Alfred Wegener Institute for Polar and Marine Research
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The Local Turn in a Global Sea: Identifying Sustainability Trade‐Offs in Regionalized Marine Aquaculture Systems
Get PDFMarine aquaculture, like the broader seafood industry, relies heavily on international trade and global supply chains for both production and sales. Recent global disruptions, including the COVID-19 pandemic, the Russian invasion of Ukraine, the conflicts in the Middle East, and trade tensions, have exposed the social and economic vulnerabilities inherent in a globalized production system. In response, these events have sparked growing interest in transitioning to localized and regional supply chain models. Calls to “buy national” and support domestic economies highlight this trend toward regionalization. This study explores the sustainability implications of regionalizing marine aquaculture by examining the four key segments of the supply chain. These are (1) upstream inputs and resources (2) aquaculture production (3) downstream added value-processing and (4) distribution–transportation. Potential benefits of regional production models include increased resilience to disruptions, lower transportation-related carbon emissions, and support for local economies. However, such models may also introduce trade-offs, including reduced production efficiency, supply and sales limitations, and implications for social, cultural, and governance structures. Our analysis reveals that the sustainability outcomes of regionalization are complex and context-dependent. It is influenced by the specific characteristics of existing supply chains and the regional contexts in which they operate. While regionalization may offer advantages in certain contexts, it does not guarantee improved sustainability. Thus, it is crucial to critically assess the assumption that regionalization inherently leads to improved sustainability outcomes. Proactive evaluation of these dynamics is essential to develop strategies that maximize benefits while addressing potential trade-offs
Following a half-century oceanographic data gap in the northern Canadian Arctic Archipelago: multidecadal variability of the Pacific water throughflow
Get PDFThe Canadian Arctic Archipelago (CAA) serves as a major conduit between the Arctic Ocean and the North Atlantic. The Nansen Sound fiord system, which encapsulates Nansen Sound, Greely Fiord, Eureka Sound and several surrounding fiords, forms the northernmost oceanographic passageway through the CAA. Due to hostile ice conditions, the area has been understudied since the original oceanographic surveys were conducted in the 1960s and 1970s. The historic data highlighted a very weak signal of the relatively fresh Pacific-derived water (PW). Here, we present new oceanographic observations, including PW tracers, and contrast them against the historic data. Salinity profiles taken in 2024 show significant freshening as compared to 1976. This freshening is attributed to enhanced presence of PW in the area. We suggest that changes in the Arctic Oscillation impact the export gateways of PW from the Arctic Ocean, with the recent switch to a positive phase enhancing the outflow of cool and less saline PW through the CAA. Overall, this provides a first glimpse into variability of the freshwater flow through the straits of the northern CAA.</jats:p
Influence of Transient Bottom Water Temperature Variations on Geothermal Heat Flow Measurements From the Bellingshausen Sea, West Antarctica, and the Baltic Sea
Get PDFAbstract Geothermal heat flow (GHF) data provide important constraints for ice‐sheet flow dynamics as GHF affects sliding conditions at the ice‐bed contact and englacial temperatures. However, marine measurements of the geothermal gradients can get distorted down to ∼3–10 m below seafloor by annual bottom water temperature variations. First‐ever geothermal data from the Bellingshausen Sea shelf, West Antarctica, are presumably affected by temperature variations in the modified Circumpolar Deep Water (mCDW) over annual and multidecadal periods. As magnitude and resolution of temperature data are low in the Bellingshausen Sea, we test a 1D water‐sediment model on Baltic Sea data, which includes long‐term water temperature and semiannual GHF measurements. The model approximates the measured sub‐bottom temperatures satisfactorily, although sparse data in Antarctica lead to uncertainties in reconstructed bottom water temperatures. Distortions in the geothermal gradients of the Bellingshausen Sea can be modeled using annual water temperature variations of ±0.03–0.15°C. However, the spatial heterogeneity of mCDW temperatures, recorded by heat flow lance sensors, shows no connection to geothermal gradient distortions. Therefore, the mCDW temperature variations are likely not strongly seasonal but are local changes of similar magnitude. Higher‐resolution water temperature records are needed to quantify uncertainties through annual water temperature variations in the current measurement‐derived GHF of 47–84 mWm −2 in Ronne Entrance and 21–57 mWm −2 in Eltanin Bay. Multidecadal ocean warming reduces the geothermal gradient by 16%–55% in the Bellingshausen Sea and leads to a reversed geothermal gradient in the Baltic Sea. This highlights the need to correct marine GHF for environmental factors.
