METAL EDGE. INC. 2004 PH7.5109.5 PAF

FROM BULLETIN OF THE UNITED STATES BUREAU OF FISHERIES : VOLUME XXXII, 1912
Document 786 : : : : : : : : : : : : : Issued February 18, 1914.

THE EFFECT OF WATER-GAS TAR ON OYSTERS
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By Philip H. Mitchell

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THE EFFECT OF WATER-GAS TAR ON OYSTERS.

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By PHILIP H. MITCHELL.

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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 water-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 1,450° 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:

Per cent
Specific gravity at 65.5° F., 1. 050. by volume.
\ UES Ge einer a ease Otte Stim ottad cra aR Aes AID Oe ta ODOT OA AGO CRO ELI
Lest orh Eker Forel SA Aen onso ciate Hone Role Sanaenede nots Qsoaoar ak hC Gy
Wark oileat acorn ian toes yen we Oe ela eee CaP Ane haar cess. eam Basso
WSR TU POMC, Jog nooo o DUOMO DeBn Losers 0 mAG Som oe Os eaten OsaDeOAoD {ese
BVEENCAT DON»... <reeeiee sin Heme ciscte seal myn cle cheba acts SARE eIae oe Way RENEE ey O.

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 1.—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 4o 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

@ Field, G. W. In Annual Report of the Commissioners of Shell Fisheries, Rhode Island, 1906, appendix D, p. 46-64.

201

202 BULLETIN OF THE BUREAU OF FISHERIES.

and bottom of the jar, or, in the case of the lighter more oily portions, floated on the
surface of the water, none, or very little of it, was removed while the water flowed through
the siphons. The water, therefore, was almost completely changed without removing
the tar. Shortly after the water had been changed the oyster was seen to be slightly
open, but could close at the slightest jar. The water was changed in this manner once
or twice daily for 10 days, The oyster was often seen partly open during this time,
but would always respond to a mechanical stimulus by closing. After 10 days the
water was no longer changed, but was left entirely stagnant. At the end of two weeks
under these conditions the oyster seemed to be affected. It now remained continuously
open, and appeared unable to close when stimulated. A few days later it showed signs
of putrefactive disintegration.

Experiment 2.—An oyster weighing 63.7 grams was treated exactly as in experi-
ment 1. ‘The results were quite the same, except that when the water was left entirely
stagnant disintegration set in after five days.

Experiment 3.—An oyster weighing 71.6 grams was treated as in the preceding
experiments, except that the tar was smeared all over the inside of the jar and on the
oysters. After 24 hours the oyster was found wide open and unable to close when
stimulated. It was removed from the jar, and was seen to have its mantle greatly
retracted. It would spring open when closed by hand. It was washed and put into an
aquarium in running sea water. Two days later it appeared to be entirely recovered,
as it would close normally when stimulated. It was then put back into the jar of sea
water and tar in which it had been at first. It was now kept in this jar during six days,
with the water changed once or twice daily. At the end of this time it had again lost
the ability to close normally, but when put in the aquarium once more it again appar-
ently recovered. About three weeks later, however, it became disintegrated.

Experiment 4.—An oyster weighing 95 grams was arranged exactly as in experi-
ment 3. The results were quite the same, that is, after 24 hours it refused to close,
but recovered when put in the aquarium of running sea water. Some weeks later,
however, it died. That its death was due to the tar is not certain, because at that time
other oysters in the same aquarium died without any previous exposure to tar.

Experiment 5.—An oyster weighing 78.7 grams was treated exactly as in the preced-
ing experiment. It, too, became unable to close after 24 hours, and when put in run-
ning sea water entirely recovered. At the end of the summer, nine weeks later, it
seemed entirely normal and had a normal appearance when opened.

Experiment 6.—An oyster weighing 62 grams was treated exactly as in the preced-
ing experiment. The result was slightly different in that the oyster did not begin to
show a tendency to remain open until after three days, and became entirely unable to
close after five days in the tarry water with daily changing of the water. It was then
put in running sea water and began to disintegrate a few days later.

