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Monitoring benthic plumes, sediment redeposition and seafloor imprints caused by deep-sea polymetallic nodule mining
No full textA deep-sea (4500 m) trial of a pre-prototype polymetallic nodule collector with independent scientific monitoring revealed that a gravity current formed behind the collector channeled through steeper seafloor sections and traveled 500 m downslope. The prevailing bottom currents dominated sediment dispersion up to the end of the monitoring area at 4.5 km distance. The maximum suspended particle concentration recorded 50 m from mining lanes was up to four orders of magnitude higher than ambient values but decreased rapidly with increasing time, distance, and altitude. Most of the plume remained close to the seafloor, with the highest concentrations at 1 m monitoring altitude and reaching background concentrations at 50 m. Rapid particle flocculation was followed by fast and substantial sediment redeposition. A mm-scale photogrammetric seafloor reconstruction allowed quantitative estimates of the thickness of redeposited sediment next to mining lanes of approximate to 3 cm and a minimum erosional depth of 5 cm
Stable and radiogenic strontium isotopes trace the composition and diagenetic alteration of remnant glacial seawater
No full textA remnant of glacial seawater preserved in the pore fluids of sediment cores from the Maldives Inner Sea provided an opportunity to investigate the stable strontium isotopic composition (δ88/86Sr) of the ocean during the Last Glacial Maximum and explore the usefulness of δ88/86Sr as a tracer of early marine diagenesis. We used paired measurements of δ88/86Sr and radiogenic Sr isotope ratios (87Sr/86Sr) in pore fluids and surrounding carbonate sediments to constrain the diagenetic history of the preserved glacial water mass at IODP Sites U1466 and U1468. These pore fluid profiles document variability in δ88/86Sr in a shallow marine setting, revealing distinct diagenetic processes dominating within different depth intervals. We find evidence for isotope fractionation during secondary calcite precipitation at intermediate depths and observe that in aragonite-dominated settings, fractionation during recrystallization may be obscured by the dissolution of aragonite in the uppermost sediments. Correcting for the effect of carbonate recrystallization on pore fluid Sr concentration ([Sr]) and isotopic composition, we estimate that glacial seawater [Sr] was higher (∼98μM) and δ88/86Sr lower (∼0.32‰) compared to the modern ocean, consistent with hypotheses attributing the present-day disequilibrium of the ocean Sr budget to glacial/interglacial changes in shelf carbonate weathering and burial. Our results provide evidence that the ocean [Sr] and δ88/86Sr are sensitive to carbon cycle changes on timescales much shorter than its residence time (∼2 Myr) and demonstrate that pore fluid δ88/86Sr measurements are a useful addition to multi-tracer studies of diagenesis in complex marine systems
Significant contribution of the unicellular cyanobacterium UCYN-B to oceanic nitrogen fixation
No full textDinitrogen (N2) fixation by diazotrophs forms a critical control on ocean productivity, yet our understanding of the distribution, abundance and activity of these microorganisms is informed by observations with limited geographical coverage. Here we show that the unicellular N2-fixing cyanobacterium, UCYN-B, drives high N2 fixation rates in the western North Pacific. Defining the ecological niche of UCYN-B using our new observations in combination with existing global diazotroph datasets allowed prediction of additional and previously unrecognized UCYN-B-dominated N2 fixation hot spots throughout large, unsampled swathes of the global ocean. Collectively, these regions potentially contribute 10.8-15.0 Tg N yr−1 to global marine N2 fixation, suggesting a pivotal role for UCYN-B in the regulation of the marine nitrogen inventory and therefore ocean productivity
Stop neglecting the blue! The relevance of One Ocean Health for the planet we want
No full textOne Health, Planetary Health, and EcoHealth – there are myriad conceptual frameworks for expanding discussions to move beyond human, animal and plant health, to be inclusive for the health of ecosystems. At present, however, despite its crucial role in the survival of our world, the ocean receives insufficient consideration within these frameworks. Therefore, greater emphasis should be placed on what can be coined One Ocean Health. To this end, we relate the health of the ocean to currently dominant connotations of the concept of health and acknowledge the ocean’s nature as one gigantic, interconnected ecosystem; a common, irreplaceable ocean on which all living things depend, human and non-human, terrestrial and aquatic alike. Recognizing the interconnectedness of ocean and society, and drawing on concepts from medical theory, we advocate for a holistic, co-developed approach to ocean health that integrates not only scientific and policy perspectives but also acknowledges the cultural diversity in the ways in which people relate to the ocean and engage with it. To achieve this, objective and subjective perspectives of what constitutes “diseases” in marine ecosystems need to be considered, while also defining means and normative goals of a “healthy ocean” – always bearing in mind the fact that this is not an end in itself, but remains crucial for the preservation of the planet that we as humans
