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Current research revealed distinct changes in ecosystem functions, and thus in ecosystem stability and resilience, caused by changes in community structure and diversity loss. Benthic species play an important role in benthic-pelagic coupling, such as through the remineralization of deposited organic material, and changes to benthic community structure and diversity have associated with changes in ecosystem functioning, ecosystem stability and resilience. However, the long-term variability of traits and functions in benthic communities is largely unknown. By using abundance and bioturbation potential of macrofauna samples, taken along a transect from the German Bight towards the Dogger Bank in May 1990 and annually from 1995 to 2017, we analysed the taxonomic and trait-based macrofauna long-term community variability and diversity. Taxonomic and trait-based diversity remained stable over time, while three different regimes were found, characterised by changes in taxonomic and trait-based community structure. Min/max autocorrelation factor analysis revealed the climatic variables sea surface temperature (SST) and North Atlantic Oscillation Index (NAOI), nitrite, and epibenthic abundance as most important environmental drivers for taxonomic and trait-based community changes.

Identifying patterns in the effects of temperature on species' population abundances could help develop a general framework for predicting the consequences of climate change across different communities and realms. We used long-term population time series data from terrestrial, freshwater and marine species communities within central Europe to compare the effects of temperature on abundance across a broad range of taxonomic groups. We asked whether there was an average relationship between temperatures in different seasons and annual abundances of species in a community, and whether species attributes (temperature range of distribution, range size, habitat breadth, dispersal ability, body size and lifespan) explained interspecific variation in the relationship between temperature and abundance. We found that, on average, warmer winter temperatures were associated with greater abundances in terrestrial communities (ground beetles, spiders and birds) but not always in aquatic communities (freshwater and marine invertebrates and fish). The abundances of species with large geographical ranges, larger body sizes and longer lifespans tended to be less related to temperature. Our results suggest that climate change may have, in general, positive effects on species’ abundances within many terrestrial communities in central Europe while the effects are less predictable in aquatic communities.

The joint research project WIMO (Wissenschaftliche Monitoringkonzepte für die Deutsche Bucht/Scientific Monitoring Concepts for the German Bight, NE North Sea) aims at providing methods for detection and analysis of seabed habitats using modern remote sensing techniques. Our subproject focuses on hydroacoustic techniques in order to gain information about seafloor environments and sediment dynamics. In a timeframe of four years, several key areas in the German Bight were repeatedly observed using different hydroacoustic gear (i. e. sidescan sonars, single/multibeam echo sounders and sub-bottom profilers). In order to ground-truth the acoustic data, hundreds of grab samples and underwater videos were taken. With these techniques it is possible to distinguish between different seafloor habitats, which range from muddy to sandy seafloors (esp. near the barrier islands) to rugged or vegetated/populated reefs around Helgoland. The conducted monitoring program revealed seasonal changes regarding the abundance of the sand mason worm (Lanice conchilega) and the brittle star (Amphiora filiformis) as well as ongoing sedimentary processes driven by tidal currents and wind/storms. It was also possible to determine relationships between sediment characteristics and benthos in some key areas. An essential part of our project included a comparison between the datasets obtained with different hydroacoustic devices, configurations, and evaluation methods in the same study areas. The investigation reveals that there could be distinct differences in interpreting the data and hence in the determination of prevailing seafloor habitats, especially in very heterogeneous areas and at transition zones between the habitats. Therefore, it is recommended to employ more than one hydroacoustic system (preferably a singlebeam device combined with a wide-swath sonar system) synchronously during a survey in order to gain more reliable and detailed information about the seafloor environments. The results of this project study form an important contribution to ongoing and future projects, in particular with regard to the technical configuration of the sonar systems, the workflows concerning post-processing and validation of the hydroacoustic data as well as the monitoring concepts that were worked out. However, a full automation of these workflows is not feasible. For the time being, measurements, post-processing and data evaluation still need supervision and expert knowledge.

Invasive species are a general issue common of every seas in the world. Impacts of biological invasion on the food web of the Wadden Sea will be figure out through 3 related positions (Sarina Jung, PhD student ; Camille de la Vega, PhD student ; Ulrike Schueckel, Post doctoral student) included in the INFOWEB project. To investigate the impact of invasive species on the food web, a good comprehension of the trophic relation and energy fluxes between the different compartments of the food web is essential. Food webs will be portrayed for three different parts of the Wadden Sea (Jade Bay, Sylt-Römö Bight, Balgzand) using Ecological Network Analysis and the influence of invasive species on trophodynamics will be estimated. Different habitats homing different species communities have been already described, for examples, “Arenicola flat”, “sea grass bed” or “mussel bed”. According to these habitats, several models will be built. The first steps of these three studies will be to collect the missing data needed to build the model: biomass, respiration, egestion, production and diet composition for each species or compartments of the food web. The diet composition will be estimated with the method of stable isotopes coupled for the high trophic level with stomach content analysis.