The road to success: Global dispersal and ecological footprint of the amphipod super-crustacean Jassa

10th International Crustacean Congres

Why Local Initiatives as a Driving Force for Germany’s Renewable Energy Expansion Must Reinvent Themselves.

This paper analyses the enabling conditions, barriers and future prospects of decentralised experimentation with renewable energy sources (RES) in the German energy transition, with a specific focus on the multi-level governance framework. It investigates why, and under which conditions, decentralised experiments have served as a major driving force in the development of RES in Germany, highlighting the instrumental role local governments and the national support scheme for RES have played in supporting and protecting decentralised RES initiatives. Looking at the impact of decentralised experimentation, this paper argues that the scope of decentralised renewable energy development is now such that there is an obvious need for multi-level governance coordination to address the emerging challenges of temporal and spatial disparities between power generation and demand, as well as distributional and land-use conflicts. The authors observe that many local and regional governments have not yet sufficiently considered the coordination required to make their own efforts compatible with overall energy system transition needs. They may lose their function as important facilitators for RES experimentation if they do not start engaging in new approaches to stakeholder participation, coordinated regional energy flows and system integration of RES. Moreover, bottom-up experimentation with decentralised energy system structures is also threatened by recent changes in the political framework condi-tions at the European and national level which have led to a reform of the German support scheme for RES, including, amongst others, a phase-out of the feed-in tariff scheme and its replacement by an auction scheme. Against the backdrop of these adverse political framework conditions, the paper concludes by discussing strategies to preserve the dynamics of decentralised experimentation as a vigorous driver of the German energy transition

Colonisation success of introduced oysters is driven by wave-related exposure

The Pacific oyster, Magallana gigas, is an extremely successful invader with established populations in marine and estuarine habitats almost all over the world. Ecological implications of the introduction of this species to indigenous communities are well documented. However, the processes by which this species successfully establishes in a recipient community is still insufficiently understood. The early detection of the oyster at the island of Helgoland (North Sea) provided the ideal opportunity to investigate whether physical mechanisms, such as wave exposure, influence their successful colonisation. We hypothesized that oyster colonisation benefits from wave-protected conditions. For this purpose, we evaluated colonisation success of M. gigas among wave-protected sites and wave-exposed sites along the island’s pier system. The densities of M. gigas were significantly higher at wave-protected sites than at wave-exposed sites, and the frequency distributions of oyster lengths indicated better growth and higher survival rates in the harbours. This higher colonisation success at wave-protected sites may be explained by the relative retention time of water masses in the harbours, probably resulting in both reduced larval drift and lower energy demands for secretion formation (i.e. firmer binding to the substrate). The fact that the density of M. gigas can vary greatly on small spatial scales depending on exposure corroborates a multiple exposure sampling approach to monitor oyster populations in order to avoid potential overestimations of population sizes in given areas

Low-frequency noise pollution impairs burrowing activities of marine benthic invertebrates

Sounds from human activities such as shipping and seismic surveys have been progressively invading natural soundscapes and pervading oceanic ambient sounds for decades. Benthic invertebrates are important ecosystem engineers that continually rework the sediment they live in. Here, we tested how low-frequency noise (LFN), a significant component of noise pollution, affects the sediment reworking activities of selected macrobenthic invertebrates. In a controlled laboratory setup, the effects of acute LFN exposure on the behavior of three abundant bioturbators on the North Atlantic coasts were explored for the first time by tracking their sediment reworking and bioirrigation activities in noisy and control environments via luminophore and sodium bromide (NaBr) tracers, respectively. The amphipod crustacean Corophium volutator was negatively affected by LFN, exhibiting lower bioturbation rates and shallower luminophore burial depths compared to controls. The effect of LFN on the polychaete Arenicola marina and the bivalve Limecola balthica remained inconclusive, although A. marina displayed greater variability in bioirrigation rates when exposed to LFN. Furthermore, a potential stress response was observed in L. balthica that could reduce bioturbation potential. Benthic macroinvertebrates may be in jeopardy along with the crucial ecosystem-maintaining services they provide. More research is urgently needed to understand, predict, and manage the impacts of anthropogenic noise pollution on marine fauna and their associated ecosystems

Small suspension-feeding amphipods play a pivotal role in carbon dynamics around offshore man-made structures

