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Submarine ash megabed fed by far-traveled, shoreline-crossing pyroclastic currents from a large explosive volcanic eruption
No full textLarge explosive volcanic eruptions from island volcanoes deliver vast quantities of ash to the marine environment. While many of the transport pathways are understood, those from shoreline-crossing or submarine pyroclastic currents, and their transformation into water-supported gravity flows, remain poorly constrained. We report the discovery by International Ocean Discovery Program (IODP) deep drilling of a 200-meter-thick ash megabed buried in rift basins of the South Aegean Volcanic Arc. The >73–cubic kilometer ash deposit originates from the Kos Plateau Tuff caldera-forming eruption, which occurred 161 thousand years ago, >120 kilometers to the east. The ash forms a chemically uniform, graded megabed lacking bioturbation, interpreted as having been emplaced by a stream of eruption-fed turbidity currents. Bioclastic debris within the ash provides evidence of widespread destruction of marine ecosystems. Large volcanic eruptions can remodel the seafloor landscape, deposit thick ash turbidites, and destroy marine biota on island arc–wide scales in short-lived, catastrophic events
Quantifying the role of mass wasting in submarine canyons on active and passive margins, Cruise No. SO310, 20.02.25 - 22.03.25, Wellington (New Zealand) - Wellington (New Zealand), MAWACAAP
No full textSubmarine canyons incise active and passive continental margins around the world. They are
highly dynamic submarine systems that form complex seafloor structures. Canyon head and flank
failures often progress upslope to form retrogressive terraces. Usually located in close proximity
to populated areas, such canyon failures pose a potential threat to settlements and submarine
installations. The main objective of RV SONNE Cruise SO310 was to analyse and directly
compare canyon formation and modification processes in different tectonic settings. The working
area off New Zealand provides the opportunity to compare canyons in different settings (active
and passive margins) in close proximity. Hydroacoustic as well as 2D and 3D seismic data were
collected in the Palliser Canyon region. The data reveal an active canyon with hardly any recent
undisturbed sedimentary deposits in the thalweg area. Numerous landslides were imaged along the
canyon walls, potentially showing a connection to a well-developed gas hydrate system. OBS were
deployed for a full-waveform inversion experiment to characterise weak layers. Cores were taken
for dating and geotechnical investigations of the landslides. Pegasus Canyon was investigated
using seismic and hydroacoustic surveys, as well as sediment sampling. The data reveal an
abundance of landslides of various ages and sizes along the canyon's flanks. Stacked landslide
deposits and contouritic-like deposits were found in the thalweg region of the canyon. The
evolution of the canyon is influenced by a prominent fault system
FESOM2.1-REcoM3-MEDUSA2: an ocean–sea ice–biogeochemistry model coupled to a sediment model
No full textThis study describes the coupling of the process-based Model of Early Diagenesis in the Upper Sediment with Adaptable complexity (MEDUSA version 2) to an existing ocean biogeochemistry model consisting of the Finite-volumE Sea ice–Ocean Model (FESOM version 2.1) and the Regulated Ecosystem Model (REcoM version 3). Atmospheric CO2 in the model is a prognostic variable which is determined by the carbonate chemistry in the surface ocean. The model setup and its application to a pre-industrial control climate state is described in detail. In the coupled model, 1390 PgC is stored in the top 10 cm of the bioturbated sediment, mainly as calcite, but also as organic matter (10 %). In the coupled simulation, atmospheric CO2 stabilizes at ∼295 ppm after 2000 years, in line with the CO2 level expected from the climate forcing conditions. Sediment burial of carbon, alkalinity, and nutrients in the coupled simulation is set to be compensated by riverine input. The spatial distribution of biological production is altered depending on the location of riverine input and reduction in sedimentary input, as well as the strength of local nutrient limitation, while the global productivity is not affected substantially. With this coupled ocean–sediment system the model is able to simulate the carbonate compensation feedback under moderate perturbation of CO2 in the atmosphere
Early Triassic origin of coccolithogenesis
No full textCalcareous nannofossil investigations were conducted on Lower and Middle Triassic marine successions from South China. Coccoliths, nannoliths and calcispheres are relatively frequent and moderately preserved, showing an increase in diversity from the Smithian (Olenekian) to the Ladinian. The oldest nannofossils, dated to the Smithian, include Eoconusphaera hallstattensis and very simple coccoliths attributed to a sp. A morphogroup. Nannoliths of Prinsiosphaera triassica and Carnicalyxia, along with rare specimens of Tetralithus pseudotrifidus and Crucirhabdus cf. C. minutus are present in the Spathian-Pelsonian (Olenekian-Anisian) and Longobardian (Ladinian) samples, respectively. A total of 10 new morphotypes are also described. The Smithian coccoliths documented here significantly narrow the temporal gap between molecular clock estimates for the origin of calcifying coccolithophores and their first fossil record. Our data represent the oldest known nannofossils and push back the onset of coccolithophore calcification by approximately 40 million years, shortly after the end-Permian mass extinction. The Olenekian primitive, simple and tiny coccoliths from South China suggest that early coccolithophores emerged in a coastal environment of the eastern Tethys Ocean. The onset of calcification in Calcihaptophycidae may have been facilitated by suppressed atmospheric CO2 levels, coupled with increased nutrient availability following the emplacement of the Siberian Traps. The emergence of this new phytoplanktonic group correlates with the earliest recovery of benthic calcifiers, potentially shaping post-extinction marine biodiversity and influencing the evolution of the ocean toward modern conditions
