Alfred Wegener Institute for Polar and Marine Research
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From science to policy: evolving marine biodiversity targets
Full text linkThe Montreal‐Kunming Global Biodiversity Framework (GBF) substantially advances biodiversity protection. We systematically reviewed the scholarly literature published during the UN Decade on Biodiversity (2010–2020) to assess whether GBF targets align with scientific approaches and improve upon the Aichi Targets in recognizing the complexity of marine biodiversity. Our findings showed that the new targets have improved to address the full suite of essential biodiversity variable (EBV) classes, reducing the risk of changes in crucial aspects of biodiversity being overlooked. We observed a high degree of alignment between research and policy in EBVs and a relative increase in the reliance of the GBF on secondary variables such as ecosystem function. While this alignment mirrors that within other global frameworks, we caution against overemphasizing secondary variables at the expense of foundational variables such as community composition. Our analysis demonstrates that global policy targets align well with scientific understanding of marine biodiversity. Future efforts should focus on improving national‐level implementation and refining indicators to foster transformative change in biodiversity conservation
The interference of anthropogenic low-frequency sounds with gammarid and corophiid amphipods
Full text linkArctic Ocean virus communities and their seasonality, bipolarity, and prokaryotic associations
Full text linkViruses of microbes play important roles in ocean environments as agents of mortality and genetic transfer, influencing ecology, evolution and biogeochemistry. However, we know little about the diversity, seasonality, and host interactions of viruses in polar waters. Here, we study dsDNA viruses in the Arctic Fram Strait across four years via 47 long-read metagenomes of the cellular size-fraction. Among 5662 vOTUs, 98% and 2% are Caudoviricetes and Megaviricetes, respectively. Viral coverage is, on average, 5-fold higher than cellular coverage, and 8-fold higher in summer. Viral community composition shows annual peaks in similarity and strongly correlates with prokaryotic community composition. Using network analysis, we identify putative virus-host interactions and six ecological modules associated with distinct environmental conditions. The network reveals putative novel cyanophages with time-lagged correlations to their hosts (in late summer) as well as diverse viruses correlated with Flavobacteriaceae, Pelagibacteraceae, and Nitrosopumilaceae. Via global metagenomes, we find that 42% of Fram Strait vOTUs peak in abundance in high latitude regions of both hemispheres, and encode proteins with biochemical signatures of cold adaptation. Our study reveals a rich diversity of polar viruses with pronounced seasonality, providing a foundation for understanding viral regulation and ecosystem impacts in changing polar oceans
Genomic diversity and adaptation in Arctic marine bacteria.
Full text linkArctic marine bacteria experience seasonal changes in temperature, salinity, light, and sea ice cover. Time-series and metagenomic studies have identified spatiotemporal patterns in Arctic microbial communities, but a lack of complete genomes has limited efforts to identify the extent of genomic diversity in Arctic populations. We cultured and sequenced the complete genomes of 34 Arctic marine bacteria to identify patterns of gene gain, loss, and rearrangement that structure genomes and underlie adaptations to Arctic conditions. We found that the most abundant lineage in the Arctic (SAR11) is comprised of diverse species and subspecies, each encoding 50-150 unique genes. Half of the 16 SAR11 genomes harbor a genomic island with the potential to enhance survival in the Arctic by utilizing the osmoprotectant and potential methyl donor glycine betaine. We also cultured and sequenced four species representing an uncultured family of Pseudomonadales, four subspecies of Pseudothioglobus (SUP05), a genus of high GC Puniceispirillales (SAR116), and a family of low GC SAR116. Time-series 16S rRNA amplicon data indicate that this culture collection represents up to 60% of the marine bacterial community in Arctic waters. Their genomes provide insights into the evolutionary processes that underlie bacterial diversity and adaptation to Arctic waters.IMPORTANCEGenetic diversity has limited efforts to assemble and compare whole genomes from natural populations of marine bacteria. We developed a cultivation-based population genomics approach to culture and sequence the complete genomes of bacteria from the Arctic Ocean. Cultures and closed genomes obtained in this study represent previously uncultured families, genera, and species from the most abundant lineages of bacteria in the Arctic. We report patterns of gene gain, loss, rearrangement, and adaptation in the dominant lineage (SAR11), as well as the size, composition, and structure of genomes from several other groups of marine bacteria. This work demonstrates the potential for cultivation-based high-throughput genomics to enhance understanding of the processes underlying genomic diversity and adaptation
