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 Collector's App is a platform-independent (macOS, Linux and Windows) software written in Python. The Collector's App allows biological data to be quality-checked and stored in CRITTERBASE, which is a science-driven PostgreSQL data warehouse for marine biota. For further data processing and statistical analyses or modelling purposes, the respective data can be queried directly via SQL from your CRITTERBASE data warehouse.

Description: The following downloadable R scripts for calculating the repeated accessibility are available here: 1. "Download of daily sea ice raster" - The R script automatically downloads all GeoTiffs from IUP, University of Bremen, and saves them in the directory of your choice. 2. "Existing and missing data" - The R script uses the downloaded GeoTiffs to create a table showing for which days satellite images are available and for which days they are not. 3. "Information of GeoTiffs" - The R script extracts important metadata of the downloaded GeoTiffs such as geographical projection, spatial extent and maximum value. A metadata table is created. 4. "Repeated accessibility" - The R script performs the repeated accessibility calculation based on a selectable threshold of sea ice concentration.