PROGRESS IN BIOLOGICAL INQUIRIES. 21 



Consequently, in approaching the vital problems of the oyster in- 

 dustry of this region it is impossible to escape attack upon the ques- 

 tion of pollutions. Here both chemical and biological problems are 

 involved. The analytical chemist ascertains wnat substances of 

 possible toxic nature are discharged into the waters; the biologist 

 must determine by experiment the effects of such substances upon 

 the existence and growth of oysters and their efficiency in breeding, 

 and must find the precise degree of concentration which is injurious; 

 finally, the engineering chemist must discover how such substances 

 may be either eliminated altogether from effluents or at least kept 

 within the bounds of safety as indicated by the biologist. 



Such investigations by analysis and experiment are now being 



grosecuted by the Bureau of Fisheries in cooperation with the 

 lureau of Chemistry, and probably something of a more definite and 

 satisfactory nature may be embraced in a subsequent report. 



EFFECTS OF LOWERED OXYGEN SUPPLY UPON OYSTERS. 



While the investigation of the subject of pollution as affecting 

 oysters is one of some complexity, it is known that one of the most 

 immediate effects of pollution, generally speaking, is the reduction 

 of the oxygen content in water. During the summer of 1919 an 

 investigation was conducted by Dr. P. H. Mitchell, director of the 

 Fisheries Biological Station at Woods Hole, Mass., to determine the 

 effects of lowered oxygen content on the survival of oysters, the work 

 being done in both field and laboratory. 



Observations in the field were based upon a series of small plants 

 of oysters in Seekonk River, a tidal estuary at Providence, R. I., 

 and in Providence River, below the mouth of Seekonk River. De- 

 terminations of the dissolved oxygen in the water at the locations 

 selected were made at various times and under various tidal and 

 weather conditions. The results indicated a substantial mortality of 

 oysters where the average dissolved oxygen content was 26 per cent 

 of saturation or less and nearly all oysters died within a period of 

 50 days where the percentage of saturation was less than 12. 



Observations in the laboratory were conducted by keeping oysters 

 in small containers furnished with sea water of varying oxygen 

 content and subject to as definite control as possible. The results 

 indicated that the minimum oxygen content of water that will sus- 

 tain oysters during a period of one month is between 25 and 33 

 per cent of saturation. Further experiments are planned to deter- 

 mine the effect of lowered oxygen supply upon the propagation of 

 the surviving oysters. 



Another series of experiments has substantiated the earlier find- 

 ings of copper storage as the explanation of the appearance of a 

 bluish-green color, and recent results point to a possible significant 

 relation between the development of the undesirable blue-green spots 

 and the deprivation of oxygen. 



OYSTER INVESTIGATIONS IN GREAT SOUTH BAY. 



Dr. Churchill and Mr. Gutsell completed a report upon the spawn- 

 ing of oysters and setting of oyster larva? in Great South Bay, Long 

 Ishiiid. The conditions in this shallow bay offer a contrast to those 



