other research being conducted that involves short-cut methods to 

 chronic toxicity studies has been highlighted by the U.S. Environmental Pro- 

 tection Agency's Environmental Research Laboratory-Duluth (1977-1979) and 

 includes the following advances: 



1. Measurement of ventilatory patterns of fish with a microcomputer 

 monitoring system. 



2. Use of fish cough frequency as an estimate of chronic toxicity. 



3. Development of a rapid toxicity test in which the fingernail 

 clam is used. 



4. Monitoring liver aryl hydrocarbon hydroxylase induction in fish. 



5. Changes in steroid hormone metabolism in fish. 



6. Saltwater tolerance and smoltif ication in salmon. 



Aquatic Plants 



The effect of point and non-point source contaminants on submersed 

 rooted vegetation is little known. The contribution of submersed rooted 

 aquatic macrophytes to the ecological support of fishery and wildlife re- 

 sources can be separated into three general categories: 



1. Numerous species of mammals and waterfowl are directly depend- 

 ent on macrophytes as food. For example, the stems, leaves, 

 seeds, and rootstock of sago pondweed constitute up to 50 per- 

 cent of the diet of migratory ducks and geese. Submersed rooted 

 macrophytes are also required by fish for forage, cover, and 

 spawning; furthermore, they provide an important substratum for 

 invertebrates eaten by fish. 



2. The overall metabolism of aquatic systems (lakes and streams) 

 supporting fisheries is dependent to a major extent on the 

 detritus components of dead, dissolved, and particulate organic 

 carbon which form the primary source of biological energy. 

 Beds of submersed, littoral, rooted macrophytes contribute a 

 large part of the organic detritus in all but a few aquatic 

 systems. 



3. Littoral vegetation also modulates the flow of inorganic nutri- 

 ents from the watershed to the limnetic area and stabilizes and 

 controls the magnitude of planktonic photosynthesis in lakes. 



In addition, contaminants deposited in bottom muds may be taken up by 

 plants and passed along a detrital food chain, ultimately to fish, water- 

 fowl, and other organisms closely associated with aquatic ecosystems. To 

 estimate the effects of contaminants on rooted aquatic vegetation, we are 

 examining the following variables for inclusion in chronic laboratory tests 

 with appropriate species: growth, reproduction, photosynthesis, nutritive 



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