Ground Motions, Infrasound Signals, and Seismic Velocity Perturbations: Environmental Impacts of the Rock Avalanche Induced by the 2025 Mw 6.5 Jan Mayen Strike-slip Earthquake
No full textThe Jan Mayen Island (JMI) is an activate volcano located in Arctic Ocean, at the Jan Mayen transform fault (JMTF). On 10 March 2025, a strong strike-slip Mw 6.5 earthquake occurred in the JMTF, with the fault rupturing for ~40 km long and crossing the north zone of the JMI, indicating the potential for local hazard effects. Local GNSS sensors indicated that JMI moved ~2.4 cm in WNW-ESE direction during the rupture process, corroborating with the ESE rupture direction identified by apparent duration of regional P-waves (1700-2200 km away), and the local epicenter distribution of the >1500 relocated aftershocks. The epicenter of the mainshock was located ~8 km away from Kjerulf Glacier, a long flowing glacier on the outer crater edge of the Beerenberg stratovolcano. An infrasound array located in northern Norway identified a signal arriving ~3 min after the mainshock, with the source of the signal coming with back-azimuth in direction of the Kjerulf Glacier. Additionally, the ambient seismic noise cross-correlation of three local stations, located ~3-16 km distance from the glacier, revealed subsurface velocity perturbations during ~30 min and starting ~3 min after the mainshock. Using Sentinel-2 and high-resolution MAXAR satellite images, we confirmed that the infrasound signal and seismic noise perturbations were generated by a large volume (2.8 − 6.3x105m3) of basaltic rock that detached and collapsed in the slope located in south wall of the Kjerulf Glacier, minutes after the mainshock occurred. The collapse triggered a rock avalanche that scattered debris along the glacier surface and covered most of the ice toward the border of the sea. It may take several years before the glacier surface covered with rock material returns to its previous state. Therefore, in addition to highlighting the synergy of geophysical, remote sensing, and satellite data in characterizing complex submarine fault slipping, this multidisciplinary study shows that earthquakes along oceanic transform faults can pose serious natural hazards through secondary effects, such as large rock avalanches in the land area near the epicenter
Genomic and physiological mechanisms underpinning seasonal adaptation in the copepod Eurytemora affinis
No full textEvaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea
No full textOcean alkalinity enhancement (OAE) is a climate mitigation strategy aimed at increasing the ocean's capacity to absorb and store atmospheric CO2. The effect of OAE depends significantly on local physical and biogeochemical conditions, underscoring the importance of selecting optimal locations for alkalinity addition. Using a regional coupled physical-biogeochemical-carbon model, we examine OAE responses in the North Sea, including CO2 uptake potential, enhanced carbon storage and cross-shelf export, and the associated changes in the carbonate chemistry. Alkalinity is continuously added as a surface flux in three distinct regions of the North Sea. Our simulations show that the Norwegian Trench and the Skagerrak serve as sinks for added alkalinity, reducing its interaction with the atmosphere. Alkalinity addition along shallow eastern coasts results in a higher CO2 uptake efficiency (∼0.79 mol CO2 uptake per mol alkalinity addition) than offshore addition in ship-accessible areas (∼0.66 mol CO2 uptake per mol alkalinity addition) as offshore alkalinity is more susceptible to deep-ocean loss. Long-term carbon storage, measured by excess carbon accumulation in deep ocean and cross-shelf export below permanent pycnoclines, is similar across the three scenarios and accounts for less than 10 % of total excess CO2 uptake. The smallest changes in pH occur when alkalinity is added offshore with effects nearly an order of magnitude lower than alkalinity addition in the shallow German Exclusive Economic Zone where pH increases from 8.1 to 8.4. The model's resolution (∼4.5 km in coastal areas) limits its ability to capture rapid, localized carbonate responses, leading to a nearly 10-fold underestimation of chemical perturbations. Thus, finer-scale models are needed to accurately assess near-source alkalinity impacts
7. Wochenbericht SO314
No full textForschungsfahrt des FS SONNE SO 314: T-SECTOR Southeast Pacific Rise: 13.08.2025 (Papeete/Tahiti) – 05.10.2025 (Antofagasta/Chile)
7. Wochenbericht: 22.09.-28.09.202