PROGRESS IN BIOLOGICAL IN'QUIRIES. 1937 47 



Effect of pulp mill poUution on oysters. — At Yorktowri, Va., Dr. 

 Walter A. Chipman, K. O. Smith, and L. L. Garriss were engaged 

 in investigatino- the cause of the decline in oyster production in the 

 York River. Studies of the effects of pulp mill pollution on oysters 

 are an important part of this investigation. 



Confinning the results obtained in 1935 and 193G, observations 

 made during this year showed that oysters in the York River below 

 Claybank were healthy and marketable, while those above that point 

 Mere extremely poor and unfit for market. The shells of the upper 

 York River oysters are nnich thinner than those of the lower York 

 River oysters and the meats are much more watery. The oysters 

 of the Piankatank River Avhicli are studied for purposes of com- 

 parison were found to be in excellent condition. Chemical tests of 

 the glycogen content bear out the observational data. During the 

 year the fluctuations in the glycogen content of the three groups of 

 oysters were as follows : Upper ^'ork River, 1.65-1.88 percent ; 

 Lower York River, 2.65-5.2cS percent; Upper Piankatank River, 

 2.97-5.44 percent. 



Remarkable improvement was found in the condition of oysters 

 transplanted from beds in the upj^er York River to other localities. 

 The shells were strengthened by deposition of lime, the meats "fat- 

 tened." and the green color of the meats had disappeared. 



Additional samples of oysters were taken this year from various 

 parts of the York and Piankatank Rivers and from other areas 

 throughout the lower part of Chesapeake Bay for a study of the 

 distribution of Nematopsi't. a gregarine parasite known to infest 

 oyster tissues. It was found that the parasite infestation was quite 

 general and that oysters from many areas containing good market- 

 able oysters were infested, indicating that the poor condition of 

 the upper York River oysters could not be attributed solely to 

 parasite infestation. 



The hydrographical conditions of the York and Piankatank 

 Rivers M'ere observed regularly throughout the year following the 

 same general program described in Progress in Biological Inquiries 

 for 1936. Measurement of current velocities and of the tide in the 

 up])er York River was completed. Analysis of the completed data 

 indicates that there is little nontidal current (average 0.04 knot 

 downstream) and that the York River is ]:)rimarily an estuary. It 

 was found tliat the mean rauge of tide at West Point was 3.0 feet. 



Comparative chemical analyses of the three main effluents of the 

 pulp mill at West Point disclosed considerable difference in tlie 

 amount of phenols, total solids, and biochemical oxygen demand of 

 the three effluents. 



In view of the fact that it is impossible for the oyster to feed 

 during the time the shell is held closed, observations were made of 

 the hours per day that oysters remained open in various localities. 

 The oysters kept in the river were connected to recorders and their 

 activities under natural conditions observed. It was found that the 

 oysters of the upper York River were not open as many hours per 

 day as the oysters of the lower part of the river, the averages 

 being 15.28 hours ])er day for the upper York and 20.81 hours per 

 day for the lower York. 



