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.

A detailed analysis of metric and meristic characters of the 0+ year class Russian sturgeon (Acipenser gueldenstaedtii Brandt et Ratzeburg, 1833) from a fish farm located in heated water is presented. The analysis involved 9 meristic and 35 metric characters of a total of 123 individuals from an experimental cage culture situated in the cooling water canal of the Dolna Odra power station. Variability of the co-called Soljan index [Soljan 1975] and of the ratio of snout width to length was explored and the relative position of barbels was determined. Certain meristic characters of the cultured juvenile sturgeons were higher, and other were lower, than the corresponding characters in a population inhabiting waters subjected to the natural thermal regime.

Research on the macrozoobenthos of the Roztoka Odrzańska (the River Odra mouth area) carried out in 1996–1997 was aimed at following, over an annual cycle, changes in the qualitative and quantitative characteristics of the benthos. An attempt was also made to identify ecological factors that control the occurrence and abundance of different macrobenthic taxa in the Roztoka Odrzańska. The results showed the macrobenthos of all sampling sites to be dominated by freshwater species. Sites 2 and 4 revealed the ecotone effect, i.e., a tendency towards increased species diversity and abundance at a border between biocoenoses.

The subject of this study was investigation of red blood cell alterations in diploid and triploid rainbow trout (Oncorhynchus mykiss). The triploid rainbow trout were obtained through the application of heat shock of 26.5°C for 20 min to eggs 20-min following fertilization. The diploids were not subjected to shock. The 3N and 2N fingerlings of rainbow trout were reared under the same condition (environment, feeding). Fish ploidal level was determined by erythrocyte size measurement and the number of active nucleoli in epithelial gill cells (NORs). Triploidy was induced in 80.86% in heat shocked treatment. It was found that the percentage of erythrocytes with segmented nuclei in triploid fish was 13.52% and was significantly higher (P<0.01) than that in diploid fish (1.06%). In addition amitosis of red blood cells only seen in triploids (0.57%). It seems that increase of nuclear segmentation is one of the important characteristics for triploid rainbow trout.