THE DISTRIBUTION OF BACTERIA IX LAKES 



47 



not eonstitnte an exhanstive bibliography, 

 but many of them carry bibliographies from 

 whieli further references may be derived. 

 In the following pages I propose to present 

 mainly the results of my own investigations 

 which have been cari'ied on through four 

 seasons on eleven lakes of Minnesota and 

 Wisconsin. For the most part the data are 

 derived from microscopic counts of peri- 

 l)liytic bacteria deposited upon submerged 

 slides, over 3.000 of which have been 

 counted ; but numerous plate counts of both 

 w^ater samples and bottom deposits were 

 also made. 



The work was begun at Lake Alexander 

 central Minnesota where observations 



m 



Pike. ]uke-perch, perch, sunfish, and black 

 bass are abundant. No chemical analyses 

 are available, bnt tlie watei- is obviously 

 very Juii'd and alkaline in reaction. Cluira 

 is an abundant bottom plant and lime- 

 encrusted Pofdiiwgetons are common. The 

 ma]i shown in Fig. 1 indicates the hydrog- 

 raphy of the portion of the lake wliere ob- 

 servations were made and also shows the 

 location of stations at which samples were 

 taken. 



Through the kindness of the Wisconsin 

 Geological and Natural History Survey 

 further data were collected during the sum- 

 mer of 1935 from nine lakes in northeastern 

 Wisconsin, viz., Brazelle, Boulder, Crystal, 



TABLE I 



Vertical and Horizoxtal Distribution of Periphytic Bacteria, Lake Alexander. 



Numbers of Bacteria Per Square mm Per Day Deposited upon Submerged 



Slides. Median" Date of Immersion, Aug. 7, 1934. 



were made through the summers of 1933 

 and 1934. This is a shalloAV, unstratified 

 hard-water lake of glacial origin. It re- 

 ceives drainage from several small brooks 

 which are dry most of the year, and dis- 

 charges into the Mississippi drainage. Dur- 

 ing the period of these studies there Avas 

 very little rainfall. The lake level Avas be- 

 loAv the IcA'el of the outlet, and the lake AA^as 

 temporarily a seepage lake. It has, how- 

 ever, all of the general characters of a drain- 

 age lake. It is highly productive. The shal- 

 low protected bays are choked AA'ith plant 

 life. The lake "blooms" in the summer. 



Helmet, Little John, Mary, Muskellunge, 

 Trout, and Weber lakes. The hydro- 

 graphic, physical, and chemical characteris- 

 tics of these lakes ha\'e been thoroughly 

 studied and the data are aA^ailable in numer- 

 ous publications of the Wisconsin Geolog- 

 ical and Natural History Survey (see Juday 

 and Birge 1930. 1931, 1933 ; Juday, Birge, 

 and Meloche 1935, 1938; and other papers). 

 Again through the kindness of the Wiscon- 

 sin group further observations Avere made 

 on Lake Mendota during the summer of 

 1936. The characteristics of Lake Mendota 

 are aA^ailable in numerous ]uiblications. 



