Abstrakt
We studied the vertical distribution of Daphnia ephippia in the sediment of four Bohemian Forest mountain lakes - Černé, Čertovo, Plešné and Prášilské. Daphnia cf. rosea (traditionally labelled as D. longispina) currently lives in Prášilské Lake only; Daphnia populations had become extinct in the remaining three lakes during the 20th century due to anthropogenic acidification.
The distribution of ephippia (chitinous casings of the resting eggs) in the sediment can be used as a simple marker of sediment disturbance: we are comparing the ephippia profiles in the cores with the historical records of the Daphnia presence in the lakes. Vertical profiles of ephippia densities in several cores did not agree with the historical data.
Ephippia were often present near the surface of the sediment, which confirms that the sediment must have been disturbed after the Daphnia extinction. This has been caused by the extensive human activity in the past: the previous limnological research as well as various other activities repeatedly affected the sediment record in all lakes.
Therefore, any future paleolimnological studies in these valuable natural localities should be limited to deeper sediment layers.