Original paper

Quick springtime changes in community structure of pelagic ciliated protozoa

Zingel, Priit; Paaver, Tiit


Quick changes in community composition and population dynamics of planktonic ciliates were studied in the ponds of two fish farms obtaining water from different sources (from a fast flowing river or a stillwater reservoir). Samples were taken at two-day intervals during a short period after springtime filling of the ponds. At the beginning of the investigation period the community in the lotic ponds was dominated by species that favour periphyton or benthos as their habitat. They were gradually replaced by euplanktonic species. In the lentic ponds euplanktonic species dominated throughout our study. The similarity index ISJ between lotic ponds and their inflow was 0.67 at the start of our study but decreased to 0.2 during 14 days. If the inflow was from a stillwater reservoir, the similarity index decreased only moderately. In the lotic ponds ciliate community shifted from bacterivory to algivory while in the case of lentic ponds the situation was the opposite – algivorous species were gradually replaced by bacterivores. Abiotic and biotic factors that determine ciliate community structure were separated. The abiotic features are ruling when the system goes through major changes (in our study the lotic pond system where water flow ceased dramatically). The biotic factors are crucial in more stable systems (in our study the lentic pond system) and can change the community structure in same degree as the abiotic ones.


successionsimilarity indexciliatesfeeding typeshabitat