VI-127 



SECTION 5. TOXICITY 



All too often data required to Interpret toxic conditions are obtained 

 solely through field observations after the environment has been 

 irreversibly changed and an ecological catastrophe has occurred. 

 Predictions and management decisions based on this kind of informa- 

 tion are poor at best. The only way that the knowledge needed by 

 managers to cope with potentially toxic situations can be available 

 in time to be useful is by having previously established tolerable 

 levels of pollutants, developed through bioassay techniques, and 

 appropriately extrapolated to natural conditions. Toxicity studies 

 would be concerned not simply with levels at which a soecies could 

 survive, but also at what levels it will reproduce to complete its 

 life cycle without significant change. From such studies, criteria 

 could be established much as they are for public health measures, 

 but relevant to the organisms as well as to man. Only through such 

 long-range programs can the desirable biologically productive aspects 

 i| of estuaries be preserved and the other beneficial uses augmented. 



SUBLETHAL EFFECTS 



There is a growing awareness that, in the long term, the major con- 

 cern should be for an understanding of sublethal chronic effects in 

 order that realistic water quality criteria may be developed based 

 upon the interrelationships within ecological systems. Much of the 

 presently available data have been derived from acute toxicity tests 

 on adults without adequate consideration of the chronic effects 



