Understanding the distribution and structure of biotopes is essential for marine conservation according to international legislation, such as the European Marine Strategy Framework Directive (MSFD). ...The biotope ‘Sea Pen and Burrowing Megafuna Communities’ is included in the OSPAR list of threatened and/or declining habitats. Accordingly, the MSFD prescribes a monitoring of this biotope by the member states of the EU. In the German North Sea, however, the distribution and spatial extent of this biotope as well as the structuring of its benthic species inventory is unknown. We used an extensive geo-referenced dataset on occurrence, abundance and biomass of the benthic infauna of the south-eastern North Sea to estimate the distribution of the biotope and to characterize the associated infauna assemblages. Sediment preferences of the burrowing megafauna, comprising decapod crustaceans and echiurids, were identified and the core distribution areas of the burrowing megafauna were modelled using Random Forests. Clusters of benthic infauna inside the core distribution areas were identified by fuzzy clustering. The burrowing megafauna occurred on a wide range of sediments with varying mud contents. The core distribution area of the burrowing megafauna was characterized by elevated mud content and a water depth of 25–55 m. The analysis of the benthic communities and their relation to sedimentological conditions identified four infauna clusters of slightly varying species composition. The biotope type ‘Sea Pen and Burrowing Megafuna Communities’ is primarily located inside the paleo valley of the river Elbe and covers an area of 4980 km2. Dedicated monitoring will have to take into account the spatial extent and the structural variability of the biotope. Our results can provide a baseline for the evaluation of the future development of the environmental status of the biotope. The maps generated herein will facilitate the communication of information relevant for environmental management to authorities and policy makers.
•The distribution of an endangered benthic biotope in the SE North Sea is modelled.•Benthic communities of the muddy biotope are identified.•Analyses are based on an extensive, multi-annual dataset.•Results facilitate planning of mandatory environmental monitoring.•Maps are provided for communication of results to stakeholders.
Meiofauna play an essential role in the diet of small and juvenile fish. However, it is less well documented which meiofaunal prey groups in the sediment are eaten by fish. Trophic relationships ...between five demersal fish species (solenette, goby, scaldfish, dab <20 cm and plaice <20 cm) and meiofaunal prey were investigated by means of comparing sediment samples and fish stomach contents collected seasonally between January 2009 and January 2010 in the German Bight. In all seasons, meiofauna in the sediment was numerically dominated by nematodes, whereas harpacticoids dominated in terms of occurrence and biomass. Between autumn and spring, the harpacticoid community was characterized by Pseudobradya minor and Halectinosoma canaliculatum, and in summer by Longipedia coronata. Meiofaunal prey dominated the diets of solenette and gobies in all seasons, occurred only seasonally in the diet of scaldfish and dab, and was completely absent in the diet of plaice. For all fish species (excluding plaice) and in each season, harpacticoids were the most important meiofauna prey group in terms of occurrence, abundance and biomass. High values of Ivlev’s index of selectivity for Pseudobradya spp. in winter and Longipedia spp. in summer provided evidence that predation on harpacticoids was species-selective, even though both harpacticoids co-occurred in high densities in the sediments. Most surficial feeding strategies of the studied fish species and emergent behaviours of Pseudobradya spp. and Longipedia spp. might have caused this prey selection. With increasing fish sizes, harpacticoid prey densities decreased in the fish stomachs, indicating a diet change towards larger benthic prey during the ontogeny of all fish species investigated.
The caprellid amphipod Caprella mutica became rapidly established in the North Sea, on the west coasts of Scotland and Ireland, the Irish Sea and English Channel. The first record for C. mutica from ...Jade Bay, in the southern North Sea, is reported here. High densities exceeding three-hundred individuals per wood panel (approximately 7000 ind./m super(-2)) were found on wooden settlement panels in August/September 2009 associated with the tube-building amphipod species Jassa marmorata and Corophium acherusicum. The extensive mud-tube colonies of J. marmorata and C. acherusicum on the panels provide a suitable habitat for C. mutica attachment.
