The principal difference between the two stations was that at 

 Station l58 the temperatures, and hence chemical conditions, were 

 nearly unifonn from top to bottom on the days when samples were taken. 

 The stations differed al:;0 in that, at Station 1?8, there was a closer 

 relation between the amount of oxirgen and the abundance of phytoplankton. 

 The surface water was farthest from saturation (83 per cent) on June llj 

 when the spring crop of plankton was declining, and was supersaturated 

 in September, when the plankton was again abundant. However, on May 17, 

 when the spring crop of plankton was at its hei(j;ht, the water was only 

 89 per cent saturated. 



The seasonal changes in free carbon dioxide and pH vjere siralar at 

 the two stations. Methyl orange alkalinity was generally lower at 

 Station 158. The highest values were recorded in the summer and lowest 

 in the spring, with the fall values lower than those of summer but not 

 as low as those of spring. 



Station 8F . Sampling was not begun at this station until May 8. 

 The data obtained here on 10 dates are shown in Table 20. 



In most respects the conditions were similar to those foimd at 

 Stations l58 and 37A. The differences betvjeen surface and bottom 

 samples were more pronounced, in certain cases, than any found at Station 

 l58, but there were no cases of marked depletion of oxygen such as the 

 one observed at Station 37A on August 5, or at Station 59A on August 9« 

 There was an excess of free carbon dioxide in all samples taken prior 

 to September 5. An unusual feature of the record at this station was 

 the fact that the surface water remained at pH 8.0 in spite of changes in 

 free carbon dioxide over the range -O.Ii to +1.7 parts per million. This 

 lack of change in pH can be explained partially by changes in the 

 carbonate content, but obviously some other unknown factor was 



75 