Plain Language Summary Geothermal heat flow provides important constraints for ice‐sheet flow dynamics as it affects the sliding conditions at the ice‐bed contact and the temperature profile of the ice. However, subseafloor temperature gradients can be distorted down to 3–10 m below seafloor due to the annual variations in water temperature. First‐ever geothermal data from the Bellingshausen Sea could be affected by temperature variations in the modified Circumpolar Deep Water (mCDW) over annual and multidecadal periods. A vertical 1‐D model including water and sediment temperatures was tested on Baltic Sea data, as these contain a 66‐year bottom water temperature time series and semiannual subseafloor temperatures. Model outcomes for the Bellingshausen Sea demonstrate that water temperature variations of ±0.03–0.15°C can explain the observed distorted geothermal gradients. Spatial analysis of the mCDW indicates that these water variations are likely local temperature variations and not a clearly defined seasonal water temperature signal. The model shows that uncertainties in measured geothermal gradients of the Bellingshausen Sea cannot be resolved due to low‐resolution annual water temperature data, and thus, uncertainties remain in heat flow estimates of 21–84 mWm −2 . Additionally, bottom water warming recorded over the last decades further contributes to a reduction in the measured geothermal gradient.
Key Points Marine geothermal heat flow (GHF) modeling shows the limit of reconstructing bottom water and sediment temperature variations in data‐sparse areas First GHF measurements in the Bellingshausen Sea show temperature signals of local bottom water variations Climate change has reached the seafloor temperature gradients of the Baltic Sea and the Bellingshausen Sea (West Antarctica
High Inter- and Intraspecific Variability in Amphidinol Content and Toxicity of Amphidinium Strains
Get PDFAmphidinols (AM) are a diverse group of bioactive polyketides produced by dinoflagellates of the genus Amphidinium, known for their hemolytic, antifungal, and cytotoxic activities. This work presents the assessment of AM profiles in a comprehensive number of strains, whose species boundaries were previously established through detailed taxonomic analysis. Using UHPLC-MS/MS, we characterized the spectrum of AM analogs in 54 Amphidinium strains isolated from diverse geographical locations. In addition, toxicity was assessed using brine shrimp assays, which revealed significant inter- and intraspecific variability. Despite the broad diversity in AM content, no clear correlation was observed between total AM levels and toxicity across all strains. Multivariate analysis grouped the strains into clusters distinguished by distinct AM profiles and toxicity levels, suggesting that AM production alone does not predict toxicity. Our findings highlight the complexity of Amphidinium bioactivity, emphasizing the influence of strain-specific factors and other bioactive compounds. This work highlights the importance of integrating chemical, genetic, and biological assessments to understand better the factors that govern toxicity in this genus, with implications for ecological studies and the monitoring of harmful dinoflagellates
Twice the global average carbon burial efficiency in the Helgoland Mud Area of the North Sea: Insights into carbon sequestration in small-size depocenters on sand-dominated shelves
Get PDFContinental shelves are integral to the global carbon cycle, yet uncertainties persist about the nature and extent of carbon burial, particularly in sand-dominated areas. In the sand-dominated North Sea, the Helgoland Mud Area (HMA) emerges as a small-size mud depocenter, surrounded by sandy sediments that do not accumulate organic carbon (OC) and are separated from adjacent rivers. Such small-size depocenters, common on high-energy shelves, have underexplored OC degradation and burial efficiencies due to their limited individual size. Since sandy sediments with interspersed small-size depocenter cover ∼50 % of global shelves, these depocenters may collectively offer greater OC burial capacity than previously recognized. This study investigated the composition, degradation, and sequestration of OC from terrestrial (OCterr) and marine (OCmar) sources in surface sediments of the HMA and adjacent sandy areas using bulk (mean grain size, OC content, loading and 13C isotope composition) and molecular (fatty acids and alkanes) analyses. Our results, derived from a two end-member mixing model based on δ13C values of bulk OC, revealed that OCterr dominates (∼74 %) the sedimentary OC in both areas, with OCmar contributing ∼26 %. The HMA exhibited OCterr and OCmar contents ∼5 times higher than in the sandy areas. Both OCterr and OCmar loadings negatively correlated with mean grain size, indicating reduced OC degradation in muddy sediments. Molecular analysis further revealed that OCterr in the HMA is less refractory compared to adjacent sandy regions. These differences are attributed to differences in porewater transport, oxygen penetration depths and exposure times, all of which influence OC preservation, despite the important role of mineral protection. OCterr and OCmar accumulation fluxes in the HMA were calculated at (6.75 ± 0.61) × 10−3 and (2.54 ± 0.68) × 10−3 Tg C/yr, respectively, representing 34.3 % of OCterr export from adjacent rivers and 2.8 % of net OCmar production in the HMA. These values are twice the global average for shelf areas, highlighting the exceptional efficiency of the HMA as a carbon sink and hinting at the significance of small-size depocenters within sandy areas in the global carbon cycle
High-energy systems are underrepresented in global porewater studies of sandy beach aquifers
