EFFECT OF CRUDE OIL POLLUTION ON OYSTERS 
161 
to maintain closure when kept in air for over 72 hours after completion of the ex- 
periment. Records of shell movements of these oysters made for 2 days before 
exposure to oil and sludge showed no noticeable differences in comparison with those 
obtained during and at the end of the experiment. Examination of table 1 shows 
that the experimental oysters were open on an average of 10 to 13.6 hours daily as 
compared with 11.2 hours for the control specimens. This difference, however, is 
not significant if allowance is made for the individual variations in oysters in respect 
to duration of open periods. For example, in other experiments 16 control oysters 
in running sea water (temperature 22° to 30° C.) showed an average daily open 
period ranging from 7.5 to 14.2 hours. Hopkins (1931) states that oysters at 
Beaufort, N. C., averaged between 10 and 14 hours per day open in running water. 
Table 1. — Length of time oysters remained open in running sea water passed through surface layers 
of oil and sludge 
[July 3 to Sept. 4, 1933] 
Specimen 
Medium 
Total 
hours 
open 
Average 
number of 
hours per 
day open 
Percent of 
time open 
719 
11.2 
46.8 
Running sea water — Barre oil A 
783 
12.2 
51. 0 
Running sea water — Barre oilB 
664 
10.3 
43.2 
641 
10. 0 
41. 7 
Running sea water — Barre sludge 
870 
13.6 
56. 6 
During the last 2 weeks of the experiments 7 of the small adult oysters died, the 
losses occurring as follows: Control, 2; Barre oil A, 1; Barre oil B, 2; Pelto oil, 2; 
Barre sludge, 0. Similar losses have occurred in previous experiments not involving 
oil pollution and are believed to be due to the fact that these oysters were collected 
from a densely populated bed near the laboratory and consequently were not in as 
good condition as the larger oysters which were obtained from planted beds. 
SURVIVAL OF OYSTERS IN SEA WATER PASSED THROUGH OIL 
According to Gowanlocb (1934) the toxicity of Louisiana crude petroleum can be 
demonstrated by continuously exposing oysters to sea water passed through a heavy 
layer of oil. A similar series of experiments was conducted at the Beaufort laboratory 
using a large wooden tank having 4 watertight compartments in each of which were 
placed 25 small, adult “coon” oysters from a bed adjacent to the laboratory and 25 
large oysters obtained from planted beds in Newport River. The arrangement of the 
equipment in one of experimental compartments is shown diagrammatically in figure 
3. One compartment was used as a control and the o'ther 3 supplied with the same 
amount of running water at the rate of 20 liters per hour, which was passed through 1 
liter samples of the following oils: Barre grade A, Barre grade B, and Pelto composite. 
The experiment was in operation from March 26 to July 27, 1934. At the completion 
of the experiment it was found that there was little difference in the survival of the 
large adult oysters in the control and experimental jars, though the small oysters 
exposed to oil showed a slightly greater mortality than the controls. The results of 
this series of experiments are given in the following table (table 2). In reviewing the 
results, consideration must be given to the possibility that certain compounds in the 
oil may reduce the oxygen content of the inflowing water and that the oil itself may 
