Changes in the Baltic Sea coastal food web: A case study on the invasion of Round goby Neogobius melanostomus (Pallas, 1814)

We used dynamic food web modeling to assess the trophic effects of the increased abundance of the invasive Round goby Neogobius melanostomus (Pallas, 1814) on network flows and trophic levels in the open coastal zone of the south-eastern Baltic Sea. Available data on biomass and diet changes were incorporated in the Ecopath with Ecosim model, which estimated non-available data. Flow changes were related to Round goby predation on Blue mussels Mytilus edulis (Linnaeus, 1758), as well as to its contribution to the diet of piscivorous groups. The model presented changes in Long-tailed duck Clangula hyemalis (Linnaeus, 1758) biomass and consumption and an increase in its trophic level. However, the results showed no changes in the trophic level of other compart-ments nor average path length, the trophic level of fishery catch or the average trophic level of the community. This demonstrates the network's ability to maintain flows within given input and retain stability under condi-tions of changes induced by an invasive species. In regards to validating the model results in the representation of the study, trophic levels estimated by the dynamic model strongly correlated to ones calculated from stable nitrogen isotope (delta 15N) ratios of consumers.