AME 29:181-188 (2002)  -  doi:10.3354/ame029181

ABSTRACT: The seasonal dynamics of strombidiid ciliates in alpine Lake Mondsee, Austria, were studied from September 1999 to November 2000 and in April/May 2001. Simultaneously, their resting cysts were collected in sediment traps. Concentrations of active strombidiids at 0 to 20 m depth ranged from 50 cells l^-1 (February) to 2100 cells l^-1 (May). The genera Pelagostrombidium and Limnostrombidium coexisted during all seasons, with Pelagostrombidium being the dominating taxon, contributing 70 and 83% to total strombidiids in September 1999 and May 2001, respectively. Throughout the study period, only 1 cyst type was observed, which in size and shape matched a previous description of Pelagostrombidium cysts. Maxima of cyst production (up to 2 x 10⁵ cells m^-2 d^-1) occurred in October/November, while virtually no cysts were detected in winter, spring and early summer. The absence of a spring maximum of cyst formation contrasts with earlier observations from pre-alpine Lake Constance. We explain this finding by a different timing of strombidiid development, relative to the phytoplankton spring bloom in both lakes.

KEY WORDS: Pelagostrombidium · Limnostrombidium · Cyst · Lake Mondsee · Lake Constance