124 PLANKTON OF WISCONSIN LAKES 



CHAPTER VI 



THE PLANKTON OF LAKES WAUBESA AND 

 KEGONSA 



LAKE WAUBESA 



Net Plankton 



Material for a quantitative study of the net plankton of Lake Wau- 

 besa was obtained in 1913, in 1915, and in 1916; the number of sam- 

 ples each year was two, four, and twelve, respectively. The quantity 

 of water strained for each catch and the amount of dry plankton ob- 

 tained therefrom are given in table 2, p. 181. No samples were taken 

 during the winter season and the catches for the first two years were 

 made at irregular intervals in the summer and autumn ; they were se- 

 cured at fairly regular intervals in 1916, being taken at approximately 

 two week periods from May 24 to October 30. 



The largest quantity of net plankton per cubic meter of water was 

 found in 1915, while the catches taken in 1916 yielded the smallest 

 amount of dry material; the average for the former year was a little 

 more than three times as large as that of the latter year. The mean 

 quantity in the two samples of 1913 was a little larger than the average 

 for the entire series of samples of net plankton from this lake. 



Organic Matter. The results for organic matter are summarized in 

 table 29, p. 198. The quantity varied from a minimum of 471.1 milli- 

 grams per cubic meter of water in one sample collected in 1916 to a 

 maximum of 4,232.5 milligrams in one secured in 1915. The two catches 

 made in 1913 yielded about the same amount of material per cubic 

 meter, but there was nearly a threefold difference between the maxi- 

 mum and minimum amounts of organic matter in the 1915 samples and 

 more than a fivefold difference in those of 1916. The mean quantity of 

 organic matter in the four samples of 1915 was about three times as 

 large as the mean for 1916 and almost twice as large as that for 1913. 

 The eighteen samples yielded an average of 1,665.8 milligrams of or- 

 ganic matter per cubic meter of water. This quantity is nearly twice 

 as large as the organic matter in the net plankton of Lake Monona and 

 approximately five times as large as that of Lake Mendota. The per- 

 centage of organic matter in the net plankton of Lake Waubesa varied 

 from a minimum of 69.3 per cent to a maximum of 93.3 per cent of the 



