The research into the plankton communities of Pomeranian Bay was conducted during 10 climatic seasons of 2001–2003 at 15 stations and biological material was collected with the use of Bongo type plankton net of Ø0.2 m with a mesh size # 80 µm. Eight species and 1 genus belonging to Cladocera group were found in the samples: Bosmina coregoni martima, Evadne nordmanni, Podon intermedius, Podon leuckarti, Podon polyphemoides, Daphnia cucullata, Daphnia longispina, Diaphanosoma brachyurum, Chydorus spp. The highest abundance was observed among maritime species of Cladocera: B.c.maritima (98.613 ind. ·m^–3) at station DIV in the summer of 2001, and E. nordmanni 42.363 ind. ·m^–3 at station SII in the spring of 2001. The biggest qualitative and quantitative diversity was characteristic of halophilous Cladocera, which in warm seasons of the year were a dominant group, and their total maximum abundance in August 2001 was as high as 132.162 ind. ·m^–3. During the entire research period halophilous species of Cladocera were dominant, except in the autumn of 2001, when the abundance of freshwater species of D. longispina amounted to 18.044 ind. ·m^–3. Water temperature in the Pomeranian Bay influenced the taxonomic structures and abundance of Cladocera. It was noted that in 2001 the dominant forms were filtering forms and predatory-filtering forms both marine and freshwater, in 2002 and 2003 predatory-filtering forms dominated.

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