Impact of invasive species
Invasive species can have major effects on the structure and functioning of coastal ecosystem food webs through competition, altering predator-prey relationships, nutrient cycling and the structure and magnitude of energy flows between the different trophic compartments. To assess the impact of invasive species on the food web in the Wadden Sea, three intertidal areas (Jade Bay, Sylt-Rømø Bight, Balgzand) are analysed and compared by means of Ecological Network Analysis (ENA). These areas differ in the species and abundance of invasive species and in environmental conditions such as geomorphology, hydrology and sedimentology.
Compiling food web models
To compile the different food web models, the INFOWEB team (AWI, Senckenberg, NIOZ and RUG) estimates biomass, respiration, ingestion (including diet composition), egestion, production for the dominant fauna and flora communities occurring in the different habitats within these areas (e.g. lugworm-sandflats, mudflats, seagrass and mussel beds). The diet composition is estimated using stable isotopes, coupled with stomach content analysis for higher trophic levels. Temporal changes within each study area are quantitatively assessed by repetitive ENA analysis during different periods (when invasive species abundance was low and high).
Because of the uniform terminology, symbols and indices, the ENA results allows a temporal and spatial comparison of the consequences of invasive species for Wadden Sea food webs which can also be useful information for future ecosystem management concepts.