Invasive species in Weddell Sea : Effects on food web structure

Abstract: The cold water of Antarctica has a unique endemic fauna, where durophagous predators are rare or absent. Due to climate change the water is heating up and the predators have begun to return to the Southern Ocean, which could bring a lot of changes to the food web. There is a high risk it will lead to losses in the unique marine fauna of Antarctica. The aim of this study is therefore to examine the potential effect these invasive species has on the food web structure in the Weddell Sea. To study this, several general network metrics were used (connectance, number of interactions, vulnerability and generality, trait distributions), as well as a number of centrality metrics (betweenness, closeness, PageRank). The analyses showed that none of the invasive species become important in the Weddell Sea food web. Nor do they significantly change the food web structure in any way which impact the importance of the native species. Their great opportunism regarding their prey species, and thereby their connectedness and thus their position in the network, are probably the main reason why theses invasive species did not become important in this food web. The lack of changes in the food web structure due to the presence of these invasive species are probably also a result of not including factors such as abundances and network dynamics in the analyses, which seem to be the driving forces when it comes to changes in food web structure caused by invasion of species.