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Towards resolving the submesoscale and quantifying its role in the decay of Agulhas rings
No full textFine-scale processes (1–100 km) are the most energetic features of the ocean, influencing basin-scale and global circulation. They have a major impact on heat and salt transport and water mass distribution, regulate climate-critical air-sea fluxes, and shape the biogeochemical environment and marine biome. Therefore, these processes need to be implemented in future ocean and climate models. Within the WHIRLS project, an ERC Synergy Grant, we aim to define the structure, evolution, and phenomenology of fine-scale physical and biogeochemical processes in the upper 1000 m of the water column. The focus area is the Cape Basin and the entire Agulhas Current system around South Africa, a global hotspot for mesoscale and submesoscale activity, where eddy dynamics, heat exchange, and marine productivity interact. To capture the submesoscale, we are developing a NEMO-based global model hierarchy, including high-resolution nests with horizontal grid spacing below the km-scale. Sensitivity experiments varying in the numerical representation of, e.g., tides, mixing, and advection schemes will be performed with the finest resolution configuration eINALT100 to explore the role of submesoscale processes. Furthermore, Lagrangian simulations within the OceanParcels framework with virtual particles representing water masses will be used to investigate the influence of submesoscale dynamics on the decay of Agulhas rings and the redistribution of heat and salt due to mixing processes at the ring margins
The Chromosome-level Genome of the Ctenophore Mnemiopsis leidyi A. Agassiz, 1865 Reveals a Unique Immune Gene Repertoire
No full textCtenophora are basal marine metazoans, the sister group of all other animals. Mnemiopsis leidyi is one of the most successful invasive species worldwide with intense ecological and evolutionary research interest. Here, we generated a chromosome-level genome assembly of M. leidyi with a focus on its immune gene repertoire. The genome was 247.97 Mb, with N50 16.84 Mb, and 84.7% completeness. Its karyotype was 13 chromosomes. In this genome and that of two other ctenophores, Bolinopsis microptera and Hormiphora californensis, we detected a high number of protein domains related to potential immune receptors. Among those, proteins containing Toll/interleukin-1 (TIR2) domain, NACHT domain, Scavenger Receptor Cystein-Rich (SRCR) domain, or C-type Lectin domain (CTLD) were abundant and presented unique domain architectures in M. leidyi. M. leidyi seems to lack bona fide Toll-like Receptors, but it does possess a repertoire of 15 TIR2 domain-containing genes. Besides, we detected a bona fide NOD-like receptor and 38 NACHT domain-containing genes. In order to verify the function of those domain-containing genes, we exposed M. leidyi to the pathogen Vibrio coralliilyticus. Among the differentially expressed genes, we identified potential immune receptors, including four TIR2 domain-containing genes, all of which were upregulated in response to pathogen exposure. To conclude, many common immune receptor domains, highly conserved across metazoans, are already present in Ctenophora. These domains have large expansions and unique architectures in M. leidyi, findings consistent with the basal evolutionary position of this group, but still might have conserved functions in immunity and host–microbe interaction
Glass geochemistry and tephrostratigraphy of key tephra layers in and around Lake Van, Eastern Anatolian Volcanic Province (EAVP)
No full textHighlights
• Detailed glass geochemical database of key tephra units from Nemrut and Süphan in the EAVP.
• Fourteen tephra V-layers from the AR core of Lake Van can be individually geochemically correlated to these volcanoes.
• Proximal tephra outcrops around Lake Van can be geochemically correlated to these V-layers.
• AR core resolves stratigraphic and age issues of proximal units from Nemrut, linking proximal and V-layers together.