Experiment 7.—An oyster weighing 70.8 grams was put into a battery jar with 20
c. c. of the tar not in contact with it and 2,500 c. c. af sea water. The water was changed
daily during the next ro days. It was then left stagnant during 8 weeks. The oyster
was sometimes observed to be open, but would then close if jarred. At the end of that

EFFECT OF WATER-GAS TAR ON OYSTERS. 203

time it was cleaned and dried and found to weigh 71.6 grams. It had formed new shell
all around the edge. Opened it gave no smell of tar, the heart was beating and the
mantle was normally sensitive to mechanical stimuli. Part of the heart and portions
oi the gills were discolored.

Control experiment.—An oyster weighing 72.4 grams was put in a battery jar with
2,500 c. c. of sea water. The water was changed during the next ro days as in the pre-
ceding experiment and was then left stagnant during 8 weeks. Examination then
showed no noticeable new shell, but the heart, gills, and mantle were quite normal.

The experiments of this series indicate that when considerable quantities of
water-gas tar are in intimate contact with oysters in stagnant water serious or fatal
effects are produced. Under these circumstances the oyster can not use its natural
defense against a relatively or entirely insoluble substance. When the water is stag-
nant, there is little opportunity to eject such substances and free the organism from
them. As will be shown later, the oyster can rid itself of water-gas tar when in running
sea water. When the tar can not be ejected it seems to produce an effect similar to
paralysis, so that the initial symptom is a failure of the adductor muscle to respond
to stimulation of the sensory nerves. No conclusions as to the structures specifically
affected can be drawn from these experiments. Whether the fatal effects produced in
five of the above experiments were due to a direct toxic effect of water-gas tar, or to
some indirect effect also, does not appear from these experiments.

SERIES Il.

Method.—Two oysters were put in each of four battery jars. Each jar was arranged
with two siphons, one bringing sea water from an aquarium to the jar with the lower
end of the siphon about 2 inches below the level of water maintained by the other siphon,
which carried water from the jar to a sink. The running water therefore tended to
carry off the light floating oils but left the heavier tar sticking to the bottom and sides
of the jar. The siphons were so arranged that each jar contained constantly about
2,500 c. c. of sea water. Into each jar there were put 30 c. c. of water-gas tar mixed
with sand and thoroughly smeared over the bottom and sides of the jar and on the
shells of the two oysters. From time to time during the following weeks small amounts
of tar were added to replace that carried away by the siphons. After remaining in
the jars as described during nine weeks the oysters were cleaned, weighed, and examined.
Comparison of their weights at the beginning and at the end of the experiments is given
in tabular form:

| |
ie | Initial | Final |
ae | weight. | weight. |
| Grams. | Grams
, if 98.0 99.0
i\ 47-8 47-8
A { 92.9 92-0
52.4 52-3
{ 96. 8 94:9 |
3 61.8 62.5
A f IOI. 1 100. 7
\ 45-2 44-3

204 BULLETIN OF THE BUREAU OF FISHERIES.

That these variations in weight have no special significance is indicated by com-
parison with the variations in the weights of oysters kept in the aquariutn during the
summer but not exposed to tar. \

| Initial Weight after
| weight. five weeks.
|

Grams. Grams.
66.5 |. 66.0
| 76.0 76.5
| 244.0 243.0

147-0 151.0

When opened all were found to be normal in appearance and function. No odor
of tar was detectable in the shell contents of the oysters, although an abundance of tar
was left in the jars at the end of the experiment. Smears of tar were also still present
on the outside of the oyster shells.

These experiments indicate that even intimate contact with water-gas tar does not
injure oysters in the course of nine weeks, provided facilities for defense in the form of
moving water frequently renewed are available.

SERIES III.

Experiment 1.—A small oyster was first pried open and injected with 0.5 c.c. of water-
gas tar. It was then put in a jar of running sea water. It remained tightly closed
during the next two hours. On the next day it was found to be quite normal. It was
open and apparently feeding, but closed when stimulated. Drops of tar near it indicated
that the foreign material had been ejected. One week later it still appeared entirely
normal. It was then again injected with 0.5 c. c. of tar, and was now put in stagnant
sea water. Four days later it did not, when stimulated, close as readily and tightly as a
normal oyster. It was then opened and found normal in its heartbeat and in con-
tractility of the bivalve muscle, but the mantle was not normally responsive to mechanical
stimulus.

