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.

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