•Herring gulls prefer high bivalve biomass and low water levels for foraging.•Tracking and hydrodynamic data can be used to predict the occurrence of bivalve beds.•Herring gulls are suitable ...indicators for intertidal bivalve beds in the Wadden Sea.
Germany is an EU member state and is thus obliged to monitor and protect its marine and coastal areas in the context of international treaties (e.g. EU Marine Strategy Framework Directive, EU Natura2000 directives, Trilateral Monitoring and Assessment Programme, OSPAR) to achieve the good environmental status (GES). Suitable indicators thus need to be developed to assess the status of relevant ecosystems. Intertidal bivalve beds belong to the most productive habitats in the shallow coastal waters of the Wadden Sea but are highly dynamic and difficult to monitor. Extensive benthos and sediment sampling are required to study their development and distribution. We therefore evaluated the suitability of herring gulls (Larus argentatus) as a bioindicator species for monitoring these habitats. As flexible and opportunistic top-predators, herring gulls prefer to forage on intertidal flats and feed on bivalves (Cerastoderma edule, Mytilus edulis, Ensis leei) and crustaceans, with intertidal habitats near the breeding colony preferred during the incubation period. We used state of the art tracking devices to analyse habitat selection by herring gulls, and assessed how this was driven by biotic and abiotic factors. We then designed a habitat model to predict the occurrence of intertidal bivalve beds for directed monitoring, based on GPS logger data from herring gulls and hydrodynamic data. Both methods showed high correlations of herring gull foraging patterns with bivalve biomass and inundation time, depending on the distance from the breeding colony. The movement patterns of herring gulls clearly mirrored intertidal bivalve distributions. These results showed that combining GPS-logger data for top-predators, such as birds, with environmental data has great potential for monitoring and assessing the GES. We propose that herring gulls may be used as an indicator to locate bivalve beds in the Wadden Sea and to detect changes in the food web.
Fungus-growing termites rely on mutualistic fungi of the genus Termitomyces and gut microbes for plant biomass degradation. Due to a certain degree of symbiont complementarity, this tripartite ...symbiosis has evolved as a complex bioreactor, enabling decomposition of nearly any plant polymer, likely contributing to the success of the termites as one of the main plant decomposers in the Old World. In this study, we evaluated which plant polymers are decomposed and which enzymes are active during the decomposition process in two major genera of fungus-growing termites. We found a diversity of active enzymes at different stages of decomposition and a consistent decrease in plant components during the decomposition process. Furthermore, our findings are consistent with the hypothesis that termites transport enzymes from the older mature parts of the fungus comb through young worker guts to freshly inoculated plant substrate. However, preliminary fungal RNA sequencing (RNA-seq) analyses suggest that this likely transport is supplemented with enzymes produced in situ. Our findings support that the maintenance of an external fungus comb, inoculated with an optimal mixture of plant material, fungal spores, and enzymes, is likely the key to the extraordinarily efficient plant decomposition in fungus-growing termites.
Ecological network analysis (ENA) is an efficient tool to conduct holistic evaluation of the functioning and structure of ecosystems. ENA results can be used to support management decisions, but ...further development is needed to improve ENA application. We compared the food web functioning of three areas of the Wadden Sea: the Sylt-Rømø Bight, the Norderaue tidal basin and the Jade Bay, and present an example application of ENA indices in decision making processes. We used a sequential increase in uniform uncertainty from 50% to 99% using 10% increments to evaluate the robustness of the network comparisons. The results showed that the Jade Bay differed in its system functioning from the Sylt-Rømø Bight and the Norderaue tidal basin which represent the Northern Wadden Sea. The Jade Bay system, which is dominated by mudflats, had a heavier reliance on detritivory pathways, while the Northern Wadden Sea, which is dominated by Arenicola-sand flats, relied more on exchanges with the North Sea. Higher recycling, redundant pathways and flow diversity in the Jade Bay indicated that this system is probably more resilient against external perturbations than the Northern Wadden Sea systems which are more organized and specialized. This was related to the high standing stocks of suspension feeders in the Northern Wadden Sea, resulting from the establishment of several invasive suspension feeders, such as the Pacific oysters, the American razor clams and the common slipper shell. This study showed that 1- uncertainty analyses are crucial for the interpretation of ENA results and their use in management, 2- temporal measurable trends of indices which are robust to model uncertainty would be more appropriate for decision making than single reference values, 3- using ENA for assessment purposes in the Wadden Sea must be based on several representative sites taking into account their habitat types as well as morphological and physical characteristics, in terms of water depth, hydrodynamics and degree of enclosure of back barrier areas.
