Durand, Loyal, Jr. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XXXI (1938)
Whitney, Lester V.
Microstratification of inland lakes, pp. 155-173 ff. PDF (5.7 MB)
155MICROSTRATIFICATION OF INLAND LAKES* LESTER V. WHITNEY From the Limnological Laboratory of the Wisconsin Geological and Natural History Survey. Notes and reports No. 68. INTRODUCTION It has been known for a long time that inland lakes of sufficient depth undergo a large scale thermal stratification in summer and winter. In summer, a temperate lake stratifies into an epilimnion, a thermocline and a hypolimnion. The epilimion consists of the upper water which is kept in active circulation by the wind and which has practically a uniform temperature throughout. Immediately below this stratum is the thermocline, which is characterized by a rapid decrease in temperature. The rate of temperature change is sometimes as much as 50 C. per meter or more. Below the thermocline is a body of relatively more stagnant water known as the hypolimnion in which the temperature declines gradually toward the bottom. These three strata usually show marked chemical and biological differences. In addition to this general thermal stratification of the water, there is also a microstratification in the thermocline and hypolimnion. This microstratification was discovered by means of the transparency meter shown in Figure 1. This apparatus shows the relative transparency of the water at different depths; readings were taken in 10 Wisconsin lakes in 1936 and this report is based on the results obtained in these studies. The transparency meter is similar to that used by Hans rettersson' in Gullman Fjord in 1933 and 1934. Pettersson also measured the variation of density with depth and obtained curves similar to those for temperature and density of inland lakes. He took readings at much greater depths than is possible on small inland lakes such as those in Wisconsin; readings are indicated on his graphs about every meter where the transpar * This investigation was supported by a grant from the Brittingham Trust Fund. 1 H. Pettersson. Jour. du Cons. 10 (1): 48. 1935. Also Rap. et Proc-Verb. d. Reunion5 101: 3-7. 1936.
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