The effect of temperature and density on the amplitude of vertical migration of Daphnia magna

Abstract
The amplitude of vertical migration of Daphnia magna from warm to cold water was inhibited in thermally stratified columns in acrylic tubes. Changes in water density alone did not affect vertical movement. Abolition of the descending blue dance could not explain the results because the light source had a spectrum shifted to the red region. The magnitude of vertical migration may be reduced by an avoidance reaction to cold temperatures commonly observed in temperate lakes during summer stratification.