Seasonal Changes in Ciliate Biomass and Composition of the Ciliate Community in Oligo-Mesotrophic Lake Jasne (Iława Lake District, Poland)

Lake Jasne, also known as Lake Czyste, is a well-known oligo-mesotrophic water body located in the Iława Lake District, Poland. Between May 2009 and June 2010 ciliate biomass and community composition were studied on the basis of Lugol-fixed samples taken from the surface waters and the near-bottom zone. The mean annual ciliate biomass amounted to 0.58 μgC l⁻¹ in the surface waters and 1.46 μgC l⁻¹ in the near-bottom zone, and therefore, the ciliate biomass is amongst the lowest estimates observed in oligotrophic waters. In the surface waters typical bimodal seasonal changes in biomass were recorded with two peaks observed in spring and autumn. In the near-bottom zone the peak was recorded only in spring. The ciliate community was dominated by prostomatids (mainly Urotricha spp.), both in the surface waters (77% of biomass) and in the near-bottom zone (54% of biomass).