Seasonal and annual population dynamics of ciliates in a shallow eutrophic lake

Seasonal population dynamics and community composition of planktonic ciliates were studied for over a decade in a naturally eutrophic shallow lake, Lake Vortsjarv, which has a large open surface area (270 km 2 on average) and highly turbid water (Secchi depth 300 µm) gymnostomes. There was a positive correlation between ciliates and phyto- and bacterioplankton, implying that the ciliates were clearly bottom-up or food-controlled. This was further confi rmed by the positive correlation between ciliates and metazooplankton. As both bacteria and phytoplankton are coupled with resuspension of lake sediments, the large fl uctuations in water level infl uenced the ciliate community biomass annually.