engleski

Effects of habitat modification and invasive species on macroinvertebrate assemblages in the section of the Drava River between two reservoirs

Macroinvertebrates assemblages in Croatian section of the Drava River have been drastically changed by habitat modification for the purpose of hydropower plants (construction of reservoirs and artificial channels) as well as alien invasive species. In this study we investigated macroinvertebrate assemblages structure at the upstream distribution front of the alien invasive amphipod Dikerogammarus villosus in the Drava: differences between the derivation channel and the old river course of the Drava between the Ormož and the Čakovec reservoirs were examined. Benthos samples were collected on different types of microhabitats (macrophytes, stony substrate) with hand net (25×25 cm, mesh size 500 μm) in summer of 2018 at five locations in the derivation channel and seven locations in the old course of the Drava. Non-metric multidimensional scaling analysis revealed a complete separation of sites in the derivation channel and the old course. The average number of taxa were significantly higher in the old course (20.1) than in the derivation channel (11.6), while Oligochaeta, Ephemeroptera, Coleoptera and Trichoptera had significantly higher densities in the old course. Invasive species Dreissena polymorpha had much higher densities in the derivation channel, while D. villosus in low abundance inhabited only sites close to the downstream reservoir Čakovec. Observed differences between the old course and the derivation channel, as well as between microhabitats (macrophytes and gravel) in the derivation channel, were due to a higher level of hydrological disturbance in the derivation channel which is exposed to hydropeaking, while almost constant low flow is present in the old course.

invasive species ; macroinvertebrate assemblages ; habitat modification ; reservoirs ; Drava River

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