IV-357 



may occur with the presence of other metals. For example, the toxic 

 effects of mercuric salts are accentuated by the presence of trace 

 amounts of copper. The table does indicate the minute quantities of 

 metal salts that can damage an estuarine system. 



INORGANIC NUTRIENT SALTS 



Aquatic life forms require trace amounts of some minerals 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 oversupply of 

 all necessary trace mineral salts and vitamins can retard growth or 

 stimulate it; 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. 



There may be shifts in population as the growth of one kind of life 

 is stimulated more than that of others by additional nutrients, 

 there may be increases in the general productivity of the entire 

 ecosystem, or there may be no changes at all if one necessary factor 

 is missing. When there is excessive growth with associated changes 

 in distribution patterns and predator-prey relationships, some 

 organisms may reach a state of "nuisance growths." This condition 

 is defined as a density of growth that interferes with a desirable 

 water use or the growth and reproduction of organisms desirable to 



