204 
BULLETIN OF THE BUREAU OF FISHERIES 
and deposited on the bottom may be therefore regarded as a source of potential danger 
to the microscopical algae. When the bottom is stirred by passing boats or by a 
strong wind action, a certain amount of oil may again become released and float in 
Figuke 20.— Retardation in growth of Nitzschia culture in sea water and Miquel solution caused by various concentrations of 
brine. 
the water giving off water-soluble toxic substances. The adverse effect of brine is 
even more pronounced than that of the oil. 
DISCUSSION AND CONCLUSIONS 
By Paul S. Galtsoff 
Ecological and hydrographical observations presented in the first half of the 
report describe the conditions of the oyster bottoms affected by the oil-well pollution. 
Preliminary investigations carried out by Prytbercb in 1933 failed to reveal the exist- 
ence of a direct correlation between the intensity of mortality and the distance be- 
tween the affected oyster bottoms and oil wells. This is evident from an examination 
of the chart (fig. 1), showing the intensity of mortality on various oyster beds (black 
circles) and the location of active oil wells. A number of oysters, barnacles, and green 
algae were found growing on the piling of oil wells, and no unusual mortality was ob- 
served among other organisms. The presence of small numbers of oysters on piling 
of oil wells was also observed in 1934 by Galtsoff and Smith. Examination of oysters 
and plankton showed that apparently there was no interference with the development 
of gonads, spawning, and setting of the larvae. The diseased condition of oysters was 
evidenced, however, by the loss of muscular tonus and the failure of the adductor 
muscle to maintain closure of the shell. It is known that if such a condition continues 
for a long time it results in a stunted growth and abnormal shape of the shell. No 
unusual changes in the salinity of water and other hydrographic conditions, which 
might account for a great mortality, were disclosed by these observations. 
The oyster enemies, the borer, the boring clam, and the boring sponge, are rather 
abundant in Louisiana waters. Many dead oysters examined in 1933 showed heavy 
perforations caused by the boring clam and sponge, but on the other hand, at least 
