62 



PROBLEMS OF LAKE BIOLOGY 



of the oligotrophic lakes). But both on 

 submer<ied slides and agar plates, the kinds 

 of bacteria found in the dystrophic lakes 

 are obviously quite different from those 

 found in the eutrophic-oligotrophic series. 

 On slides, filamentous iron depositing' bac- 

 teria such as Leptothrix crassa and Actino- 

 myces ferrngineus are abundant, though 

 they are entirely absent from the eutrophic 

 and oligotrophic lakes. On agar plates, 

 there are very few chromogenic bacteria, 

 while spore-forming species are dominant, 

 in cultures from the dystrophic lakes. It 

 will probably be discovered that the differ- 

 ences between dystrophic lakes and the 

 others, so far as bacteria are concerned, are 

 qualitative rather than quantitative. 



The numbers of bacteria in the bottom 

 muds serve to classify the lakes roughly, i.e., 

 they are high (on the average) in the eu- 

 trophic lakes, low in the oligotrophic ones, 

 and intermediate in the dystrophic ones. 

 The counts of bottom bacteria were made 

 contemporaneously with those of the w^ater, 

 identical plate counting methods were used, 

 and they represent about an equal number 

 of samples. The two sets of data are there- 

 fore equally accurate. There is not a very 

 good correlation between the counts for 

 water and for bottom deposits. It follows 

 that the numbers of bacteria in the bottom 

 are influenced by factors other than the 

 growth of bacteria in the overlying water. 



Henrici and McCoy (1938) made an in- 

 teresting computation of the relative num- 

 bers of bottom and water bacteria of these 

 lakes. By multiplying the average number 

 of bacteria per cubic centimeter in the mud 

 by the length of the column of the sample, 

 and similarly multiplying the average num- 

 ber of bacteria per cubic centimeter in the 

 water by the depth of the lake in centi- 

 meters, there were obtained figures which 

 roughly expressed the total numbers of bac- 

 teria in the lakes, rather than the concen- 

 tration only. From these figures, the ratios 

 of total bottom bacteria to total water bac- 

 teria were computed. The results for the 

 eutrophic lakes were as follows : Alexander, 

 5.0; Little John, 1.9; Muskellunge, 0.7; 

 mean, 2.5. For the oligotrophic lakes the 



following figures were obtained : Trout, 1.8 ; 

 Weber, 0.3; Crystal, 0.2; mean, 0.7. The 

 ratios for the two dystrophic lakes were 

 very high : Helmet, 17.1 ; Mary, 6.1 ; mean, 

 11.6. These figures, from relatively crude 

 data, suggest that possibly the ratios of 

 bottom bacteria to those in the total volume 

 of water may eventually prove to be one of 

 the characteristics of the different lake 

 types. This is suggestive of Rawson's 

 (1930) findings regarding the relations 

 between total benthic fauna and the volume 

 of lakes. 



Summary of distrihution in different 

 types of Jakes. Data are as yet too incom- 

 plete to warrant any general conclusions 

 regarding the distribution of bacteria in 

 different types of lakes. It seems safe to 

 state that bacteria are more abundant in 

 eutrophic lakes than in oligotrophic ones. 

 From the available data, it seems that eu- 

 trophic and oligotrophic lakes form a 

 graded series as regards the numbers of 

 bacteria; and that dystrophic lakes are a 

 special case, probably differing more in 

 kinds of bacteria than in numbers. Num- 

 bers of bacteria in the bottom deposits do 

 not correlate well with numbers in the 

 water ; it is suggested that the ratio of bot- 

 tom bacteria to water bacteria may eventu- 

 ally prove significant in classifying lakes. 



Eeferences Cited 



Alsterberg, G. 1927. Die Sauerstoffschiclitung 



der Seen. Botan. Notiser, Lund, 255. 

 Baier, C. 1935. Studien zur Hydrobakteriologie 



stehenden Binnengewasser. Arch. f. HydrobioJ., 



29: 183. 

 Bavendamm, W. 1924. Die farblosen uiid roten 



Schwefelbakterien. Heft, 2, Pflamenforscliung, 



Jena. 

 Behning, a. 1928. Das Leben der Wolga. Die 



Binnengewasser, 5, Stuttgart. 

 Bere, K. 1933. Numbers of Bacteria in Inland 



Lakes of Wisconsin as Shown by tlie Direct 



Microscopic Method. Int. Eev. ges. Hydrobiol. 



u. Hydrogr., 29 : 248. 

 BiRGE, E. and Juday, C. 1922. Inland Lakes of 



Wisconsin. I. The Plankton, Its Quantity and 



Chemical Composition. Wis. Geol. and Nat. Hist. 



Surv., Bull. 64, Sci. Ser. No. 13. 

 BucHNER, H. 1893. Ueber den Einfluss des 



Lichtes auf Bakterion und liber die Selbst- 



reinigung der Fliisse. Arch. f. Hydrobiol., 17: 



179. 



