EFFECTS OF PULP MILL POLLUTION ON OYSTERS 
151 
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Experiment No. 3 (0.83 part per thousand) is similar in that the two specimens 
averaged only 9 hours per day open, a reduction from the records of the control oysters 
of about 50 per cent. 
Table 1 summarizes such data. All specimens which were given a fair test in 
any concentration, from 0.5 to 10 parts per thousand reacted very unfavorably 
either by dying or by remaining closed a large part of the time. Lower concentrations 
were not studied. Sulphite liquor, then, in these concentrations, appears to be defi- 
nitely harmful to oysters. 
These effects are clearly not due to the acid content of the liquor, for the four 
specimens treated with neutralized liquor died after periods of time entirely com- 
parable to those of specimens treated with acid liquor. 
At the beginning of this report attention was called to the fact that in Oakland 
Bay the oysters showed three pecu- 
liarities to an abnormal degree, 
namely, high mortality rate, poor 
meats, and lack of growth. Either 
directly or indirectly these con- 
ditions have been reproduced in 
the laboratory by subjecting normal 
oysters to various concentrations 
of sulphite liquor. The death of 
oysters as a result of the presence 
of the liquor in concentrations above 
0.67 part per thousand has just been 
described. 
It was also stated that concen- 
trations as low as 0.5 part per thou- 
sand caused specimens to remain 
closed more than the presumably 
normal control oysters. Any factor 
which causes oysters to remain 
closed abnormally at the same time 
deprives them of their due amount 
of food, for food-bearing water can 
not enter with the valves closed. 
The result would be that specimens subjected to liquor in such concentrations as 
above stated would be unable to take in as much food as normal oysters, and would 
consequently be expected to be relatively thin and watery. The results of Galtsoff , 
in his accompanying report, should be consulted in this connection, for he showed 
that an open oyster, in certain concentrations of liquor, does not take in water, 
and food with it, as rapidly as normal specimens. 
In the experiments in which water of a temperature around 15° C. was used, 
the control specimens within two to four weeks developed 1 to 3 millimeters of new, deli- 
cate shell growth. Oysters were brought in winter to the laboratory from the cold water 
in the dikes, where growth could not go on because of the low temperature, so there 
was no possibility of mistaking the new shell for some already existing. The control 
specimens, however, were the only ones which grew new shell. In no case was new 
shell growth observed on an experimental oyster. One reason for this is that when 
the oysters are in liquor solution, the very sensitive edge of the mantle, which secretes 
I l I I l I I 1 I L 
I 2 3456789 10 
CONCENTRATION OF LIQUOR IN PARTS PER THOUSAND 
Figure 33— Showing the data given in Figure 32 calculated to include the 
influence of the proportion of time the shells were open. The points 
represent death time in days X the percentage of time the valves were 
open. Since death occurs more quickly when the specimens remain 
open than when they stay closed, the values calculated as above show 
more clearly than Figure 32 the inverse relationship between concen- 
tration and death time, although individual variations are large 
