Original paper

Ciliate vertical distribution and diel vertical migration in a eutrophic lake

Rossberg, Marcelo; Wickham, Stephen A.


The diel vertical migration (DVM) behaviour of a heterotrophic ciliate community was monitored in a eutrophic gravel pit lake located near the lower Rhine in Germany. The purpose of the study was to determine whether DVM in ciliates occurred, if this behaviour was species-specific, and to examine factors (predator avoidance, location of prey, temperature and oxygen regimes) that could drive this behaviour. Day and night samples were taken monthly from March to October 2002. Ciliates and algae were sampled every meter and zooplankton every 2 m, from 0 to 14 m. At the same time, physico-chemical parameters (temperature, O2 and chlorophyll-a) were measured. Results show that the ciliates do perform vertical migration, but this could not be tied to differences in the diel distributions of potential zooplankton predators of ciliates. Of the putative ciliate predators, only Chaoborus performed vertical migrations, making it difficult to associate ciliate migration behaviour with predator avoidance.


heterotrophic ciliate communitygravel pit lakedvm