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We studied grazing on the green alga Scenedesmus obliquus and the cyanobacterium Planktothrix agardhii (a microcystin-producing and a microcystin-free strain) by three different filter-feeders to compare the efficiency with which these grazers remove Planktothrix from the water. The filter-feeders were two mussel species (the invasive species Dreissena polymorpha and the native Anodonta anatina) and one zooplankton species (Daphnia galeata). On a weight-specific basis, D. galeata had the highest observed clearance rates and A. anatina the lowest. However, D. galeata was only able to feed on Scenedesmus and not on Planktothrix, probably as a consequence of the morphology of Planktothrix (filaments), since neither microcystin-producing nor microcystin-free strains were grazed by Daphnia. Both mussel species were able to graze on Planktothrix, irrespective of microcystin content. Dreissena showed an especially high clearance rate. On an individual basis, however, Anodonta showed the highest clearance rates, which are a consequence of its large biomass. Densities of Anodonta in the field, however, are presently too low to exert a high grazing pressure on the phytoplankton. We suggest therefore that water managers, who may be interested in using filter-feeders as a biomanipulation tool, focus on the improvement of settlement conditions for native bivalves, such as Anodonta, instead of exotic species like Dreissena

Faunistical Overview of Calanoid Copepods (Crustacea) from Continental Waters of Ukraine Faunistic overview together with updated checklist, comprising 38 species and 2 subspecies of calanoid copepods inhabiting fresh and brackish Ukrainian waters classified in three families and twelve genera is provided. The only freshwater calanoid species endemic to Ukraine is Speodiaptomus birsteini Borutzky, 1962, a stygobiont found once in an underground lake in the Skels'ka Cave (Crimean Peninsula). Two species, Hemidiaptomus (Hemidiaptomus) rylovi Charin, 1928 and S. birsteini are included as a threatened species in the Red Book of Ukraine. Dubious records and distribution patterns of some calanoid taxa are discussed. The calanoid fauna of Ukraine is compared with those of adjacent countries.