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We discovered seafloor features such as bacterial mats and carbonate crusts typical for active methane seeps on the continental slope southwest of Svalbard. These features are associated with two main northwest-southeast trending morphological structures that are oriented parallel to the regional continental slope. Both structures occur at c. 800 m water depth, at the boundary between the Storfjorden trough mouth fan to the south and the Hornsund trough mouth fan to the north, which suggests a loading related fluid seepage. The main structure displays depressions and ridges forming a crater in its center. Other occurring features include small sediment mounds, domes often covered by bacterial mats, and hummocky seafloor colonized by siboglinid tubeworms. Free gas bubbles were spotted close to the centre and plumes along the rims of the structure. Thick carbonate crusts indicate a long seepage history in the center of the structure and on top of the ridges. The sources of the seeps are likely to be Miocene old organic-rich deposits, or Paleocene hydrocarbon reservoirs. [ABSTRACT FROM AUTHOR]

Climate change and anthropogenic stressors affect the distribution, abundance, and diversity of fish communities across the world. To understand rapidly changing biotic communities, resource managers need a method to quickly and efficiently document temporal and spatial changes in community assemblages across various spatial scales. In this study, we describe the use of new video lander tools to survey fish communities in rocky marine habitats on the continental shelf and slope in California, USA. We evaluate how fish diversity metrics determined by video surveys vary among geographically distinct areas. Our results demonstrate that species diversity, evenness, and richness vary spatially across the coast. Furthermore, community assemblages differ at both broad and fine spatial scales because of differences among habitats. Length frequencies and densities of species in this study were similar to those reported in previous studies. As community assemblages and biodiversity metrics shift in response to changing stressors, it is increasingly important to develop tools and methodologies to detect and rapidly monitor these changes. [ABSTRACT FROM AUTHOR]

Widespread hypoxia occurs seasonally across the Oregon continental shelf, and the duration, intensity, and frequency of hypoxic events have increased in recent years. In hypoxic regions, iron reduction can liberate dissolved Fe(II) from continental shelf sediments. Fe(II) was measured in the water column across the continental shelf and slope on the Oregon coast during summer 2022 using both a trace metal clean rosette and a high‐resolution benthic gradient sampler. In the summer, Fe(II) concentrations were exceptionally high (40–60 nM) within bottom waters and ubiquitous across the Oregon shelf, reflecting the low oxygen condition (40–70 μM) at that time. The observed inverse correlation between Fe(II) and bottom water oxygen concentrations is in agreement with expectations based on previous work that demonstrates oxygen is a major determinant of benthic Fe fluxes. Rapid attenuation of Fe(II) from the benthic boundary layer (within 1 m of the seafloor) probably reflects efficient cross‐shelf advection. One region, centered around Heceta Bank (~ 44°N) acts a hotspot for Fe release on the Oregon continental shelf, likely due to its semi‐retentive nature and high percent mud content in sediment. The results suggest that hypoxia is an important determinant of the inventory of iron is Oregon shelf waters and thus ultimately controls the importance of continental margin‐derived iron to the interior of the North Pacific Basin. [ABSTRACT FROM AUTHOR]

The acoustic properties of seafloor sediments on continental slopes play a crucial role in underwater acoustic propagation, communication, and detection. To investigate the acoustic characteristics and spatial distribution patterns of sediments on the continental slope, a geoacoustic experiment was conducted in the northwestern South China Sea. The experiment covered two sections: one crossing the shelf and slope in the downslope direction, and the other near the shelf break in the along-slope direction. In situ techniques, sediment sampling, and laboratory measurements were used to acquire data on sediment acoustic properties (such as sound speed and attenuation) and physical properties (including particle composition, density, porosity, and mean grain size). The experimental findings revealed several key points: (1) Acoustic properties of shallow water coarse-grained sediments and deep-sea sediments were higher when measured in the laboratory compared to in situ measurements. (2) Relationships between measured attenuation and physical properties, as well as between sound speed and mean grain size, showed deviations from previous empirical equations. (3) Sediment acoustic and physical properties exhibited significant variations in the downslope direction, while showing gradual variations in the along-slope direction. These variations can be attributed to sedimentary environmental factors such as material sources, hydrodynamic conditions, and water depth. [ABSTRACT FROM AUTHOR]

