Seasonal dynamics of cyst formation of pelagic strombidiid ciliates in a deep prealpine lake

Population dynamics of the oligotrich ciliates Limnostrombidium v~ride and Pelagostrombidium fallax were recorded in prealpine Lake Constance, Germany, from February through November 1997. Simultaneously, their flask-shaped restlng cysts were collected in sediment traps. We describe for the first time the resting stages of L. viride. Motile stages and cysts of this species were restricted to ApriVMay, with a maximum flux rate of 2 X 104 cysts m-' d-l. Pelagostrombidium fallax, a dominant species throughout the year, encysted in March to June and September to November. Maximum flux rates of 1.8 X 105 and 2.1 X 105 cysts m-2 d-' were observed in spring and autumn, respectively.