The Amazonian mangrove systems accumulate and release dissolved neodymium and hafnium to the oceans
Full text linkMangroves are essential tropical ecosystems nurturing a wide range of marine biodiversity and counteracting global warming by sequestering atmospheric carbon dioxide. Hence, the export mechanisms and fluxes of particulate and dissolved organic carbon and trace elements from mangroves directly influence coastal productivity, the global carbon cycle and thus global climate, which are, however, not well constrained. Here we find consistent radiogenic neodymium and hafnium isotopic compositions of porewater, sedimentary iron-manganese oxyhydroxides and coastal seawater, suggesting that the Amazonian mangrove belt supplies trace elements through porewater discharge, dissolution of iron-manganese oxyhydroxides and their interactions with seawater. Together, these processes supply 8.4 × 106 g yr-1 dissolved neodymium, equivalent to 64% of the total sources of neodymium to the Amazonian coastal seawater. Globally, mangrove systems along the continental margins contribute 6–9% of the net neodymium input to the ocean, which is similar to the contributions from atmospheric deposition. A contribution of this magnitude is potentially also the case for other trace elements, given the strong correlations between neodymium and iron (Pearson r = 0.92), and manganese (r = 0.75) concentrations across the entire river-ocean section, emphasizing the crucial role of mangrove system inputs in micro-nutrient cycling
Extraction Strategies for Profiling the Molecular Composition of Particulate Organic Matter on Glacier Surfaces
Full text linkPigmented microalgae thrive on supraglacial surfaces, producing "sticky" extracellular polymeric substances that combine into a mineral-organic matrix. Together, they enhance snow and ice melting by lowering the albedo. Understanding the chemical nature of particulate organic matter (POM) in this matrix is crucial in assessing its role in supraglacial carbon dynamics. We evaluated POM complexity in alga-rich snow and ice samples containing 0.3-6.4 wt % organic carbon (OC) via extractions with solvents of varying polarity, pH, and OM selectivity. Extraction yields were evaluated by OC analysis of the extracts, and the composition of extracted OM was analyzed using ultrahigh-resolution mass spectrometry. Individual hot water (HW), hydrochloric acid (HCl), and sodium hydroxide (NaOH) extractions achieved up to 87% efficiency, outperforming sequential, organic solvent-based extractions (<11%). OM extracted by HW, HCl, and NaOH combined had more molecular formulas (2827) than OM extracted with organic solvents (1926 formulas). Combined HW, NaOH, and HCl extractions yielded an OM composition with unsaturated, highly unsaturated, aromatic, and N-containing compounds, while unsaturated aliphatics and black carbon-derived polycyclic aromatics were enriched in the organic solvent extracts. This molecular profiling provides the first comprehensive insights into supraglacial POM composition, opening the window for understanding its role in the cryospheric carbon cycle
Arctic surface snow interactions with the atmosphere: Spatio-temporal isotopic variability during the MOSAiC expedition
Full text linkSnow on sea ice is crucial in moderating sea ice and atmosphere interactions, yet fully grasping snow’s isotopic composition and the processes shaping it presents substantial challenges, including sublimation and wind redistribution. This study utilizes a year of stable water isotope datasets from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2019/2020 to explore the complex interactions between snow deposition processes and postdepositional changes affecting snow on Arctic sea ice including seasonal and spatial dynamics. We compare snow data with water vapor isotope measurements by examining 911 individual snow isotope measurements and integrating these discrete snow samples with continuous water vapor isotope data. Autumn shows a pronounced δ18O offset between snow and vapor. In winter, δ18O and d-excess in surface snow and water vapor diverge sharply, indicating kinetic fractionation under extremely cold temperatures as research vessel Polarstern drifted from the Siberian to the Atlantic Arctic. While water vapor δ18O responds rapidly to air temperature and humidity changes, surface snow δ18O values are modulated by postdepositional processes like sublimation and wind redistribution. We found that these 2 processes play a key role in isotopic enrichment that is intensified by the snow’s prolonged surface residence. Wind-driven snow redistribution, occurring during 67% of the winter period, leads to an average surface snow δ18O of −22‰ across the sea ice by redistributing and mixing fresh snow with more metamorphosed snow. This study provides new insights into how wind-driven redistribution and prolonged surface residence not only alter isotopic values in surface snow but also