THE EFFECT OF WATER-GAS TAR ON OYSTERS. 
By PHILIP H. MITCHELL. 
For a number of reasons it has become desirable to know the effects of oily and 
tar-like wastes on marine life of economic importance. Damages have been claimed 
for pollution of oyster beds by wastes from the manufacture of gas. A report to the 
Rhode Island shellfish commission has attributed to v/ater-gas tar harmful effects to 
oysters in Narragansett Bay.® Tar of various sorts is used for coating piles or stakes, 
which might be in proximity to shellfish. Oily wastes are constantly escaping from 
passing craft in inland waters. 
The present investigation does not cover the entire subject, but is confined to one 
important phase — the effect of water-gas tar on oysters. The experiments made 
during the summer of 1912 at the laboratory of the Bureau of Fisheries at Woods Hole 
could not then be carried further. 
The tar was obtained from the separator at the works of the Providence Gas Co. 
on October 25, 1910, and was a mixture of the heavier and lighter tars as obtained 
in the manufacture of water gas, using an average temperature of i ,450° F. An analysis 
of tar taken under comparable conditions from the same separator at another time 
showed, according to the records of the Providence Gas Co., the following analysis: 
Specific gravity at 65.5° F., i. 050. 
Water 
Light oil at 200° F 
Dark oil at 400° F 
Medium pitch 
Free carbon 
Per cent 
by volume. 
. . . 7. 65 
• 13- 95 
... 42. 20 
... 36.20 
... 2. 70 
Three series of experiments were made. In the first, oysters were exposed to 
water-gas tar in stagnant sea water; in the second series they were exposed to the 
tar in running sea water; while in the third small amounts of water-gas tar were intro- 
duced inside the shells of oysters. 
SERIES I. 
Experiment i . — An oyster, marked with a file for identification, as were all the 
oysters used in these experiments, and weighing 83.2 grams, was put into a battery 
jar with 40 c. c. of water-gas tar and 2,500 c. c. of sea water. On the following day 
the water was changed by the method used in all the experiments of this series. A 
siphon delivered sea water from an aquarium to a point about 2 inches from the bottom 
of the jar, while another siphon at the same time drew off water from the middle of the 
jar. Water was allowed to run thus 10 to 15 minutes. As the tar stuck to the sides 
o Field, G. W. In Annual Report of the Commissioners of Shell Fisheries, Rhode Island, 1906, appendix D, p. 46-64. 
201 