The immeasurable value of plankton to humanity
No full textPlankton, a diverse group of aquatic organisms, make Earth livable, regulate aquatic life, and provide benefits to human societies such as access to clean water, food security, and well-being. They also support economies and inspire biotechnological innovations. This article aims to raise awareness of the value of plankton to humanity and serves as an informative guide for aquatic professionals, policymakers, and anyone interested in plankton. We present the value of plankton across six themes of human interest: biogeochemistry; ecology; climate; the evolution of science; economy; and culture, recreation, and well-being. Guided by the 2022 Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services values assessment, we introduce the six themes under the Life Framework of Values to offer a comprehensive summary of the significance of plankton to humanity. In addition, we provide examples of plankton variables used in policy frameworks and recommendations for enhancing understanding of their value through long-term sustainable research and monitoring
Paleo-communities across the mesophotic to deep zones of the Terrible and Nameless Banks, The Sicily Channel, Central Mediterranean
No full textExploring the genomic and physiological basis of adaptation to seasonal variation in the copepod Eurytemora affinis
No full textDiurnal Oceanic Thermal Variability in the Atlantic Cold Tongue: Dependence on Wind Speed and Background Conditions
No full textKey Points:
- Specially programmed Argo floats capture the vertical extent of the diurnal warm layer under varying winds in the equatorial Atlantic
- In May–June (cold tongue onset), diurnal warming extends deeper and faster and the turbulent heat flux through the mixed layer is stronger
- Higher winds enhance the vertical heat flux associated with the diurnal warm layer; shear and stratification modulate its vertical extent
Diurnal ocean mixing processes in the equatorial Atlantic play a crucial role in shaping surface temperature and velocity, thereby influencing air-sea interactions and the vertical heat transport. However, characterizing the upper ocean diurnal variability remains challenging due to its high vertical and temporal variability and limited observations, resulting in uncertainties in ocean model skills. Between March and July of 2021 and 2022, 10 specially programmed Argo floats were deployed to sample the diurnal cycle in the equatorial Atlantic at high temporal (3-hourly) and vertical (meter-scale) resolution. Combined with mooring data, the observations revealed that weaker winds in March–April were associated with a shallower and slower (1.8 m/hr) vertical extension of the diurnal warm layer, compared to May–June corresponding to the seasonal onset of the cold tongue, when the deepening rate reached 3.2 m/hr. The comparison of the observations with a regional model demonstrates that the model reproduces most features of the observed diurnal warm layer but underestimates its vertical extension and deepening rate. The model is then used to show that the diurnal vertical heat flux through the mixed layer increases by 50% from weak to strong wind conditions. However, oceanic background conditions also play a significant role, as similar mean wind speeds can result in vertical heat fluxes that reach twice the depth and intensity at 10°W compared to 0°. This study emphasizes the need to better capture diurnal variability to assess its impact on the Atlantic cold tongue and its representation in models
Non-native species in the Philippines and Southeast Asia
No full textNon-native species introductions threaten global biodiversity, ecosystems, and the services they provide. The limited capacity of developing countries to mitigate and manage biological invasions increases their vulnerability to the resulting impacts. Developing countries' lack of comprehensive information on non-native species to help formulate sound management efforts is a key challenge. Here, we provide the most comprehensive national list of established non-native species in the Philippines, along with an update on the Southeast Asian region to aid national and regional efforts in addressing the threats posed by biological invasions. Our assessment indicates that the Philippines currently hosts at least 1,029 established non-native species, the highest number among Southeast Asian countries, amidst a total of 2,528 non-native species established in the region. A taxonomic breakdown showed species of the division Tracheophyta and phylum Chordata to be the majority of established non-native species in the Philippines, most of which are found in terrestrial ecosystems. A network analysis further highlighted a high degree of similarity in the composition of established non-native species among Southeast Asian countries, with the Philippines' non-native species community most closely resembling that of Indonesia, likely due to close socio-economic ties and similar climatic niches and environmental conditions. Finally, we identified 1,499 non-native species established in Southeast Asia but not the Philippines, which may pose potential future threats for the country. We highlight the need for more comprehensive research on established non-native species in the Philippines and the Southeast Asian region, particularly taxonomic studies and research at broader geographic scales, to better understand the distribution and impact of these species and stress the critical need to address this transboundary threat