Cliloride ani Nitrogen 



Determinations of chloride and nitrogen were made onl^"- in the months of 

 July, August and Septenfcer of 1930. In the Island Section samples were taker, 

 at Stations l8, 31k, $9k, l58, 72, and 8F (Fig. 1). Sarnies were taken at 

 the surface an-' near the bottom. In general the two saoiples agreed very 

 closely; so closely that it is unnecessar^'^ to present both sets of data. In 

 Table 21, only the means are recorded and in Table 22 the data are further 

 suimarized by recording the mean of the Tieans for each station, and for all 

 stations co-nbined. 



Refer-nce to Table 21 s'-iows that the earliest sample was taken on July 11 

 and the latest on Seotember 2ii. This period of time is too short to give much 

 information on seasonal changes, especially because the sampling program was 

 somewhat irregular and did not include all stations in each period of two 

 weeks. Only in the nitrate nitrogen was there a change sufficiently definite 

 and consistent to be regarded as an undoubted seasonal change. During the 

 period covered by the chemical determinations, the phytoplankton increased, 

 slowly at first and rapidly later (Fig. ih) . Along viith this increase there 

 was a fairly general decline in the aiaount of nitrate nitrogen. At every sta- 

 tion except 8F, the last determination of the season was the lowest, and at 

 Stations l8 and 72 the downward trend was unbroken. The decline in nitrate 

 was due, very probably, to rapid withdrawal by the multiplying plants of the 

 plankton. 



Among the other forms of nitrogen, the changes were so irregular and in- 

 consistent that no definite connection with the changes in abundance of phyto- 

 plankton is evident. Probably a wort- regular sampling p rogram carried on over 

 a period of several months viculd show definite seasonal trends such as were 

 ''ound by Domogalla et al. (192$ and 1926). However, perfect correlation be- 

 tween nitrogen and the plankton is not to be expected because of the complex- 

 ity of chemical and biological processes in p lake. Changes in the nitrogen 

 compounds are continually taking place as a result of the activities of ammon- 

 iafying and nitrifying bacteria, and of the chlorophyllaceous plankters. In 

 view of the inadequacy of the data at hand, further discussion of the question 

 T/ill be omitted fror. this report. 



The amount of chlorine as chJLoride ranged from 8.6 to 11.7 parts per 

 million with a mean for all stations of 10.3 (Tables 21 and 22). Station 3F 

 was the only one to show chloride below 10.0 consistently. It will be shown 

 later that Detroit River is quite consistently low in chloride, and it seems 

 probable that the northern location of Station 8F makes it subject to the 

 influence of water from the river more than are the other stations. The 

 extreme range noted above (8.6-11.7) was recorded for Station 72, the most 

 westerly of the stations. Except for the single low value, chloride was con- 

 sistently above 11.0, and th> mean for all dates was 10.9. Probably this 

 station is usually affected by water from the southwest corner of the lake, 

 where chloride is regularly high, and only occasionally by water from the 

 more distant Detroit River. Stations other than 72 had rather small varia- 

 tions in the amount of chloride. 



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