206 



tary water and abundance of submerged non-rooted vegetation 

 are the more potent factors in the failure of the plankton de- 

 velopment in Quiver Lake. 



In most particulars the averages of the analyses of water 

 from Thompson's Lake approach those of the river water, from 

 which it draws its main supply. There are less solids in sus- 

 pension (282,9) than in the river as a result of sedimentation, 

 and less in solution (44.6) — probably the effect of the small 

 amount of creek water, or of the utilization by the plankton 

 and vegetation of substances held in solution. The loss on ig- 

 nition (36.5), oxygen consumed (11.9), albuminoid ammonia 

 (.546), and organic nitrogen (1.05), all run higher than in the 

 river as a result of the greater amount of plankton. The de- 

 creased amounts of free ammonia (.422) and of nitrites (.048) 

 as compared with those in the river (.86 and .147) would seem 

 to indicate less decomposition here, while the small amount of 

 nitrates (.64) — the least of all the averages — suggests utiliza- 

 tion of these matters by the plankton, which here reaches a 

 greater development than in any of the other localities under 

 present consideration. 



SEASONAL CHANGES IN CHEMICAL CONDITIONS AND PLANKTON. 



The data concerning these changes are given in Tables X- 

 XIII., and they are presented graphically in Plates XLIIL- 

 L. They afford evidence for the following general conclusions: 



There is a major seasonal movement in the chemical con- 

 ditions which can be traced in the analyses for each year and 

 each locality. There are, in addition to this wide-spread and 

 recurrent cycle of changes, many abrupt and often considerable 

 fluctuations due to floods, while others are of minor importance 

 and apparently of local origin. The various nitrogenous sub- 

 stances to a considerable extent fluctuate together. The quan- 

 titative fluctuations in the plankton show no intimate and im- 

 mediate correlation with those of any substance determined in 

 the analyses. Certain relations of the plankton to the quantity 

 of nitrogenous substances are however indicated, but precise 

 quantitative correlations cannot be established. The operation 



