THE DISTRIBUTION OF BACTERIA IN LAKES 



49 



teria were fewer at the surface, more 

 numerous at 100 meters deptli than at 30 

 meters. These results were confirmed by 

 Minder (1920). Diiggeli (1924) noted that 

 bacteria showed a definite stratification in 



TABLE II 



Vertical and Horizontal Distribution of Peri- 



PHYTic Bacteria. Lake Mendota. 



Numbers of Bacteria Per Square jim Per Day 



ON Slides. Median Date of Immersion, 



July 20, 1936. 



sharply separated. Bacteria growing on 

 caseinate agar were numerous in the upper 

 layers, absent in the lower ones. Tiie latter 

 contained sulphate-reducing bacteria, while 

 red sulphur bacteria were abundant at the 

 border between the two layers. Klein and 

 Steiner (1929), working on lower Lake 

 Lunz, found cultivable bacteria to be some- 

 what more numerous at the surface and 

 near the bottom than at other levels. Fred, 

 Wilson, and Davenport (1924) fouud only 

 slight and variable differences in the ver- 

 tical distribution of bacteria in Lake Men- 

 dota. Graham and Young (1934) did not 

 find any very striking variations in the ver- 

 tical distribution of bacteria in Flathead 

 Lake; there was a slight tendency toward 

 greater numbers at the very surface and 

 smaller numbers near the bottom. 



Kusnetzow (1925). using plate cultures, 

 found no marked dift'erences in the vertical 



HYDROGRAPHIC MAP 



OF 



LAKE MENDOTA 



Fig. 2. 



the peculiar Lake Kitom in Switzerland, distribution in Lake Glubokoje. in Russia; 



This lake exhibits an upper portion of nor- but Kusnetzow and Karsinkin (1931), using 



mal water, and a lower portion high in salt their microscopic method of counting, ob- 



aiid HoS content. These two portions are served a remarkable increase (up to 6,000,- 