The Gaoping Submarine Canyon (GPSC) off southwest Taiwan has been extensively studied due to its unique geology, its role in transferring terrestrial material to the deep sea, and its diverse biological communities. However, there is a lack of understanding of carbon cycling across the sediment–water interface in the canyon. This study aims to fill the gap by utilizing the field data collected between 2014 and 2020 and a linear inverse model (LIM) to reconstruct the benthic food web (i.e., carbon flows through different stocks) in the head of GPSC and the upper Gaoping slope (GS). The biotic and abiotic organic carbon (OC) stocks were significantly higher on the slope than in the canyon, except for the bacteria stock. The sediment oxygen utilization was similar between the two habitats, but the magnitude and distribution of the OC flow in the food web were distinctively different. Despite a significant input flux of ∼ 2020 mg C m -2 d -1 in the canyon, 84 % of the carbon flux exited the system, while 12 % was buried. On the slope, 84 % of the OC input (∼ 109 mg C m -2 d -1) was buried, and only 7 % exited the system. Bacteria processes play a major role in the carbon fluxes within the canyon. In contrast, the food web in the upper slope exhibited stronger interactions among metazoans, indicated by higher fluxes between meiofauna and macrofauna compartments. Network indices based on the LIM outputs showed that the canyon head had higher total system throughput (T..) and total system throughflow (TST), indicating greater energy flowing through the system. In contrast, the slope had a significantly higher Finn cycling index (FCI), average mutual information (AMI), and longer OC turnover time, suggesting a relatively more stable ecosystem with higher energy recycling. Due to sampling limitations, the present study only represents the benthic food web during the "dry" period. By integrating the field data into a food web model, this study provides valuable insight into the fates of OC cycling in an active submarine canyon, focusing on the often overlooked benthic communities. Future studies should include "wet" period sampling to reveal the effects of typhoons and monsoon rainfalls on OC cycling. [ABSTRACT FROM AUTHOR]

The storage potential of hydrocarbon reservoirs in the central Gulf of Mexico (GOM) makes future development of CO2 storage projects in those areas promising for secure, large-scale, and long-term storage purposes. Focusing on the producing and depleted hydrocarbon fields in the continental slope of the central GOM, this paper analyzed, assessed, and screened the producing sands and evaluated their CO2 storage potential. A live interactive CO2 storage site screening system was built in the SAS® Viya system with a broad range of screening criteria combined from published studies. This offers the users a real-time assessment of the storage sites and enables them to adjust the filters and visualize the results to determine the most suitable filter range. The CO2 storage resources of the sands were estimated using a volumetric equation and the correlation developed by the National Energy Technology Laboratory (NETL). The results of this study indicate that 1.05 gigatons of CO2 storage resources are available in the developed reservoirs at the upper slope area of the central GOM. The Mississippi Canyon and Green Canyon protraction areas contain the fields with the largest storage resources. [ABSTRACT FROM AUTHOR]

The Ross Sea region Marine Protected Area (RSR MPA) is one of the most productive regions in the Southern Ocean. Mesozooplankton intermediates the primary product to the higher predators, such as penguins and seals, in this ecosystem. In this study, the mesozooplankton community structure and spatial pattern in the RSR MPA in January were investigated by using 505 μm-mesh-size bongo net samples. As a result, 37 mesozooplankton taxa with a total mean abundance of 35.26 ind./m3, ranging from 2.94 to 139.17 ind./m3, were confirmed. Of the 37 taxa, 7 occupied almost 84% of the total abundance, with copepods being the main dominant taxa. As shown by our hierarchical analysis, the mesozooplankton community was divided into four groups, each associated with a specific geographical distribution. Group A was composed of stations around Terra Nova Bay and showed relatively low abundance. Group B included stations around the continental slope region. Group D was composed of the Ross Sea continental shelf stations, while group C consisted of stations geographically located between those of groups B and D. These four groups were influenced by various environmental factors, such as water temperature, salinity, and nutrients. In summary, the mesozooplankton community can be separated according to geographical pattern. This pattern is related to several environmental factors. [ABSTRACT FROM AUTHOR]

The <3% dissimilar Amplicon Sequence Variant (ASV) clusters of the 18S‐V4 barcode were used as species‐proxies for the evaluation of ASV composition and ASV diversity indices characterizing the hitherto poorly investigated meiofaunal communities of the south‐eastern part of the Levantine basin. Accompanied by abundance measurements, the relationships of these characteristics with sedimentary and bottom terrain parameters were interpreted. The construction of community composition profiles, namely ASVs' list and their estimated abundances, was done using our previously established procedure (Harbuzov et al., 2022, Marine Genomics 65, 100980), combining metabarcoding with sample reads normalization by the abundance of hard‐bodied meiofaunal taxa. The study province included the 54–1418 m depth range, across vertical sub‐bottom horizons ranging 0–17 cm. Oxygen, hydrogen sulfide and methane concentrations in the pore water, as well as sediment grain size spectra and sedimentary protein and carbohydrate levels, were measured, followed by an evaluation of their involvement in the shaping of the meiofaunal communities' characteristics. Community composition was generally site‐and‐horizon dependent and its abundance decreased with increasing bottom depth and across sub‐bottom horizons, typical to benthic habitats which are nourished by organic carbon from the euphotic zone. The relatively sharply inclined continental slope bottom located in the northern part of the Israeli coast was an exception. Its meiofaunal community characteristics were speculated to be affected by intensive sediment mixing and lateral transport of food from the shelf, in addition to the effect of the euphotic zone‐originated food sources. [ABSTRACT FROM AUTHOR]

