Description: Human-induced habitat destruction, overexploitation, introduction of alien species and climate change are causing species to go extinct at unprecedented rates, from local to global scales. There are growing concerns that these kinds of disturbances alter important functions of ecosystems. Our current understanding is that key parameters of a community (e.g. its functional diversity, species composition, and presence/absence of vulnerable species) reflect an ecological network’s ability to resist or rebound from change in response to pressures and disturbances, such as species loss. If the food web structure is relatively simple, we can analyse the roles of different species interactions in determining how environmental impacts translate into species loss. However, when ecosystems harbour species-rich communities, as is the case in most natural systems, then the complex network of ecological interactions makes it a far more challenging task to perceive how species’ functional roles influence the consequences of species loss. One approach to deal with such complexity is to focus on the functional traits of species in order to identify their respective roles: for instance, large species seem to be more susceptible to extinction than smaller species. Here, we introduce and analyse the marine food web from the high Antarctic Weddell Sea Shelf to illustrate the role of species traits in relation to network robustness of this complex food web. Our approach was threefold: firstly, we applied a new classification system to all species, grouping them by traits other than body size; secondly, we tested the relationship between body size and food web parameters within and across these groups and finally, we calculated food web robustness. We addressed questions regarding (i) patterns of species functional/trophic roles, (ii) relationships between species functional roles and body size and (iii) the role of species body size in terms of network robustness. Our results show that when analyzing relationships between trophic structure, body size and network structure, the diversity of predatory species types needs to be considered in future studies.

Description: The study of ecosystem functioning – the fluxes of energy and material through biotic and abiotic components of an ecosystem – is becoming increasingly important in benthic ecological research. We investigated the functional structure of macrozoobenthic communities at four long-term sampling sites in the southern North Sea using biological traits assigned to life history, morphological and behavioural characteristics. The “typical” species of the macrofaunal assemblages at the sampling sites was characterized by small to medium body size, infaunal burrowing life style, deposit feeding habit, omnivory diet type, short to medium life span, gonochoristic sexual differentiation, 〈 2 years age at maturity, high fecundity, and planktotrophic development mode. Functional diversity differed significantly among the four sites. As part of the present study, trait information for 〉 330 macrofaunal taxa have been compiled in a comprehensive database.