SATUROMETER 



&Mm 



PRESSURE 

 GAUGE 



GAS PERMEABLE MEMBRANE 

 (TUBING) 



FIG. 4 Diagram of modified Weiss saturometer. 



The well water was relatively soft with the 

 following mean chemical characteristics: hard- 

 ness, 34 mg/C alkalinity (as CaC0 3 ), 31 mg/6; 

 pH, 6.7. The pH increased to 7.2 to 7.4 after water 

 aeration. Complete analyses of test water were 

 summarized by Samuelson (1975). Flow rates into 

 the test tanks were set at 38 ?/min, and water 

 velocity varied from less than 3.0 cm/sec inside the 

 cages to up to 21 cm/sec in the open tank. 



Deaths and signs of GBD were observed and 

 recorded daily, or more often during Daphnia expo- 

 sures, and data were analyzed according to methods 

 modified from Sprague (1969). Time to death was 

 plotted on graph paper. For Daphnia each point 

 represented the average of duplicate tests at the 

 given concentration. For crayfish each point repre- 

 sented an individual crayfish. Time to 50% death 

 was determined by using straight-line graphical 

 interpolation on log-probit paper, where each death 

 in each test replicate was plotted, a line fitted 

 through the points, and 50% death determined 

 where the line crossed 50% mortality. Lethal thresh- 

 old mortality concentrations were determined by 

 plotting time to 50% and 20% death at each test con- 

 centration for Daphnia and time to 20% death for 

 crayfish. 



TABLE 1 Nominal and Measured Test Levels 

 of Total Gas Saturation 



Measured total gas saturation ("..)' 



N Mean £ SD 



Range 



'Test No. = WFTSTest No.: 

 6 = 30,2 = 32, 8 = 8,9 = 39. 

 •Analysis with Weiss saturometer. 

 'Control tanks remained near 100% at a 

 "130% animals were accidentally killed. 



5 140.6 1.4 139.0 to 142.0 



5 130.5 1.1 129.0 to 131.8 



5 119.4 0.5 118.6 to 120.0 



7 139.8 1.1 138.0 to 141.3 



10 128.6 1.4 126.6 to 130.7 



10 119.1 0.8 117.6 to 120.0 



5 150.2 0.9 148.8 to 151.2 



3 119.2 1.1 118.0 to 120.0 



3 115.4 0.6 114.8 to 115.9 



3 114.8 0.4 114.4 to 115.3 



3 108.7 0.6 108.1 to 109.3 



45 124.7 0.7 123.2 to 126.3 



5 148.8 1.1 147.3 to 150.4 



21 141.4 1.5 139.0 to 143.6 



25 130.2 1.2 128.0 to 131.8 



29 119.4 0.8 117.6 to 120.9 



3 150.4 1.2 149.1 to 151.2 



10 139.9 0.9 138.0 to 141.3 

 12 119.3 0.8 117.6 to 120.9 



11 150.9 1.1 148.8 to 152.6 



45 124.7 0.7 123.2 to 126.3 



4 135.5 0.4 135.0 to 135.9 



31,2= 34,2=38, 4 = 8, 5.= 29, 



Daphnia Test Methods 



Known-age Daphnia magna from cultures main- 

 tained at the Western Fish Toxicology Station 

 (VVFTS) were used for testing. Rearing cultures were 

 maintained at 15 + 2°C on a 12-hr photoperiod with 

 one white-light and one Grow-Lux fluorescent bulb. 

 They were held in 3.8-C glass jars and fed a com- 

 bination of Oregon Moist Pellets®, pulverized in 

 water, and a mixed algae culture. Water was 

 changed biweekly. All Daphnia were transferred 

 with a large dropper from their rearing jars into a 

 transfer beaker and then gently poured into the test 

 cages. They were fed twice daily during testing and 

 had food in their guts when placed in the super- 

 saturated water. Lack of a heart beat or movement 

 when disturbed was used as the criterion for death. 



Effects on Freshwater Invertebrates 53 



