VI-131 



laboratory are certainly not confronted with the complex Inter- 

 acting factors which occur 1n the natural environment. Under 

 natural conditions, there may be a rapid reduction 1n the concen- 

 tration of a toxicant by precipitation, adsorption on soils and 

 bottom materials, chemical decomposition, reactions with other 

 substances In the water, absorption by microscopic organisms, 

 removal by organisms, or biochemical degradation. Accumulation 

 of toxicants in the food chain and ingestion of food organisms 

 bearing relatively high concentration of these materials may 

 Increase the exposure to higher animals. 



Laboratory findings on the safe levels of potential toxicants 

 must be field tested under conditions wherein the organisms in 

 question are exposed to all stresses occurring in the natural 

 environment. When developed, tested, and evaluated, field studies 

 can be used for simultaneously testing the entire community under 

 natural conditions. Such studies Integrate the effects of biological 

 magnification; storage; passage through the food chain, accumulation 

 in bottom materials, competition for food, cover, and living space; 

 disease, oarasites, and predators; synergism, antagonism, and the 

 Interaction of materials; and all other complicating factors present 

 in the natural environment. 



To be a truly useful management tool, a catalog should be developed 

 indicating the tolerance levels of plant, animal, and bacterial 

 estuarine species for the pollutants so commonly found in the 



