Planktonic ciliates in Western Basin of Lake Ringsjön, Sweden: community structure, seasonal dynamics and long-term changes

summary Temporal changes in species composition, abundance and biomass of planktonic ciliates in Western Basin of Lake Ringsjon, Sweden, were studied in 1988-1990 and 1998-2000. In total, 49 species were found. The most common species were Tintinnidium spp., Halteria grandinella, Strombidium spp., Strobilidium spp., Coleps hirtus and Vorticella spp. The planktonic ciliates ranged in abundance from 1.2 and 1.6 to 82.0 and 41.0 cells l -1 ×10 3 during the investigation, with a mean of 16.38 and 9.74 cells l -1 ×10 3 , respectively. Biomass of the ciliate communities ranged from 27.6 and 50.0 to 1939.3 and 2182 µg l -1 . In terms of abundance and biomass, small Oligotrichida species were very important for the lake. The seasonal dynamics of the ciliates in Lake Ringsjon had a pattern typical of eutrophic lakes. Species composition in 1988-1990 and in 1998-2000 was very similar. The annual mean abundance and biomass of ciliates decreased at a large scale. The patterns of temporal distribution of some dominant species showed some changes.