i 



however, receives industrial wastes, and hence is open to more than one 

 interpretation, although there is no doubt in my am mind that oil is 

 the chief cause of the destruction evident." 



EXPERIMENTS WITH OYSTERS, OSTREA VIRGINICA GM 



Because of its great economic importance, the oyster has been studied 

 both in this country and abroad more than any other marine invertebrate. 

 Consequently, its physiology, habits, and life histroy are better known 

 than those of clams and other lamellibranchs. The oyster is one of the 

 most common organisms of inshore waters where it lives attached to rocks 

 or lying on the bottom from levels of about halfway between high and low 

 water marks to depths of about 40 feet or more. In this situation it is 

 frequently affected by oil wastes discharged into -waters. Having no means 

 of moving from unfavorable environments, the oyster protects itself by 

 tightly closing its valves. If the inimical condition persists, the oyster 

 is eventually damaged or killed. Methods for studying the response of the 

 oyster to altered water conditions have been worked out by previous investi- 

 gations conducted by the Service and have been applied several times in 

 pollution studies (Galtsoff, 1928; Hopkins et al,, 1931; Galtsoff et al., 

 1947; Chipman, 1948). They consist in recording the time of opening and 

 closing of the valves of the oyster, observing the character of the muscular 

 movement, and the rate of pumping of waters by the gills. The methods of 

 obsei^ng and testing the reactions of oysters to the presence of oil in 

 water employed by us in the present work are given separately with the accounts 

 of the different experiments. 



!• Toxicity of oil and of oil and carbonized sand mixtures in 

 standing solutions t 



the purpose of these tests was to find out whether oysters oein survive 

 high concentrations of oil in standing water, and whether the toxic effect 

 is reduced by treatment of the oil with carbonized sand. The conditions 

 of the experiment must be regarded as comparable to the most adverse case 

 of oil pollution that the oyster may suffer. 



The tests were conducted in the College Park laboratory using adult 

 Chesapeake Bay oysters which were carefully washed and scrubbed with a 

 fiber brush to remove the attached fouling organisms. Three groups, each 

 comprising twelve oysters, were placed in glass aquaria containing 10 

 gallons of sea water collected at the same place and time that the oysters 

 were taken. The salinity of water in the Bay was 13 parts per thousand. 

 It was maintained at this level in the aquaria by additions of distilled 

 water to compensate for evaporation. The water was aerated. A continuous 

 record of temperature was obtained by means of a recording thermometer, the 

 bulb of which was immersed in a glass cylinder filled with distilled water 

 and set in the control aquarium. TVro sets of tests were made using 200 ml* 



29 



