identified and quantitated -- and the cost is high. The detection of any 

 given contaminant in the tissues of a species only proves that the chemical 

 is present. The biological significance of the contaminant or contaminants 

 in question must be determined by studying the organism and evaluating its 

 ability to function. 



Though much progress has been made in developing biological indicator 

 techniques, only the surface has been scratched. This is a ^jery promising 

 and exciting field of contaminant research but it may often be high risk and 

 time consuming. Nevertheless, the progress that has been made in "bioindica- 

 tor" research leads to the conclusion that it affords too great an opportun- 

 ity for the future to be neglected. Several bioindicator techniques that 

 show considerable promise are being tested or successfully used by fishery 

 and wildlife biologists and toxicologists (Mehrle and Mayer 1979). 



Bioindicator techniques are essentially used for two purposes. The 

 first is to monitor for the presence of contaminants, particularly when an 

 attempt is being made to locate point-source pollution such as may occur from 

 an industrial effluent. Mobile units can be used to draw water from suspect- 

 ed pollution source and expose test species for measurement of physiological 

 responses. Opercular rates (Sparks et al . 1972) and cough rates (Drummond 

 and Carlson 1977) have been used to monitor for the presence of contaminants 

 in industrial effluents. The second purpose, more meaningful from a popula- 

 tion viewpoint, is to measure biological or biochemical characteristics that 

 reflect whole-animal responses related to essential life processes (survival, 

 growth and development, reproduction, and adaptability) of the organism or 

 organisms in question (Mehrle and Mayer 1979). Eggshell thickness, for exam- 

 ple, has proved to be an excellent bioindicator related to reproductive 

 success in avian species subjected to high exposures of DDE (Klaas et al . 

 1974). Likewise, collagen composition in connective tissues, particularly in 

 the vertebrae, is a good indicator of inhibition of growth and development in 

 fishes exposed to contaminants (Mehrle and Mayer 1975). Other indices such 

 as behavioral patterns, biochemical imbalances, and incidences of teratogen- 

 esis or carcinogenesis may prove to be useful indicators of contaminant im- 

 pacts on wildlife populations. However, much research will be necessary to 

 test the usefulness and applicability of these approaches. 



SOME RESEARCH NEEDS 



Though many contaminant problems exist and many more are candidates for 

 future concern, scientists are limited in time, manpower, and financial re- 

 sources in their abilities to address them. A "shopping list" of contaminant 

 problems that are most likely to become serious threats to valued resources 

 can be formulated through communication with State and Federal resource man- 

 agers, regulatory agencies, industry, conservation groups, and research 

 scientists from government, academia, and industry. Some problems of con- 

 siderable concern have already been identified and should be addressed. 



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