Abstract
Protozoan communities were studied in the coastal zone of the southern Baltic Sea. Stable environmental conditions and typical, bimodal seasonal changes in the protozoan biomass were observed at the sampling site in Sopot (2003–2004). At the sampling site in Ustka (2007–2008), strong benthic resuspension and irregular impacts of fresh water resulted in atypical seasonal changes in the protozoan biomass with a summer peak only. The mean annual biomass had similar values at both sites: 43.2 μg C dm−3 in Sopot and 38.6 μg C dm−3 in Ustka. The protozoan community in Sopot was dominated by ciliates (48% of the biomass), whereas in Ustka — by heterotrophic nanoflagellates (53%).