Inhaltszusammenfassung

Invasion of non-native species in freshwater ecosystems often alters the indigenous macroinvertebrate community and food web structure by changing the resource availability. One of these species is the invasive amphipodDikerogammarus villosus, whose impact by predation, especially on coexisting amphipods, is still under debate. In this study, we aim to apply compound-specific stable isotope analysis of amino acid delta N-15, which is the state-of-the-art approach for marine systems to estimat...Invasion of non-native species in freshwater ecosystems often alters the indigenous macroinvertebrate community and food web structure by changing the resource availability. One of these species is the invasive amphipodDikerogammarus villosus, whose impact by predation, especially on coexisting amphipods, is still under debate. In this study, we aim to apply compound-specific stable isotope analysis of amino acid delta N-15, which is the state-of-the-art approach for marine systems to estimate trophic positions, (1) to calculate beta values (i.e., the differences in delta N-15 values of trophic and source amino acids in primary producer) for freshwater systems, based on field samples of freshwater primary consumers (i.e., mussels) from the River Rhine, and (2) use these beta values in a case study to calculate the trophic position of the invasiveD. villosusin comparison with coexisting indigenous and non-native amphipod species from the river Alb sampled in 2013 and river Speyerbach sampled in 2014, two tributaries of the River Rhine, Central Europe. Our results show that our freshwater beta values calculated for six combinations of trophic and source amino acids were lower by between approximately 0.85 parts per thousand and 5.67 parts per thousand than those found for marine animals in previous studies. This highlights that more attention is needed on the variability of the natural differences in beta values between ecosystems. By using the freshwater beta values, we showed that the trophic position ofD. villosusis comparable to those of coexisting amphipod species. These findings confirm thatD. villosushas a flexible and omnivorous feeding strategy like other amphipod species, and suggest that predation is not the main responsible factor for the impact ofD. villosuson other species. » weiterlesen» einklappen

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