Table 1 . --Accumulated counts of individual zooplankters 

 by species by depth. Bare Lake, 1957 



the study period. If any change in abundance 

 occurred, it probably would involve an in- 

 crease in numbers under lake fertilization 

 conditions. Hence, it would appear that the 

 1957 zooplankton population was probably 

 grazed as intensely as the 1952 zooplankton 

 population or more so. It is therefore con- 

 cluded that the lake did produce at least three 

 times as many zooplankters in the summer of 

 1957 as in 1952. It is also speculated that 

 since (1) the 1957 zooplankton population was 

 three times as abundant as the 1952 popula- 

 tion, (2) the number of predators increased in 

 the same period, and (3) the grazing on plankton 

 at both times was probably heavy, the increase 

 in zooplankton as a result of fertilization may 

 have been delayed by heavy predation. Thus, 

 only in recent years has the zooplankton 

 reached an abundance consistent with the 

 raised levels of productivity occasioned by 



fertilizing. This hypothesis was not tested, 

 but is offered as a reasonable explanation 

 for the delay observed, based on the data 

 collected. 



Table 3 shows the 1957 Bare Lake net zoo- 

 plankton population abundance in comparison 

 with the summer abundance in five Colorado 

 lakes studied by Pennak (1944). The lakes in 

 both studies are of similar origin (glacial), 

 and all are comparatively small and have 

 several zooplankton species in common. The 

 comparison was made on the basis of the 

 number of organisms per liter. Protozoa are 

 not included in the table. 



These data indicate that Bare Lake is near 

 the median of the five lakes in abundance of 

 Entomostraca and Rotatoria. However, the 

 zooplankton at Bare Lake were collected with 



