EFFECT OF OIL POLLUTION ON MARINE AND WILD LIFE 179 



Avere so slippery. Since this plant, has been rendering garbage, the only sets of 

 oysters have been in the upper MuUica River some 10 miles from the plant 

 The former great natural oyster bed at the Gravelling, at the mouth of the 

 river, has not received any set of consequence during this same period, 

 though formerly it was one of the most productive in the State. 



We have been studying the Great Bay region since 1900, and during this 

 time there has been no apparent change in conditions there other than the 

 change from fish rendering to garbage salvage, as indicated. It is perhaps 

 significant that great numbers of mussel larvae are found in late April or early 

 May, when the weather is as yet not warm enough to cause much loss of 

 grease from the garbage scows. 



3. Regarding the effects of oil upon adult oysters let me cite experiments 

 which I performed in 1920 in preparation for testimony in the case against an 

 oil company at Providence, R. I., in May, 1921. The oysters were kept in 

 two tanks of bay water of known purity ; one tank served as control, the other 

 was kept covered by a film of oil. The water in both tanks was frequently 

 agitated to simulate wave action, and at no time did the oxygen saturation fall 

 below SO i>er cent. (It has been shown that oysters do not suffer until the 

 saturation falls below about 30 per cent.) After 15 days the oysters from the 

 two tanks were opened and compared. Those from the oil-covered tank showed 

 marked contraction of the mantle, the blood vessels revealed many bluish 

 nodules characteristic of oysters living under unfavorable conditions, and the 

 bodies of the oysters were distinctly thinner and poorer than those of the 

 controls. Preserved samples of each lot show the difference clearly even now. 



Mitchell ' failed to find effect of water-gas tar upon oysters. These experi- 

 ments are open to the objection that clear running water was used and that 

 practically all of the tar was soon deposited on the sides of the aquarium. 

 If turbid water such as that found on most oyster beds had been used, and 

 if this had been kept in agitation as is the case in wave action, then he would, 

 I atoi sure, have obtained a different result. 



^. Damage to adult oysters from oil is of two kinds — (a) a direct result of 



Sgestion of oil along with the minute particles of detritus which form so 

 rge a part of the oyster's food, and (b) an indirect result of oil upon the 

 plant and animal organisms that live upon the oyster's shell and which are 

 most important sources of nutriment. Eventually, as more and more oil is 

 carried down to the bottom, the shells of the oysters and the surrounding 

 bottom become so thoroughly impregnated with the oil that the organisms 

 used as food by the oyster can not live and multiply. 



5. The vast oyster industry of Maurice River Cove, Delaware Ba.v. which 

 did a $7,000,000 business last year, is threatened by oil and by oil alone. This 

 region is so far removed from industrial centers as to be practically free from 

 trade wastes, but oil pumped overboard by tankers unloading water balla.st 

 and from oil-burning steamships floats in large fields across these valuable beds, 

 and its presence is already demonstrable on the bottom. If the condition con- 

 tinues, the industry in Delaware Bay is bound to follow that in New England 

 and elsewhere. 



6. A most striking example of the effects of oil may be seen at low tide on 

 the .shores of Staten Island. On a warm day, with consequent increased oxida- 

 tion, soft clams (Mya) may be seen coming up to the surface of the flats by 

 the thousands, dying soon after reaching the top. The surface of the flats 

 is covered by a heavy film of oil, while the bodies of the animals reek with it. 

 This region, however, receives industrial wastes, and hence is open to more 

 than one intei-pretation, although there is no doubt in my own mind that oil 

 is the chief cau.se of the destruction evident. 



At Baltimore the writers were given the impression that harbor 

 conditions were formerly so bad that the fishing industry was very 

 badl}^ handicapped. Now, however, the trouble is not so serious. 

 Even at the present time it is necessary to go a considerable distance 

 down the bay before it is possible to catch fi.sh and other sea food 

 in large quantities. 



' Mitchell, p. H. : The Eflfect of Water-Gas Tar on Oysters. Rull., U. S. Bur. of Fish., 

 Vol. XXXII, 1912 (1914), pp. 199-206. B. F. Doc. No. 780. Wa.shlngton. 



