Description: To determine the spatial resolution of sediment properties and benthic macrofauna communities in acoustic backscatter, the suitability of four acoustic seafloor classification devices (single-beam echosounder with RoxAnn and QTC 5.5 seafloor classification system, sidescan sonar with QTC Swathview seafloor classification, and multi-beam echosounder with QTC Swathview seafloor classification) was compared in a study area of approx. 6 km2 northwest of the island of Helgoland in the German Bight, southern North Sea. This was based on a simple similarity index between simultaneous sidescan sonar, single-beam echosounder and multi-beam echosounder profiling spanning the period 2011–2014. The results show a high similarity between seafloor classifications based on sidescan sonar and RoxAnn single-beamsystems, in turn associated with a lower similarity for the multi-beam echosounder system. Analyses of surface sediment samples at 39 locations along four transects (0.1 m2 Van Veen grab) revealed the presence of sandy mud (southern and western parts), coarse sand, gravel and cobbles. Rock outcrops were identified in the north-eastern and eastern parts. A typical Nucula nitidosa–Abra alba community was found in sandy muds to muddy sands in the northern part, whereas the southern part is characterised by widespread occurrence of the ophiuroid brittle star Amphiura filiformis. A transitional N. nitidosa–A. filiformis community was detected in the central part. Moreover, the southern part is characterised by a high abundance of A. filiformis and its commensal bivalve Kurtiella bidentata. The high number of A. filiformis feeding arms (up to ca. 6,800 per m2) can largely explain the gentle change of backscatter intensity along the tracks, because sediment composition and/or seafloor structures showed no significant variability.

Description: Benthic oxygen and nitrogen fluxes were quantified within the years 2012 to 2014 at different time series sites in the southern North Sea with the benthic lander NuSObs (Nutrient and Suspension Observatory). In situ incubations of sediments, in situ bromide tracer studies, sampling of macrofauna and pore water investigations revealed considerable seasonal and spatial variations of oxygen and nitrogen fluxes. Seasonal and spatial variations of oxygen fluxes were observed between two different time series sites, covering different sediment types and/or different benthic macrofaunal communities. On a sediment type with a high content of fine grained particles (o63 mm) oxygen fluxes of �15.5 to �25.1 mmol m�2 d�1 (June 2012), �2.0 to �8.2 mmol m�2 d�1 (March 2013), �16.8 to �21.5 mmol m�2 d�1 (November 2013) and �6.1 mmol m�2 d�1 (March 2014) were measured. At the same site a highly diverse community of small species of benthic macrofauna was observed. On a sediment type with a low content of fine grained particles (o63 mm) high oxygen fluxes (�33.2mmol m�2 d�1 August 2012; �47.2 to �55.1 mmolm�2 d�1 November 2013; �16.6 mmol m�2 d�1 March 2014) were observed. On this sediment type a less diverse benthic macrofaunal community, which was dominated by the large bodied suspension feeder Ensis directus, was observed. Average annual rain rates of organic carbon and organic nitrogen to the seafloor of 7.44 mol Cm�2 y�1 and 1.34 mol N m�2 y�1 were estimated. On average 79% of the organic bound carbon and 95% of the organic bound nitrogen reaching the seafloor are recycled at the sediment–water interface. & 2015 Elsevier Ltd. All rights reserved

Description: The present compilation is the first attempt to generate a comprehensive list of all macrozoobenthic species recorded at least once in the German regions of the North Sea and Baltic Sea including non-indigenous species and freshwater species which occurred in brackish waters (estuaries, bays, fjords etc.). Based on the data of several research institutes and consultancies, the macrozoobenthic species inventory comprises a total of 1.866 species belonging to 16 phyla including 193 threatened species. The most common groups were: malacostracan crustaceans (21%), Polychaeta (19%), and Gastropoda (12%). Even though the two major marine regions are separated by only 50 km of land, the composition of the respective communities was different. The two seas shared only 36.6% of the recorded species which should have profound and far-reaching consequences for conservation purposes. Considering all macroinvertebrates listed 96 species, or the equivalent of 5.2%, were introduced mainly during the last two centuries. Both seas are heavily affected by human activities and are sensitive to climate change displayed by effects on the faunal compositions. The present checklist is an important step to document these changes scientifically and may act as a base for political and management decisions.

Description: 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.

Description: There is growing evidence that climate change could affectmarine benthic systems. This review provides information of climate change-related impacts on the marine benthos in the North Atlantic. We cover a number of related research aspects, mainly in connection to two key issues. First, is the relationship between different physical aspects of climate change and the marine benthos. This section covers: (a) the responses to changes in seawater temperature (biogeographic shifts and phenology); (b) altered Hydrodynamics; (c) ocean acidification (OA); and (d) sea-level rise-coastal squeeze. The second major issue addressed is the possible integrated impact of climate change on the benthos. This work is based on relationships between proxies for climate variability, notably the North Atlantic Oscillation (NAO) index, and the long-term marine benthos. The final section of our review provides a series of conclusions and future directions to support climate change research on marine benthic systems.

Description: 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.