suoersaturated; but on May 21, when the plankton was at its heif'ht, th« 

 vater was onlj'' 89 per cent saturated. There was no evidence of marked 

 withdravjal of oxygen follovdnt^ the decline of the plc.nkton, as there vjas 

 in 19^9' Apparently other factors, such as temperature and sunlight, 

 tended to mask the relationship on'the dates that samples were taken. On 

 several dates there were marked differences between top and bottom samples 

 as a result of temporary sta^^nation of the lover water. The smallest 

 amount at the bottom was U.9 parts per irdllion on August 5. Presumably 

 "ihio rcnresented a very low per cent of ;satui-u.tion, but temperatures are 

 not available tc determ3.ne this point. On Auf^ust 9 the temperature cit 

 the bottom was 18,2°, which was almost 3 degrees lower than on July I8. 

 If we assume that the bottom temperat.ure on August S was also 18,2", the 

 water would have been only b? per cent saturated. 



The pH at the 3ui'face rant;ed frcn. 7.8 to 8.3. In ^reneral, changes 

 in pK were in agreement with changes in free carbon dioxide. At the 

 bottom, oH ranged from 7.6 to 8.3 • The lowest value accompanied the 

 largest amount of free carbon dioxide. The most marked difference betvreen 

 surface and bottom (0.5 unit) vjas observed on August 5. On September 6 

 the pH was higher at the bottom than at the surface. 



Methyl orange alkalinity ranged from 89 to 103 parts per million. 

 V.lth few exceptions the amounts at the surface and bottom were nearly 

 the same. In general the spring samples showed a smaller amount than 

 the summer samples and there was a decrease in early fell, but the surface 

 sample of October 2 was unusually high. 



A compari!!on of the data for 1929 and 1930 brings out some notable 

 •iifforencer. Air tomneratures during the pej'iod May-September, 1930 were 

 considerably higher than for the corresponding period in 1929 (Table h) . 

 Since the surface water warmed more rapidly, there was greater resistance 

 to nixing and the lower water 'iras kept from contact '.dth the air for longer 

 periods. As a result, the differences in chemical conditions between surface 

 and bottom were more pronounced. Another difference between the two years 

 was the greater length of time in 193C during v/hich there was an excess of 

 free carbon dioxide. A deficiency of the gas at the surface waS observed 

 only once prior to August, whereas in 1929 there was an excess on only one 

 occasion. A third difference -was in the absence of a definite relationship 

 between the chemical conditions and the abundance of plankton, particularly 

 in the spring. 



Station 1$8 . Samples ;.'ere taken here on 12 dates between early April and 

 early October. The data are shown in Table 19 . Conditions at this station 

 and Station 37A v/ere so similar that there is no necessity for a detailed 

 account. 



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