Environmental drivers shaping mayfly assemblages in a Ramsar-declared Danube floodplain

Context Floodplains play an important role in regulating regional water and nutrient cycles in riverscapes, also supporting high biodiversity. However, ecological requirements of aquatic macroinvertebrates in such habitats are still not sufficiently studied. Aims We analysed mayfly assemblages in two habitat types (near natural and anthropogenically disturbed) in a Danube floodplain. Methods Over a 2-year period, the mayfly nymphs were sampled at a total of 14 study sites in each season by using a benthos hand-net. Key results We recorded a low (five species) mayfly species richness. Owing to the reduced influence of the Danube River, i.e. the lower water level fluctuations and the greater habitat heterogeneity, the mayfly taxonomic and functional assemblage metrics were significantly higher in anthropogenically disturbed habitats than in near natural ones. Mayfly assemblages were correlated with higher macrophyte abundance and species richness, pH and water transparency, and lower oxygen and nitrate concentrations in the water. Conclusions Our results confirmed the high value of habitat heterogeneity for the conservation of aquatic macroinvertebrates in extreme habitats such as floodplains of large lowland rivers. Implications Those results can be used in planning management activities of freshwater habitats in protected areas.