248 



tion phenomenon has been documented with such pollutants as pesti- 

 cides, heavy metals, and radionuclides. The body concentration of the 

 toxicant may reach such a level that death results in the host organism 

 when the material is released to the blood stream by physiological 

 activity. Any higher carnivore consuming an organism with high tis- 

 sue concentrations of toxic materials maj be subject to acute or fatal 

 poisoning. Table IV.5.2 lists the biological magnification factors of 

 five moUusks for specific pesticides (IV-5-2) . 



The pesticide group is of particular concern in the estuarine zone. 

 Estuaries are the terminus for most of the major river systems, and 

 as such they tend to concentrate the waterborne 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. Table IV.5.3 shows 

 the concentration of selected pesticides that will kill 50 percent of 

 exposed shrimp within 48 hours. Shrimp are one of the most sensitive 

 groups of marine organisms (IV-5-1 ) . 



TABLE IV.5.2— MAGNIFICATION FACTORS OF FIVE SELECTED MOLLUSKS i 



Magnification 

 Pesticide: f«"8e 



Lindane 10- 250 



Endrin 500-1, 250 



Methoxychlor 300-1, 500 



Dieldrin 700-1, 500 



Heptachlor 250-2, 500 



Aldrin 350-4, 500 



DDT... 1, 200-9, 000 



1 Mention of any trade name in this report does not constitute endorsement of the product by the Federal Government. 



TABLE IV.5.3.— THE 48-HOUR TLm' FOR SHRIMP FOR SELECTED PESTICIDES (IN MICR06RAMS/LITER) 



■ TLm=concentratlon which will kill 50 percent of exposed animals. 



Many other materials have a toxic effect on estuarine biota. These 

 materials may be present in various industrial wastes or be byproducts 

 of interaction within the estuary. Examples are cyanides from metal- 

 plating wastes and sulfides from the anaerobic decomposition of 

 sewages and industrial wastes. 



Wastes from the chemical industry are highly variable and poten- 

 tially toxic. Ever-changing chemical technology leads to many new 

 products, each creating a new, complex, waste-disposal problem. 



Included in the consideration of toxic materials are radionuclides 

 discharged to the estuarine waters. Ionizing radiation, when absorbed 