obscure seasonal isotopic patterns, complicating the interpretation of snow isotope records in the Arctic. Our research to understand the differences between the isotopic values of vapor and the isotopic values of snow provides insight into interactions between snow and the atmosphere, as well as the processes that alter isotopic values internally within the Arctic snowpack. Our study highlights the complexity of surface snow isotope geochemistry across the Arctic from the eastern to the central basin during the MOSAiC expedition window and how the underlying processes of water vapor transport, temperature–isotope relations, and the role of secondary processes, including wind redistribution and sea ice formation all contribute to the horizontal and vertical geochemistry patterns
MUSICA: Multi-scale Sea Ice Coupled Analysis: Anisotropic biophysical coupling of sea ice processes
Full text linkInfluence of snowpack characteristics on winter soil temperatures (Qeqertarsuaq, Kalaallit Nunaat)
Full text linkSeasonal snow cover plays a critical role in regulating Arctic soil temperatures, particularly in permafrost landscapes. Its insulating properties depend not only on snow depth but also on snow density and stratigraphy. However, these characteristics remain poorly understood in Arctic environments due to limited availability of high-resolution measurements. This thesis investigates how spatial variability in snow depth and snow density influences soil temperatures (6 cm) during late winter in a Low Arctic maritime tundra landscape on Qeqertarsuaq (Disko Island), Kalaallit Nunaat (Greenland). The study combines high-resolution snowpack data collected with the SnowMicroPen (SMP) in April 2024 with hourly soil temperature records from 14 temperature sensors. Snow depths at the sensor locations ranged from 0.16 m to 1.10 m (mean: 0.56 m), while snowpack densities varied between 247 kg m−3 and 409 kg m−3. Average soil temperatures from October 2023 to June 2024 spanned from −4.67 °C to −0.23 °C across the site. To capture the relationship between snow cover characteristics and soil temperatures, and to assess spatial variability and uncertainty, I used Bayesian hierarchical modeling. The results how that snow depths greater than approximately 0.5 m effectively insulate the soil by dampening the impact of air temperature fluctuations, reinforcing the snowpack’s role as a thermal buffer. I also observed a positive, though more uncertain, relationship between snow density and soil temperature, suggesting that denser snow may reduce insulating capacity. These findings indicate that snow density plays an important role in Arctic ground thermal regimes, but additional high-resolution observations and further model development are needed to better quantify its effects
Insight into origin and transformation of dissolved organic matter under contrasting nutrient conditions on the Northern Patagonian Continental Shelf, Southwestern Atlantic Ocean
No full textThis study analyzed the composition and optical properties of dissolved organic matter (DOM) in the Northern Patagonian Continental Shelf (Southwestern Atlantic Ocean), which embraces highly diverse hydrographic, biological and biogeochemical regimes. The main aim was to identify autochthonous and allochthonous sources of DOM, its bulk molecular characteristics and bioavailability, in relation to contrasting regional nutrient and circulation patterns. In the coastal sector at depths ≤ 50 m, only a moderate riverine input of DOM and nutrients was detected, yet high values of the humification index (HIX) pointed to a continental origin of aromatic DOM, with sediment resuspension significantly contributing dissolved humic carbon, silicate and phosphate. In the middle shelf, high dissolved organic carbon and chlorophyll levels coincided with low bacterial carbon production (BCP) and HIX values, indicating an autotrophic production of aliphatic DOM. This was supported at the outer shelf and shelf break by nitrate input from the Malvinas Current and in the middle shelf by potentially regenerated ammonium . In the shelf break, humic- and protein-like fluorescent DOM maxima were likely originated from phytoplankton lysates, as suggested by high tryptophan-like fluorescence signals. The variation of the biological activity index (BIX) was only partially explained by chlorophyll, while BCP patterns did not. There is evidence of a site-dependent compositional artifact in the BIX values due to a background of high-BIX, recalcitrant DOM, possibly aromatic low-molecular weight peptides. Wind-driven shifts in surface circulation influenced the distribution of DOM, nutrients, and temperature, highlighting their role in the region’s annual spring bloom and future DOM dynamics studies. Overall, the results indicate a transition from terrestrially influenced, humic-rich DOM in coastal waters to predominantly autotrophic, protein-like DOM offshore, driven by nutrient availability and wind-modulated circulation. This pattern underscores the key role of physical forcing in shaping DOM sources and transformation across the Northern Patagonian Shelf