154 



Conservation Department 



Estimation of Quantities of Dry Matter, Organic Matter and 

 Ash in the Lake Water x 



In order to make possible a more direct comparison of the plank- 

 ton quantities than can be drawn from the numerical data ob- 

 tained, samples of lake water were collected from two to four times 

 at each plankton station and from these samples the total dry 

 matter, organic matter and ash residue were estimated for the 

 water of Cayuga, Seneca and Oneida lakes (Chart 9). 



Seneca 



Oneida. 



Cayuga. 



Chart 9. Showing weights of dry matter and organic matter, estimated in 

 pounds contained in an acre of water to a depth of 10 meters (32.8 

 feet), in Cayuga, Seneca and Oneida lakes. 



Method: The water samples were taken in duplicate from five 

 depths ranging from the surface to 50 meters for each station in 

 Cayuga and Seneca lakes and from the surface to 15 meters in 

 Oneida lake. From each sample of water one liter was measured 

 in a volumetric flask. This liter sample was then reduced to about 

 5 cc. with a Foerst centrifuge number 14, on the same day that it 

 was collected or else formalin was added to preserve it until the 

 next day when it could be centrifuged. This reduced volume was 

 carefully transferred to a porcelain crucible and dried to constant 

 weight in a Freas oven at a temperature of 98° C. for 24 hours, 

 cooled in a dessicator, weighed, and then the dried residue ashed 

 in an electric muffle furnace. The crucibles were heated to a dull 



i The analytical work upon which these estimations are based was done by 

 Mr. P. R. Burkholder in the Laboratory of Plant Physiology, Cornell Uni- 

 versity. The water samples from Oneida lake were transferred to the Cornell 

 laboratory where they were dried and ashed. 



