engleski

Biocontamination of benthic macroinvertebrate communities of four major large rivers in Croatia

Rapid spread of alien and invasive macroinvertebrates across European freshwaters during the last hundred years has caused dramatic changes in structure and function of macroinvertebrate communities, especially in large rivers. Biocontamination of macroinvertebrate communities of Croatian large rivers has been sparsely studied. The aims of this study were to assess the most recent (2015) biocontamination level of macroinvertebrate communities along all four major large rivers in Croatia (Danube, Sava, Drava and Mura) and to establish temporal changes of biocontamination by comparison of our results with previous study. Twenty quantitative samples of 0.0625 m2 in a shallow bank area were collected once in 2015 at 46 sites along the Croatian sections of Danube, Sava, Drava and Mura Rivers using hand nets (mesh size 500 μm). Danube has the highest number of invasive species while Sava and Drava have subset of Danube alien species. The whole Mura River and the most upstream reaches of Drava and Sava in Croatia have not yet been heavily colonized by invasive invertebrates. Sava has been heavily invaded up to ~640 km from the mouth and the main course of Drava up to the last reservoir Donja Dubrava (~250 km from the mouth). The most dominant and widespread invasive species are amphipods Dikerogammarus villosus, D. haemobaphes and two Chelicorophium species, and clams Dreissena polymorpha and Corbicula fluminea. Middle parts of both Sava and Drava have the highest biocontamination level mainly due to high abundance of Chelicorophium spp. and invasive gammarids. Biocontamination levels are mostly stable in Danube and long-time colonized lower and middle parts of Sava and Drava. However, increasing biocontamination levels have been observed in the upstream reaches of Sava and Drava, mostly at the fronts of upstream spreading of invasive gammarids (D. villosus in Drava and D. haemobaphes in Sava). Continuous monitoring of the most invasive species spread and assessment of their impact on macroinvertebrate communities are essential prerequisite for better understanding of the changing ecological state of large rivers.

biocontamination ; benthic macroinvertebrates ; large rivers ; Croatia

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