increased shore erosion, removing more sediment 

 than is contributed. The primary pollutional problem from sediment, 

 however, is from increased influx and accelerated deposition. The det- 

 rimental effects of sedimentation are reflected in an impairment of 

 uses such as navigation, recreation, and fish propagation. 



One of the greatest threats to the estuarine ecosystem is the ever- 



