EFFECTS OF PULP MILL POLLUTION ON OYSTERS 
139 
used in experiment No. 13 above and the sudden drop in the curves of hours per day 
open (fig. 14) is not so marked. This is not considered to be conclusive in any 
respect, and is presented to show that the reaction to relatively low concentrations 
is not immediate. 
Experiments Nos. 20 and 21 ( February 26 to March 80, 1980). — -During these 
experiments the temperature of the water was maintained, with the exception of a 
few days, at between 14° and 19° C. The stock liquor solution consisted of 1 part 
pure liquor to 9 parts sea 
water. Records were started 
on February 26 with all 
specimens in pure running 
water of pH 7.7 to 7.9. 
Experiment No. 21 ( 1.3 
parts per thousand). — The 
rate of flow of water enter- 
ing the mixing chamber 
was 90 cubic centimeters 
per minute and that of 
liquor solution (1:9) 1.2 
cubic centimeters per min- 
ute, resulting in a final 
concentration of 1.33 parts per thousand. The pH varied between 6.6 and 7.1. 
The graph (fig. 15) presents the activity of these specimens in hours per day 
that they remained open. Before liquor was started the specimens were open about 
23 hours per day. Specimen No. 1 did not show an immediate marked change in 
activity, but the effect appeared after a few days. From March 1 to March 17 this 
oyster was open an average of 17.15 hours per day. On the following two days it 
was gaping wide and showing very little movement, ending with death by the 20th, 
I 
I 
1 
Figure 16.— Graphs showing records of control specimens for experiments Nos. 20 and 21. The 
marked drops in the records were due to sudden temperature changes caused by stopping of 
heater. Compare with Figures 15 and 17, giving records of experimental oysters 
after 19 days of treatment. Specimen No. 2, on the other hand, was not dead until 
23 days of treatment, but, from March 1 to 21 averaged only 1.66 hours per day open. 
While both of the experimental specimens died, the control specimens (fig. 16) 
during the entire period of treatment averaged respectively 20.91 and 21.1 hours per 
day open. At the end of the experiment it was noted that both of these specimens 
showed new shell growth and that large masses of fecal matter, discarded silt, etc., 
were left. In the experimental specimens there was no growth and very little refuse 
matter was thrown out. 
66424—31 3 
Figure 15. — Graph showing records of specimens in experiment No. 21 (1.3 parts 
per 1,000). The marked individual difference in reaction is clear. Compare 
Figure 16, showing records of the control oysters 
