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Impact of glacial cycles and tectonics on crustal accretion revealed through spectral analysis of seafloor morphology
No full textHelmholtz Doctoral Award 2024 in the field of Earth and Environment
No full textAwarded by the Helmholtz Association in the research field of Earth and Environment (Track A
Abyssal seafloor as a key driver of ocean trace-metal biogeochemical cycles
No full textTrace elements and isotopes (TEIs) are important to marine life and are essential tools for studying ocean processes. Two different frameworks have arisen regarding marine TEI cycling: reversible scavenging favours water-column control on TEI distributions, and seafloor boundary exchange emphasizes sedimentary imprints on water-column biogeochemistry. These two views lead to disparate interpretations of TEI behaviours. Here we use rare earth elements and neodymium isotopes as exemplar tracers of particle scavenging11 and boundary exchange. We integrate these data with models of particle cycling and sediment diagenesis to propose a general framework for marine TEI cycling. We show that, for elements with greater affinity for manganese oxide than biogenic particles, scavenging is a net sink throughout the water column, contrary to a common assumption for reversible scavenging. In this case, a benthic flux supports increasing elemental concentrations with water depth. This sedimentary source consists of two components: one recycled from elements scavenged by water-column particles, and another newly introduced to the water column through marine silicate weathering inside sediment. Abyssal oxic diagenesis drives this benthic source, and exerts a strong influence on water-column biogeochemistry through seafloor geometry and bottom-intensified turbulent mixing. Our findings affirm the role of authigenic minerals, often overshadowed by biogenic particles, in water-column cycling, and suggest that the abyssal seafloor, often regarded as inactive, is a focus of biogeochemical transformation
Evaluating the effect of amoxicillin treatment on the microbiome of Orbicella faveolata with Caribbean yellow band disease
No full textHost microbiomes play a key role in coral disease dynamics; thus, it is essential to characterize microbial communities of diseased tissues and identify how they are altered by potential treatments, especially as coral reef populations continue to decline globally. The abundance of Orbicella faveolata, a major reef-building Caribbean coral species, has significantly declined due to several stressors, including infectious disease. Caribbean yellow band disease (CYBD) often results in complete colony mortality. We applied an amoxicillin-laced Base2B ointment to CYBD lesion areas on O. faveolata within Buck Island Reef National Monument, St. Croix, USVI, trying to halt disease progression. Another CYBD lesion area on the same colony served as a paired untreated control. Microbiomes of the apparently healthy tissue adjacent to the treatment were characterized pretreatment and 2 days post-treatment, along with the paired untreated CYBD controls and nearby healthy colonies. Both microbiomes of untreated CYBD lesions and apparently healthy tissue on CYBD colonies had a significantly higher alpha diversity and significantly differed from those of nearby healthy colonies, suggesting potential systemic effects of CYBD. Amoxicillin treatment significantly changed the microbial community composition of tissues adjacent to the treatment site. The relative abundance of the bacterial family Vibrionaceae, a putative pathogen for CYBD and often associated with other coral diseases, was enriched post-treatment. However, the lesion progression rates of treated and untreated lesion areas were similar. Our results suggest that amoxicillin may disrupt the microbiome of adjacent tissue on O. faveolata, allowing for opportunistic Vibrio sp. bacteria to colonize, and may not be an effective treatment for CYBD.IMPORTANCEOrbicella faveolata, a primary reef-building coral species in the Caribbean, has been severely impacted by Caribbean yellow band disease. This disease causes tissue loss, which often culminates in the complete loss of the colony since recovery is rarely observed. The present study is significant because the development of an effective long-term treatment for Caribbean yellow band disease and understanding how the microbial partners contribute to pathogenesis are essential for conserving Caribbean coral reefs. While treatment with amoxicillin was not effective, our study uncovered valuable insights into the microbial composition of Caribbean yellow band disease in O. faveolata. In addition, this study highlights the possible unintended negative effects of treatment with amoxicillin and casts doubt on Vibrionaceae as the culprit of this disease
Cost-Effective Manufacturing of Fiber Reinforced Polymer Springs for Continuum Robots
No full textThe exploration of deep-sea environments requires specialized equipment capable of operating under extreme conditions. Traditional suction sampling systems are often used in combination with heavy and expensive equipment, limiting their accessibility for widespread research purposes. To address this, we present a novel design for a suction sampling system that leverages the concept of continuum robots to enhance maneuverability and reduce system weight and cost. Unlike continuum robots that utilize traditional coil springs, our design integrates custom-manufactured Fiber Reinforced Polymer (FPR) springs, effectively minimizing metallic components and achieving significant weight reduction. Notably, FRP springs offer enhanced corrosion resistance in deep-sea environments compared to metal springs. This paper outlines the conceptual development of a continuum robot and discusses the advantages of using FRP springs over traditional metal springs. It presents a cost-effective and simplified manufacturing process for producing FRP springs. Preliminary testing indicates that FRP springs have the potential to serve as a viable and accessible alternative to conventional metal springs in the design of a deep-sea continuum robot
Low Heat Flow in the Anhydros Basin, Aegean Sea, Recorded by Deep Subsurface Temperatures
No full textSubseafloor in situ temperatures in a drilled hole in the Anhydros Basin, Aegean Sea, measured during International Ocean Discovery Program (IODP) Expedition 398, yielded a low heat flow (<0.023 W/m 2 ) despite active magmatism and rifting in the region. The coldest and highest temperatures were 13.9°C at 52.5 m below seafloor (mbsf) and 15.5°C for the deepest measurement at 360.4 mbsf, respectively. Comparison of a heat transfer model with measurements suggests that sea bottom temperatures during the last glacial period were up to 10°C cooler than Holocene temperatures. The magnitude of Holocene warming co‐varies with the geothermal heat flow: if the former goes up the latter goes up. Low heat flow may arise from lateral removal of heat through deeper formations by gravity driven advection of fluids. Tectonic separation of the northwestern Anhydros Basin from the Christiana‐Santorini‐Kolumbo volcanic field may lead to minimal magmatic influences on heat flow.