The establishment of artificial hard substrates (i.e. offshore wind farms and oil and gas platforms) on marine soft sediments increases the available habitat for invertebrate communities that would otherwise be restricted to natural hard bottoms. Suspension feeding invertebrates clear a significant amount of particles from the water column and release organic matter in the form of feces, influencing the basis of marine food webs and affecting surrounding environments. Artificial structures in the southern North Sea are dominated by a suspension-feeding crustacean in terms of abundance and sometimes even biomass: the amphipod Jassa herdmani. Animal densities of this tiny biofouler are known to exceed 1 million individuals per m2. Despite their small body sizes and their simple filter apparatus, we hypothesized that J. herdmani is a highly effective suspension feeder with a significant impact on neighboring communities due to its high abundances. In a feeding experiment, individuals of J. herdmani were provided with either an algal or an animal diet under two different temperature regimes. Clearance rates and fecal-pellet carbon (FPC) were measured. The results revealed high clearance rates and subsequent FPC, which were more pronounced at the higher temperature. Furthermore, clearance rates and FPC varied insignificantly with different food items. We further used the current findings for upscaling calculations to the total number of offshore windfarms and oil and gas platforms in the southern North Sea. Our calculations indicated that J. herdmani alone clears 0.33–4.71 km3 water per year in the southern North Sea. At the same time, these amphipods release 255–547 tons of carbon per year by means of defecation, thus enriching the surrounding soft sediments with organic matter. Our study highlights that tiny amphipods can mediate indirect effects of man-made structures in the North Sea, which could have a profound impact on pelagic and benthic habitats

Effects of low-frequency noise and temperature on copepod and amphipod performance

Offshore wind farms (OWF) are bound to increase as a mitigation strategy to reduce the emission of greenhouse gases, it is crucial to address all of their potential impacts on key ecosystem components in detail. Especially, the chronic effect of noise created during OWF turbine operations (duration 20-25 years) must be understood. As sensitive receptors cover the whole body of crustaceans to detect their surroundings, those low frequency noises may disrupt basic ecological (prey detection and predator avoidance) and physiological (metabolism) functions. Here we present an investigation designed to understand the joint effect of noise and increased temperature on copepod. The pelagic copepod Acartia tonsa is commonly used as a proxy for a range of fundamental processes that relate to marine planktonic crustaceans. Given that higher temperatures increase metabolic demands, the experiment was conducted at three different temperature levels (18, 21, 24°C) combined with silent and noise treatments. We assessed the combined effects on energetic balance, and oxidative stress indicators. The outputs of the project will provide important information on the potential impact of low-frequency noise on marine invertebrate key organisms with implications for secondary production and ecosystem functioning

Generalized changes of benthic communities after construction of wind farms in the southern North Sea

Over the last years, the development of offshore renewable energy installations such as offshore wind farms led to an increasing number of man-made structures in marine environments. Since 2009, benthic impact monitoring programs were carried out in wind farms installed in the southern North Sea. We collated and analyzed data sets from three major monitoring programs. Our analysis considered a total of 2849 sampling points converted to a set of biodiversity response metrics. We analyzed biodiversity changes related to the implementation of offshore wind farms and generalized the correlation of these changes with spatial and temporal patterns. Our results demonstrate that depth, season and distance to structure (soft-bottom community) consistently determined diversity indicators and abundance parameters, whereas the age and the country affiliation were significantly related to some but not all indices. The water depth was the most important structuring factor for fouling communities while seasonal effects were driving most of the observed changes in soft-sediment communities. We demonstrate that a meta-analysis can provide an improved level of understanding of ecological patterns on largescale effects of anthropogenic structures on marine biodiversity, which were not visible in single monitoring studies. We believe that meta-analyses should become an indispensable tool for management of offshore wind farm effects in the future, particularly in the view of the foreseen development of offshore renewable energies. This might lead to a better picture and more comprehensive view on potential alterations. However, this requires a modern open-source data policy and data management, across institutions and across national borders

Spotlight on coarse sediments: Comparative characterization of a poorly investigated seafloor biotope in the German Bight (SE North Sea)

Extensive marine benthos surveys have resulted in a solid understanding of the broad distribution pattern of seafloor biotopes in the southeastern North Sea (temperate northeast Atlantic region). However, due to the low spatial resolution of large-scale surveys, specific smaller-scale biotopes with scattered distribution have been insufficiently captured. Consequently, knowledge regarding the environmental characteristics and species inventories of some specific biotopes is still limited. We investigated the habitat characteristics and the macroinfauna (i.e., organisms in samples collected by a sediment grab and retained in a sieve with a mesh size of 1000 μm) of a spatially restricted, patchy coarse sediment (i.e., grain size fraction >500 μm accounting for ≥60% of the total sample mass) biotope in the German Bight over three consecutive years. Habitat and faunal characteristics were contrasted with four other benthic biotopes sampled at the same time to allow for a comparative evaluation. Our study revealed considerable fluctuations in grain size distribution among samples of the coarse sediment, potentially resulting from a frequent redistribution of sediments. A total number of 243 infauna taxa were identified at the 66 stations sampled over three consecutive years (16–33 stations per year) with a considerable proportion of endangered and rare species. The results highlight that previous studies have underestimated the species richness of the biotope. The focus on this previously poorly studied biotope type allowed us to detect species in the study region that were formerly unreported. The macro-infauna in the coarse sediments was characterized by comparatively high abundance and biomass, which may provide a rich food resource for organisms from higher trophic levels. Therefore, coarse sediments likely are an ecologically valuable seafloor biotope despite its limited coverage