Abstract
The volcanoes of Nemrut and Süphan in the Eastern Anatolian Volcanic Province (EAVP) are significant sources of volcanic ash (tephra), which are found in palaeoclimatic and archaeological records in the eastern Mediterranean region. However, there is sparse glass geochemistry and little known about the eruption history of these volcanoes, limiting their full tephrochronological potential. Here, we present detailed, comprehensive single-shard major, minor and trace elem geochemistry of tephra deposits sampled at new and previously studied proximal outcrops around Lake Van and fourteen visible tephra layers (V-layers) from the ICDP Ahlat Ridge (AR) core of Lake Van spanning 130 to 30 ka. The volcanic glass from the following proximal eruption units: Lower Trachytic Pumice (LT-P), Lower Trachytic Ignimbrite (LT-I), Middle Pumices, Upper Rhyolitic Pumice and Ignimbrite (UR-PI), Upper Trachytic Ignimbrite (UT-I), and the chosen V-layers were geochemically characterised. This new glass data allows new and revised previous chrono-stratigraphic correlations between the proximal units and several V-layers. Mixed rhyolitic and trachytic glasses of V-18a correlate to the UR-P and UR-I proximal tephra units, and to previously published data from the Middle Nemrut (M-NF)-O, M-NF-I, Tatvan Ignimbrite and AP-8 units. These are all from the same caldera forming eruption of Nemrut at ∼33 ka. Glasses of the older V-30 layer correlate to a Middle Pumice Unit and M-NF-R, and V-45 represents the ‘Çekmece Formation’. The trachytic glasses of V-51 correlate to LT-P, LT-I and the M-NF-Agglutinate unit erupted from Nemrut. The distinctive basaltic glasses from V-60 correlate to an eruption of İncekaya and V-64 is a newly identified eruption from the Süphan volcano. The older V-layers identified and analysed are from Nemrut based on comparing the new glass compositions to previously published whole-rock and glass data. This comparison indicates the V-75 pantelleritic tephra correlates to the dated AP-4 proximal unit. Each of these large eruptions are easily chemically differentiated using SiO2, FeOt, CaO and Al2O3. The integration of the proximal outcrops with the continuous, well-constrained Lake Van sedimentary medial record provides a detailed tephrostratigraphic record in a volcanic region where the proximal outcrop record is fragmented and confusing
Novel Field Experiment on Alkalinity Enhancement in Intertidal Environments — A Trailblazer for Natural Climate Solutions
No full textKey Points:
- Implementation of a nature-based experiment for assessment of alkalinity enhancement as a climate solution
- Enhanced weathering of mafic rocks and minerals in salt marshes
- Description of the experimental design, implementation, sampling strategy, and analytical procedures of the in situ experiment
One recently proposed approach to reduce atmospheric CO2 concentrations is marine alkalinity enhancement. This technique increases the CO2 uptake capacity of seawater through weathering of fine-grained (mafic) rocks and minerals in marine environments. The weathering process has been extensively tested in laboratory studies and verified by numerical models. Field experiments scaling the CO2 uptake under natural conditions are still lacking. In a methodological approach, a novel in situ experiment was designed and installed in a salt marsh at Ria Formosa coastal lagoon, southern Portugal. The experiment comprised deployments of different sizes of olivine and basalt substrates, and a control site, which were tidally submerged twice a day. A monthly monitoring scheme of supernatant and porewater properties from each deployment and control site was established, and procedures for temperature, salinity, oxygen, pH, total alkalinity, nutrient, and trace metal analyses were defined. This paper is devoted to the methods and describes the design, a protocol for the analyses, and an evaluation of experimental performance and reliability. Data from the first 6 months are presented for validation of the experiment. They demonstrated elevated total alkalinity in water samples, mostly in porewater after the deployments, while salinity, oxygen, and pH reflect the control conditions. Significant alkalinity differences were observed between the treatments and the natural background conditions monitored at the control site, during the 6 months of the experiment. The methodological approach is presented with strengths, limitations, and recommendations for an upscaling as CO2 removal measure, servicing, and subsequent investigations
Mixed-layer lipidomes suggest offshore transport of energy-rich and essential lipids by cyclonic eddies
No full textMesoscale eddies are ubiquitous features in the ocean affecting the cycles of nutrients and carbon. Cyclonic eddies formed in Eastern Boundary Upwelling Systems can substantially modulate primary production by phytoplankton and the vertical and lateral export of organic carbon. However, the impact of eddy activity on the biochemical composition of eukaryotic phytoplankton, bacteria and archaea and associated consequences for carbon and energy flows are largely unknown. Here, we investigated the microbial lipidome in the surface ocean in and around a cyclonic eddy formed in the coastal upwelling system off Mauritania. We show that the eddy contained almost three times the amount of lipids compared to the surrounding open-ocean and coastal waters. The eddy lipid signature with energy-rich triacylglycerols and essential fatty acid-containing membrane lipids of eukaryotic phytoplankton origin was further significantly different from the ambient waters. Strong variability in lipid distributions within the eddy was related to differences in microbial community composition. Estimates indicate that in the Mauritanian upwelling area, as much as 9.7 ± 2.0 gigagrams of lipid carbon per year is delivered to the open ocean by coastal cyclonic eddies potentially fueling higher trophic levels and contributing to the maintenance of secondary productivity and carbon export offshore