Plain Language Summary
Temperatures in Earth's crust reveal the processes that create and transport heat. In the rifting Anhydros Basin in the Aegean Sea, north of the active South Aegean Volcanic Arc, International Ocean Discovery Program Expedition 398 measured cold subsurface temperatures in a borehole to depths exceeding 300 m below the seafloor. These temperatures record low heat flow and cold seafloor temperatures from the last glacial period. The low heat flow at shallow depths may be due to deeper fluid circulation that removes heat. Low heat flow further implies that there are no magma bodies within the crust in the northwestern part of the Anhydros Basin.
Key Points
Heat flow is low in the Anhydros Basin, Aegean Sea
Ocean bottom temperatures were cold during the last glacial
Subsurface temperature records surface temperature changes and heat flo
Record Warmth and Unprecedented Drop in Equatorial Atlantic Sea Surface Temperatures in 2024
No full textFrom February to March 2024, the equatorial Atlantic experienced its highest sea surface temperatures in at least 40 years. This extreme warm event was triggered by a favorable combination of El-Niño-induced westerly wind anomalies in the western equatorial Atlantic and Rossby wave reflection at the western boundary, leading to an exceptionally strong downwelling Kelvin wave. The warm event was extinguished abruptly around May by a locally-forced upwelling Kelvin wave, causing an unprecedented rapid transition to a cold phase which lasted until August. The cold event did not fully develop into an Atlantic Niña due to weak Bjerknes feedback, warming from surface heat fluxes, and thermocline deepening due to a series of equatorial wave reflections. Nevertheless, the cold event is consistent with a northward shift of the intertropical convergence zone, increased rainfall over West Africa, Sahel, and Sahara, reduced rainfall over the Gulf of Guinea, and an earlier onset of the West African monsoon.
Key Points:
- In 2024, equatorial Atlantic sea surface temperature swung unprecedentedly fast from an extreme warm event in boreal spring to a moderate cold event in summer
- The genesis, evolution and demise of these events were dominated by a unique sequence of equatorial waves combined with air-sea processes
- The equatorial cold event is consistent with heavy rainfall over West Africa and Sahara, and an earlier onset of the West African monsoo
Development of Metadata Standards for 3D Seismic and Active Source Ocean Bottom Seismometer Data
No full textThe reuse of marine seismic data requires standardised metadata. MetaSeis is the follow-up of a successfully completed similar project for two-dimensional multichannel seismic reflection raw data, conducted in collaboration with the DAM (German Marine Research Alliance) Underway Research Data initiative within the NFDI4Earth framework. The goal of MetaSeis is to develop and test metadata standards for three-dimensional seismic data and ocean bottom seismometer recordings of controlled seismic events. These events typically involve shots using airguns, as opposed to the passive recordings of earthquake seismicity that were addressed in the former HMC project eFAIRs. The first phase of the MetaSeis project involves two main tasks. First, we have adapted the two-dimensional seismic metadata standard for use with three-dimensional data, incorporating the added complexities of more extensive navigation data. This revised standard was initially tested during the R/V Maria S. Merian voyage MSM132, refined, and then reapplied during R/V Sonne voyage SO310. Further modifications are still required to accommodate the more complex data acquisition processes used by the Bundesanstalt für Geowissenschaften und Rohstoffe. Additionally, we are examining the latest industry standards to investigate if they are suitable for the scientific community. Second, MetaSeis assessed the status of legacy ocean bottom seismometer data at Alfred Wegener Institute and developed a workflow for archiving these data using a future metadata standard. In parallel, a separate standard is being developed for newly acquired ocean bottom seismometer data. The project aims to streamline the archiving of new three-dimensional reflection seismic and active-source ocean bottom seismometer data and to make these datasets more accessible for big data applications
Direct effects of ocean alkalinity enhancement in the Baltic Sea–results from in-silico experiments
No full textTo achieve carbon neutrality, ocean alkalinity enhancement (OAE) is currently being researched as a marine option for carbon dioxide removal (CDR). The approach of releasing calcite near the sediments and using the effect of enhanced mineral solubility in the pore water for more efficient dissolution may be promising in the Baltic Sea. The Baltic Sea is considered a potential application site for this method, as, in contrast to other seas, it is partly undersaturated in calcite even at shallow depths. However, the possible implications of this method, specifically if applied in coastal settings, are still poorly understood. Therefore, using a coupled hydrodynamic and biogeochemical ocean model of the Baltic Sea, we simulated the release of calcite near the sediment as a possible strategy for OAE. Simulations were run with and without enhanced solubility in the pore water for two release locations, one in shallow coastal water and one in a deep basin. While enhanced solubility by oxic mineralisation did not make a difference for the deep basin, it substantially changed the achievable calcite dissolution rates at the coastal site and therefore the potential CO2 removal. Here, our simulations provide a lower and an upper limit of the effectiveness of calcite dissolution. The release locations differed considerably in magnitude and timescales of CO2 uptake. As the saturation level of calcite appears to be the main limiting factor of the method, the CO2 removal potential of a release location cannot be upscaled infinitely by adding more calcite. Our results demonstrate a potential for OAE using calcite in the Baltic Sea. We used the model results on average and maximum changes in alkalinity and pH to reflect on potential environmental impacts based on a review of the existing literature. However, safe and responsible deployment of this CDR method in the Baltic Sea requires further research on localized dissolution rates, the alkalinity budget of the Baltic Sea and the environmental implications of OAE using calcite