Get PDFAquifers beneath sandy beaches act as land-ocean conduits for groundwater and are active biogeochemical reactors modifying chemical fluxes across the land-sea interface. Subterranean estuaries of high-energy beaches with large tidal and wave amplitudes could be particularly reactive due to the exchange of large seawater volumes and transport of marine derived constituents deep into the subsurface. In this study, we first present a new classification for coastal energy regimes as a function of mean tidal range and mean significant wave height and define the term “high-energy”. We establish a global distribution map of coastal energy regimes and classify porewater study sites in sandy beach aquifers related to their prevalent energy regime. Despite their extensive contribution to the global shoreline, the porewater biogeochemistry of high-energy environments is largely unknown. Through a of the few existing porewater studies at high-energy beaches we reveal patterns in morphology, hydrology, and biogeochemistry, describe promising research strategies, and highlight future research avenues in these challenging environments
A taxonomically reliable DNA barcode reference library for North Sea macrobenthos
Get PDFEU directives (e.g. MSFD, Habitats Directive), along with OSPAR guidelines, mandate sustainable marine resource management across national borders. Benthic organisms are crucial for assessing marine ecosystem health, but their morphological identification is time-consuming and costly. High-throughput sequencing, particularly DNA metabarcoding, offers an alternative. However, DNA-based monitoring requires substantial investment in high-quality DNA reference libraries. The GEANS project (Genetic Tools for Ecosystem Health Assessment in the North Sea Region) aimed to develop efficient DNA-based tools for benthic biomonitoring. GEANS created a curated DNA reference library (COI) for species relevant to North Sea macrobenthos monitoring, using new sequences, non-public barcode sequences, and mined sequences from GenBank and BOLD. The library, stored in a dedicated BOLD project with photographs and metadata, includes DNA barcodes for 4005 specimens from 715 species, representing over 29% of North Sea macrobenthos species. Arthropoda is the most represented, while Bryozoa and Annelida have the lowest coverage. This DNA library is expected to facilitate fast, cost-effective environmental health assessments in the North Sea for public authorities and academics
Network Flow Methods for NMR-Based Compound Identification
Get PDFIn this work, we introduce a novel method for compound identification in mixtures based on nuclear magnetic resonance spectra. Contrary to many other methods, our approach can be used without peak-picking the mixture spectrum and simultaneously optimizes the fit of all individual compound spectra in a given library. At the core of the method, a minimum cost flow problem is solved on a network consisting of nodes that represent spectral peaks of the library compounds and the mixture. We show that our approach can outperform other popular algorithms by applying it to a standard compound identification task for 2D 1H,13C HSQC spectra of artificial mixtures and a natural sample using a library of 501 compounds. Moreover, our method retrieves individual compound concentrations with at least semiquantitative accuracy for artificial mixtures with up to 34 compounds. A software implementation of the minimum cost flow method is available on GitHub (https://github.com/GeoMetabolomics-ICBM/mcfNMR)
Dynamics of organic matter in algal blooms on the Greenland ice sheet
Get PDFSurface melting supports the development of pigmented algal blooms on the Greenland Ice Sheet, decreasing albedo and further accelerating melting. The interplay between carbon-fixing algae and carbon-respiring heterotrophic microorganisms ultimately controls the amount and composition of organic matter (OM) and thus the ice and snow color. Yet, the dynamics of microbially-derived OM on the Greenland Ice Sheet remain unclear. To address this knowledge gap, we incubated in situ algae-dominated snow and ice samples under light and dark conditions and characterized the changes in dissolved and particulate OM (DOM and POM) with the help of ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry. We show that glacier ice-algae habitats are dominated by highly unsaturated and aromatic compounds resistant to bio- and photo-degradation. In contrary, snow-algae habitats are enriched in bioavailable and more photosensitive unsaturated aliphatics and sulfur- and phosphorus-containing compounds. In both habitats, light exposure increased water-soluble DOM compounds derived from POM, which accounted for ~ 50–70% of the initial DOM composition. Of the initial DOM, 35–50% were heterotrophically degraded in the dark, while light alone photodegraded 6–16%. The significant accumulation of light-absorbing aromatics from POM and DOM at the end of the ice-algae experiments, underscore the greater impact of glacier ice-algae habitats on altering glacier color and accelerating melting
Summary of taxonomy changes ratified by the International Committee on Taxonomy of Viruses (ICTV) from the Bacterial Viruses Subcommittee, 2025.
Get PDFThis article summarises the activities of the International Committee on Taxonomy of Viruses Bacterial Viruses Subcommittee, detailing developments in the classification of bacterial viruses. We provide here an overview of all new, abolished, moved and renamed taxa proposed in 2024, approved by the Executive Committee, and ratified by membership vote in 2025. Through the collective efforts of 74 international contributors of taxonomy proposals in this round, 43 ratified proposals have led to the creation of one new phylum, one class, four orders, 33 families, 14 subfamilies, 194 genera and 995 species. These proposals mark significant progress in refining the taxonomy of bacterial viruses. Key updates include the creation of new orders and families that include existing taxa to better reflect genomic and evolutionary relationships. As sequencing and bioinformatics approaches continue to advance, further expansion and refinements in viral taxonomy can be anticipated in the coming years