3. Wochenbericht FS Sonne Reise SO310
No full textFS Sonne Reise SO310 (S‐555),
20.02.25 – 22.03.25, Wellington – Wellington;
Quantifizierung der Rolle von Rutschungen in submarinen Canyons an aktiven und passiven Kontinentalrändern (MAWACAAP
Morphological analysis of cold-water coral skeletons for evaluating in silico mechanical models of reef-scale crumbling
No full textThe structural complexity of cold-water corals is threatened by ocean acidification. Increased porosity and thinning in structurally critical parts of the reef framework may lead to rapid physical collapse on an ecosystem scale, reducing their potential for biodiversity support. Understanding the structural-mechanical relationships of reef-forming corals is important to enable the use of in silico mechanical models as predictive tools that allow us to determine risk and timescales of reef collapse. Here, we analyze morphological variations of the branching architecture of the cold-water coral species Lophelia pertusa to advance mechanical in silico models based on their skeletal structure. We identified a critical size of five interbranch lengths that allows using homogenized finite element models to analyze mechanical competence. At smaller length scales, mechanical surrogate models need to explicitly account for the statistical morphological differences in the skeletal structure. We showed large morphological variations between fragments of L. pertusa colonies and branches, as well as dead and live skeletal fragments which are driven by growth and adaptation to environmental stressors, with no clear branching-specific patterns. Future in silico mechanical models should statistically model these variations to be used as monitoring tools for predicting risk of cold-water coral reefs crumbling
Influence of Ocean Alkalinity Enhancement on the Stability of Phytoplankton and Microzooplankton Communities
No full textThe rapid increase in anthropogenic CO₂ emissions since the Industrial Revolution has led to climate change, impacting ecosystems, seasonal patterns, and economies. To meet the 1.5°C Paris Agreement target, CO₂ emissions must be reduced, with Negative Emission Technologies (NETs) including Ocean Alkalinity Enhancement (OAE) gaining attention. OAE involves adding alkaline materials (e.g., minerals, industrial by-products) to seawater, increasing CO₂ absorption and altering ocean chemistry, potentially affecting plankton communities fundamental to marine food webs. However, its ecological impacts remain poorly understood.
This doctoral thesis examines how OAE affects phytoplankton and microzooplankton communities through two mesocosm studies and a laboratory experiment. The first study tested CO₂-equilibrated OAE in oligotrophic waters, showing no significant effects on plankton biomass, diversity, or composition, suggesting resilience and environmental safety in such conditions. The second study explored CO₂-non-equilibrated OAE with quicklime and olivine additions, revealing that, under oligotrophic conditions, phytoplankton remained unaffected. However, after nutrient enrichment, diatoms thrived, particularly in silicate-based OAE, while coccolithophores declined, highlighting potential ecosystem shifts in eutrophic waters. The third study assessed nickel (Ni) toxicity, a trace metal found in certain alkaline materials. While some phytoplankton species showed resilience, others, like diatoms, were highly sensitive, indicating that trace metals could influence community structure.
Overall, OAE appears environmentally benign under tested CO₂-equilibrated conditions, though CO2-non-equilibrated conditions and trace metal exposure may introduce ecological risks. The findings highlight the need for further research to refine OAE applications and minimize unintended consequences
Urban Environments Promote Adaptation to Multiple Stressors
No full textAnthropogenic activities have drastically changed environmental conditions worldwide, negatively impacting biodiversity and ecosystem services. At the same time, the majority of the human population lives in urban areas that are greatly altered from natural habitats. Nevertheless, many species thrive in these urban environments. To improve our knowledge of evolution and adaptation in these anthropogenically impacted habitats, we conducted the widest series of stress experiments to date with three marine taxa: one mussel and two gammarid species. We compared intraspecific populations from protected and human-altered habitats to determine their tolerance to salinity, temperature and partial pressure of CO2 in water (pCO2) regimes. Populations from impacted habitats typically outperformed protected habitat populations, with individuals from the most impacted habitat being the most robust. We propose that urban populations are adapting to life in disturbed environments—this adaptation concurrently promotes more resilient rescue populations but potentially confers increased invasion risk from non-native species
1. Wochenbericht FS Sonne Reise SO310
No full textFS Sonne Reise SO310 (S‐555),
20.02.25 – 22.03.25, Wellington – Wellington;
Quantifizierung der Rolle von Rutschungen in submarinen Canyons an aktiven und passiven Kontinentalrändern (MAWACAAP