498 
BULLETIN OF THE BUREAU OF FISHERIES 
At 10 p. m. the oysters were removed from the chamber and put in fresh running 
sea water overnight. The next morning the water which had been used the previous 
day and which was full of the products of metabolism, was aerated until its oxygen 
tension was 4.80 cubic centimeters per liter and the pH was 8.0. The same oysters 
were put back in this water and their oxygen consumption again measured. It 
remained practically the same as it had been at the beginning of the experiment. 
(See Table 6.) 
The next day an experiment was run on the same oysters using fresh sea water of 
high oxygen content and normal pH (8.2) to see if the oysters had suffered any from 
their exposure to water full of the products of their own metabolism. No effect 
whatever was noticed. (See Table 7.) 
In another series of experiments the sea water was boiled under vacuo until the 
oxygen content had been reduced to less than 1.50 cubic centimeters per liter. The 
temperature during the process was not allowed to rise above 30° C. An experiment 
was performed using this water at pH 8.0. The results given in Table 8 indicate 
that at low oxygen content the rate of oxygen consumption gradually declined with 
the drop of oxygen tension. 
Table 8. — Effect of reduced oxygen tension on oxygen consumption 
[(Water under vacuo 48 hours at maximum temperature 30° C.) August 27, Oyster No. 75] 
Time 
pH 
O 2 tension, 
c. c. per 
liter, 0° C., 
760 mm. 
Oj consump- 
tion, c. c. per 
hour per 10 g. 
dry weight 
Time 
pH 
O 2 tension, 
c. e. per 
liter, 0° C., 
760 mm. 
O 2 consump- 
tion, c. c. per 
hour per 10 g. 
dry weight 
10.45 
8.0 
* 1.375 
3.15 
7.6 
0.396 
1. 610 
11.15 
7.9 
.915 
11. 07 
(i)— 
12 15 
7.8 
.825 
7.78 
5.30 
7.9 
3. 70 
1.15 
7.7 
.581 
4. 77 
6.00 
7.9 
3. 42 
5.74 
2.15 - 
7.7 
.499 
1.438 
i Air bubbled through chamber for 2 hours. 
The validity of the experiments in which the oxygen tension is decreased by 
the metabolism of the organism whose oxygen consumption is being measured, is 
open to criticism (Keys, 1930, Hall, 1929) on the grounds that the effect measured 
is not produced by a diminished oxygen tension alone but is due to the concurrent 
increase in carbon dioxide content and a corresponding decrease in the pH value of 
the water. In the light of the experiments of Wells (1913, 1918) and Shelford and 
Powers (1915), who demonstrated that fishes are very sensitive to very small changes 
in the pH and that their respiration is profoundly influenced by the hydrogen-ion 
concentration of the sea water (Powers, 1921, 1922), this criticism appears to be 
justified. It has been shown by the present investigation (Table 7) that the oxygen 
consumption of the oyster is not affected by the products of its own metabolism. 
The experiment fails, however, to check up the possible effect of the accumulation of 
the carbon dioxide which was driven out of the water when the latter was aerated. 
In order to distinguish completely between the effect of decreased oxygen tension and 
increase in C0 2 content, the following experiment was performed: Using the open 
chamber method, the rate of oxygen consumption under normal conditions (0 2 
tension 4. 0-4. 5 cubic centimeters per liter; pH 7. 9-8.0) was first determined. Then 
the C0 2 from a gas generator was bubbled through until the pH was reduced to 7.7. 
Again determinations were made and again the pH was lowered. This was con- 
tinued until the pH value of 6.6 was obtained. Because the pH could not be lowered 
