Table 11. 



-Average nitrogen content in eastern Lake Erie, summer of 1928 



Date 



July 29-Aug. 1 

 Aug. 28 -Sept. 3 



Sept. 12-14 



Mean depth 

 of samples 

 (meters) 



10 



0.5 

 20 



0.5 

 17 



Albuminoid 



ammonia 



(p. p.m. of N) 



0.070 



0.089 

 0.086 



0.090 

 0.093 



processes of lake organisms may appreciably reduce 

 the amount of ammonia and nitrates in solution has 

 been shown by Domogalla, Juday. and Peterson (1925). 

 Examination of the nitrogen content of eastern Lake 

 Erie in the summer of 1928 shows moderate amounts 

 of albuminoid ammonia, free ammonia, and nitrates. 

 The results of the analyses are recorded as parts per 

 million of nitrogen in table 11. 



There was a fairly uniform distribution of albu- 

 minoid nitrogen with perhaps a slight preponderance 

 in the Buffalo region (fig. 22). The lowest figure re- 

 corded is 0. 06 p. p. m. at a depth of 20 meters in 

 July and the highest is 0. 117 p. p. m. at the surface 

 of station 03 in August. Throughout the summer 

 there was a gradual increase from an average of 0. 070 

 p. p. m. in July to 0. 088 in August and 0. 092 in Sep- 

 tember. These data indicate an increase in organic 

 matter with advance of the season. 



The free ammonia content was somewhat lower 

 than recorded for other lakes by Domogalla, Juday, 

 and Peterson (1925). The range in Lake Erie was 

 from 0. 005 to 0. 038 p. p. m. The means of the ob- 

 servations suggest a marked increase at the surface 

 in September. The ammonia content at intermediate 

 depths in July averaged 0. 014 p. p. m. In August, at 

 the surface, it averaged 0. 015 p.p. m. and in Sep- 

 tember there was in increase to 0. 030 p. p. m. In 

 August there was about the same concentration of 

 ammonia at both the surface and bottom, but in Sep- 

 tember there was more than twice as much at the 

 surface. 



The region along the southern shore from Dun- 

 kirk to Buffalo appears richer than the other areas 

 examined (fig. 23). Increases are conspicuous in 



Free 



ammonia 



(p. p. m. of N) 



0.014 



0.015 

 0.014 



0.030 

 0,013 



Nitrate 

 (p.p. m. of N) 



0.150 



late summer, especially at the surface. The rela- 

 tively low concentration of ammonia at the bottom 

 is peculiarly different from what might have been ex- 

 pected in the light of analyses on the Wisconsin lakes. 



I 

 Nitrates were relatively more abundant than the 

 free ammonia and albuminoid nitrogen. The results 

 of the nitrate analyses (fig. 24) indicate a fairly uni- j 

 form horizontal distribution. There was some re - 

 duction, however, in the surface nitrate, which may 

 be due to its utUization by plankton. 



I 



The greatest concentrations occurred at inter 

 mediate depths in July when 0. 20 p.p. m. was record- 

 ed at a number of stations. The minimum quantity 

 of 0. 08 p. p. m. was found at the surface of station 15 

 in August. The average for all stations in July was 

 0. 15 p. p. m. , in August 0. 123 p. p. m. , and in Sep- 

 tember 0.137 p. p.m. 



The free ammonia content was greater at the sur- 

 face than at the bottom and increased toward autumn. 

 Nitrates were more abundant at the bottom than at the 

 surface and also showed autumnal increase. The albu 

 minoid ammonia was about the same at the surface 

 and bottom, and changed little during the summer. 



Dissolved Oxygen 



The dissolved oxygen content throughout the sum 

 mer months was relatively high. Analyses of the sur- 

 face samples indicate a high percentage saturation at 

 all stations in open lake waters. The mean percentag 

 saturation at the surface in the summer of 1929 was 

 94. 9. The bottom mean for the summer was 83. 3 per 

 cent. These figures are higher than tJiose obtained in 

 the eastern area during the preceding summer when tl 



72 