This experiment indicates that when an oyster ingests tar and can not get rid of it
because the surrounding water is stagnant, some impairment of the sensory apparatus
in the mantle results. This interferes with certain activities of the oyster, prevents
normal closure, and eventually causes degeneration of muscular and other tissues.

Experiment 2.—Three medium-sized oysters were each injected with about 1.5 c. c.
of water-gas tar and then put in separate jars of running sea water. Some time after
they were seen in each case to open slightly and in a few minutes close violently so as to
eject masses of tar. This process was repeated a number of times in the course of one
to three hours after injection. They then remained constantly closed for some time, but
were found normally open on the following day. They were left in the running sea
water for a period of eight weeks and behaved throughout that time like control oysters
inthe aquarium. As it was then necessary to terminate the experiments, the oysters were

EFFECT OF WATER-GAS TAR ON OYSTERS. 205

opened and carefully examined. They were found to be normal in color, odor, heartbeat,
responsiveness of the mantle, ciliary movement, and in short in every respect.

This experiment distinctly indicates that water-gas tar in considerable doses is
harmless to an oyster in running sea water. The conditions of this experiment more
closely resemble those of the native habitat of the oyster than do those of the preceding
experiment, because tides and other currents over oyster beds maintain a constant
movement and a continuous changing of the surrounding medium.

Experiment 3.—A medium-sized oyster was injected with 1 c. c. of water-gas tar,
which was distributed all around the mantle. It was then put into about 1,500 c. c.
of sea water and carefully observed. During the next five hours it did not visibly open
and no tar escaped from it. On the following day, however, a few drops of tar were
floating on the surface of the water. During the next two days the oyster was only
infrequently observed and was not seen open, but on the third day it was found nor-
mally opened and able to close when stimulated. It was left in the same sea water
during the next two weeks. It had then developed the usual symptoms of imperfect
closure and when opened did uot show a normally beating heart or a responsive mantle.
This experiment confirms the first one of this series.

EFFECT OF WATER-GAS TAR ON THE DISSOLVED OXYGEN OF SEA WATER.

It seemed possible that tar and similar substances might in a measure reduce the
oxygen content of water so as to affect shellfish. Mixtures of tar and sea water were,
therefore, allowed to stand for varying periods of time and then tested by Winkler’s
titration method to measure the quantity of dissolved oxygen in the water. The
experiments are summarized in the following table. Three liters of sea water were used
in each case.

Time mixture | Oxygen re-

pearyonety was allowed to} maining in
pactticed! stand at room | water at end

* | temperature, of the time.

Cubte Paris per
centimeters. Hours. million.

200 20 6. 64

200 24 6. 10

200 45 -00

200 130 - 08

50 40 2.71

50 45 3.10

50 130 -08

None. 4° @7.10
None 4s @ 8.09
None. 130 28.26

@ Control, sea water alone.

These experiments show that the tar can cause the disappearance of dissolved
oxygen in sea water. How potent a factor this may be in causing the effects of the
tar on oysters in stagnant water it is not, however, safe to say. Oysters, as the author
has shown, are remarkably resistant to lack of oxygen and do not when deprived of it

VU Vel TW UII vv

206 BULLETIN OF THE BUREAU OF FISHERIES.

show inability to close except in the advanced stages of oxygen starvation. That oxygen
consumption by tar may help to account for the fact that oysters are injured by stag-
nant tarry water, while they are uninjured by the tar in running sea water, is quite
probable. In the natural habitat of the oyster, however, it seems quite impossible
that the slight reduction of dissolved oxygen which small amounts of tar could effect
would alter the results of oyster culture.

CONCLUSION.

These experiments show no noticeable effects of water-gas tar on oysters in con-
stantly renewed sea water. This is true in spite of the fact that large amounts of tar
mixed with stagnant sea water, or small amounts injected into oysters which are kept
in stagnant water, do cause serious or fatal effects. Considerable quantities (1.5 c. c.)
may be put inside the shell of an oyster kept under conditions resembling those of its
natural habitat without causing any effect. The harmlessness of the tar under these
circumstances is due apparently to the ability of the oyster to rid itself of such foreign
matter. In stagnant water the organism can not be effectively washed out, and effects
involving a loss of sensitiveness in the mantle result. That consumption of the dis-
solved oxygen in the stagnant water by tar may have some effect on oysters is a
possibility.

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