Section Page 



5 Ninety-six hour LC50 and threshold concentrations of HCN 



to fathead minnows and brook trout juveniles (ug/liter) . . 53 



6 Contents of bacteria in waters of varying trophic degree . 57 



6 Ratio of the number of saprophytic bacteria to their 



total number as an index of the cleanliness of water ... 60 



6 Oxygen consumption for respiration of organisms in 



water-bodes of various types (summer values) 66 



6 Mean mid-summer values of heterotrophic assimilation 



of CO2 in water bodies of various types 67 



7 Percent un-ionized ammonia in aqueous ammonia solutions . . 76 



8 Changes in boundary concentrations of 3 pollutants 

 influencing biomass in Vaphnia magna 85 



8 The influence of factors on the character of action of 



the pollutants on aquatic organisms 88 



8 Distribution of organisms according to their relative 

 sensitivity to toxic substances (toxobity) 89 



9 Summary of experimental conditions and sampling periods 

 used during continuous exposure of brook trout, fathead 

 minnows, and channel catfish to toxaphene 94 



9 Relation between backbone development and weight in fish 



exposed to toxaphene 95 



9 Statistical significance of the effects of toxaphene on 

 growth and hydroxyproline concentrations concentration 

 in fish 96 



9 Mean concentrations of vitamin C (pg/g of wet tissue) in 



liver and backbone and collagen (mg/g of dried bone) in the 

 backbone of channel catfish fed a diet low in vitamin C, 

 after 90- and 150-day exposures to different concentrations 

 of toxaphene 97 



10 Results of the toxicity of a copper-ammonium solution on 

 test culture of fAicJiocy&tlt. kzAu.qi.no i>a (laboratory strain, 

 5-day experiment) 103 



10 Primary production and destruction in phytoplankton samples 

 (blue-green + diatom) under the action of heavy metals. 

 Values indicated as percent of the control 105 



IX 



