stone Container Corporation's wastewater contains 

 organic resin acids that are potentially toxic. However, 

 acute or chronic toxicity problems in the Clark Fork are 

 unlikely, because its discharge permit stipulates a minimum 

 river water to waste dilution ratio of 200:1 (if color- 

 treated wastewater is discharged, the minimum dilution is 

 100:1) . 



Chronic bioassay tests on rainbow trout and Ceriodaphnia 

 were conducted from May 31, 1985, to June 12, 1985, at the 

 Champion mill site by EPA (Nimmo et al. 1985) . A 30-day 

 flow-through bioassay on the rainbow trout (button-up stage) 

 and a seven-day daphnid life-cycle test were conducted using 

 a series of wastewater dilutions. Mortality of fish in both 

 series of dilution waters and waste was extremely low and 

 there was no evidence of reduced growth, indicating that the 

 test dilutions were not chronically toxic to trout. The 

 daphnids survived and reproduced in ambient water from nine 

 locations on the Clark Fork and no indication of toxicity was 

 found at any of the stations. 



On the whole, little is known about the sources, fate, 

 and transport of organic substances in the Clark Fork Basin, 

 as most monitoring efforts have focused on inorganic 

 pollutants. Further investigation of these potentially toxic 

 organics is probably warranted. 



EUTROPHICATION AND NUTRIENTS 



Excessive Algal Growth 



Algae and other aquatic plants are natural components of 

 most aquatic environments. Individual species have different 

 habitat requirements, but in geneifal, their abundance is con- 

 trolled by environmental factors such as available light, 

 temperature, and nutrients. Nutrient availability, especi- 

 ally nitrogen and phosphorus, often limits algae growth and 

 abundance. In the presence of nutrient enrichment, such as 

 domestic wastewater effluents, algae growth can be excessive 

 and a nuisance to other beneficial uses. Excessive algae 

 growth can also modify existing water quality by depleting 

 oxygen, modifying pH and alkalinity, imparting taste and 

 odor, and releasing toxic substances. Algae can also remove 

 toxins from the water column. 



The process of nutrient enrichment and accelerated 

 biological productivity is called eutrophication. In 

 undisturbed watersheds, eutrophication is a natural aging 

 process. Where nutrient enrichment is accelerated by human 

 activity, "cultural eutrophication" results. 



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