•Ecological Network Analysis (ENA) can be used to inform management decisions.•We compare ENA results of three Wadden Sea systems as an example of ENA application.•The Jade Bay, dominated by mudflat, is more resilient than the Northern Wadden Sea.•Uncertainty analyses are crucial to use ENA results in decision making.•The choice of monitored sites for management should be based on main habitat type.
Fungus-growing termites rely on mutualistic fungi of the genus
and gut microbes for plant biomass degradation. Due to a certain degree of symbiont complementarity, this tripartite symbiosis has ...evolved as a complex bioreactor, enabling decomposition of nearly any plant polymer, likely contributing to the success of the termites as one of the main plant decomposers in the Old World. In this study, we evaluated which plant polymers are decomposed and which enzymes are active during the decomposition process in two major genera of fungus-growing termites. We found a diversity of active enzymes at different stages of decomposition and a consistent decrease in plant components during the decomposition process. Furthermore, our findings are consistent with the hypothesis that termites transport enzymes from the older mature parts of the fungus comb through young worker guts to freshly inoculated plant substrate. However, preliminary fungal RNA sequencing (RNA-seq) analyses suggest that this likely transport is supplemented with enzymes produced
Our findings support that the maintenance of an external fungus comb, inoculated with an optimal mixture of plant material, fungal spores, and enzymes, is likely the key to the extraordinarily efficient plant decomposition in fungus-growing termites.
Fungus-growing termites have a substantial ecological footprint in the Old World (sub)tropics due to their ability to decompose dead plant material. Through the establishment of an elaborate plant biomass inoculation strategy and through fungal and bacterial enzyme contributions, this farming symbiosis has become an efficient and versatile aerobic bioreactor for plant substrate conversion. Since little is known about what enzymes are expressed and where they are active at different stages of the decomposition process, we used enzyme assays, transcriptomics, and plant content measurements to shed light on how this decomposition of plant substrate is so effectively accomplished.
Neobiotic species can have profound impacts on food webs and entire ecosystems. The American razor clam Ensis leei was introduced into the Wadden Sea by vessels in the late 1970s and has since spread ...widely. It has been suggested that Ensis does not interact strongly with other benthic species. The abundance and biomass of E. leei were recorded in 2393 samples in the north-eastern Wadden Sea and 800 samples in the south-eastern Wadden Sea over a total period of 9 years. Using an interdisciplinary approach, we developed a habitat prediction model using sedimentological and hydrodynamic predictors to help understand the shape of the ecological niche occupied by Ensis in the Wadden Sea. Our model showed that Ensis preferred areas with moderately high bed shear stress and prolonged or constant water coverage. Ensis preferred coarse sediments in the northern sub-area but coarse and muddy sediments in the southern sub-area and was negatively affected by the sand mason worm Lanice conchilega in the northern sub-area. Predictions of the spatial distribution of Ensis using the northern and southern datasets revealed major differences in predicted hot-spots throughout the entire study site. This study thus highlights the need to collect a sufficiently large dataset from different sub-areas of the Wadden Sea to allow valid conclusions to be drawn regarding the spatial distribution of Ensis. The negative effects of L. conchilega on Ensis abundance and biomass as well as the occurrence of Ensis in muddy sediments in the south suggest that the ecological niche of this neobiotic species is likely to overlap partly with the native fauna of the Wadden Sea.
•Long-term data were used to determine ecological niche and predict habitat potential of Ensis leei.•Abundance and biomass of Ensis were related with sedimentologic and hydrodanamic predictors.•Ensis occurred both, in coarse sediments as well as in muddy environments.•Ensis abundance and biomass declined in areas with dense Lanice conchilega reefs.•The invasive Ensis is thought to overlap with the pristine benthic fauna particularly in muddy sediments.
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