Internal tides are known to be an important source of mixing in the oceans, especially in the bottom boundary layer. The depth of internal-tide generation therefore seems important for benthic life and the formation of cold-water coral mounds, but internal-tide conversion is generally investigated in a depth-integrated sense. Using both idealized and realistic simulations on continental slopes, we found that the depth of internal-tide generation increases with increasing slope steepness and decreases with intensified shallow stratification. The depth of internal-tide generation also shows a typical latitudinal dependency related to Coriolis effects. Using a global database of cold-water corals, we found that, especially in Northern Hemisphere autumn and winter, the global depth pattern of internal-tide generation correlates (rautumn = 0.70, rwinter = 0.65, p < 0.01) with that of cold-water corals: shallowest near the poles and deepest around the Equator, with a decrease in depth around 25° S and N, and shallower north of the Equator than south. We further found that cold-water corals are situated significantly more often on topography that is steeper than the internal-tide beam (i.e. where supercritical reflection of internal tides occurs) than would be expected from a random distribution: in our study, in 66.9 % of all cases, cold-water corals occurred on a topography that is supercritical to the M2 tide whereas globally only 9.4 % of all topography is supercritical. Our findings underline internal-tide generation and the occurrence of supercritical reflection of internal tides as globally important for cold-water coral growth. The energetic dynamics associated with internal-tide generation and the supercritical reflection of internal tides likely increase the food supply towards the reefs in food-limited winter months. With climate change, stratification is expected to increase. Based on our results, this would decrease the depth of internal-tide generation, possibly creating new suitable habitat for cold-water corals shallower on continental slopes. [ABSTRACT FROM AUTHOR]

The article presents observations of near-inertial internal waves (NIWs) in the slope waters of the Black Sea in winter and summer. Rotary spectral analysis of a time series of sea current velocity measurements revealed the prevailing anticyclonic component of the motions near the local inertial frequency f. The clockwise rotation of the velocity vector with depth implies that the NIWs propagate downwards. The amplitude of NIWs usually was 0.1–0.2 m s−1. NIWs were observed in the layer of the permanent pycnocline and the seasonal pycnocline, which attenuate below depths of 160 m and 80 m in winter and summer, respectively. The amplitude of the near-inertial kinetic energy (NIKE) showed a close relationship with vertical stratification. During winter, NIKE exhibited maximum values in the layer of the permanent pycnocline, whereas, in summer, it was primarily observed in the seasonal pycnocline layer. The near-inertial oscillations were generally more energetic in winter. [ABSTRACT FROM AUTHOR]

In the Mesozoic succession of the Anyui–Chukotka fold system (North‐East Russia), five stratigraphic intervals were recognised that have an abundance of gravity flow deposits. These are the Olenekian (Lower Triassic), Upper Carnian, Upper Norian, Oxfordian–Kimmeridgian and Valanginian. The Triassic gravity flow deposits formed on the south‐facing, passive margin of the Chukotka microplate and consist of greywackes and lithic arenites. Palaeocurrent data indicate that the flows were directed towards the south‐east. The Olenekian gravity flow units consist of clast‐rich sandstone deposited on the continental slope, and clast‐poor sandstone deposited at the base of the slope. Upper Carnian mud‐poor sandstones were deposited at the base of the slope and the Norian thin‐bedded turbidites were upper to mid‐slope deposits. The continental margin was affected by tectonism and was uplifted in the latest Triassic–earliest Jurassic, possibly due to the initiation of the southward translation of the Arctic Alaska–Chukotka microplate. Following an Early–Middle Jurassic uplift of the area, sedimentation resumed in the Late Jurassic and earliest Cretaceous. Several syn‐orogenic depressions (Rauchua, Pegtymel, Pevek, Myrgovaam and Kytepveem) developed on the south‐western margin of the Chukotka microplate, and deposition in these basins included gravity flow deposits at various times. In both the Oxfordian–Kimmeridgian and Valanginian successions, gravity flow deposits included arkosic and subarkosic sandstones with a northern source area of granitoid complexes and deformed Triassic strata. The intervening Tithonian–Berriasian gravity flow deposits consisted mainly of thin‐bedded turbidites. These sediments had a southern source, which included a volcanic arc that had accreted to the southern margin of the Chukotka microplate. [ABSTRACT FROM AUTHOR]

Marine plastic pollution is currently one of the most serious environmental threats. In this study, based on scenario calculations for a five-year period, we analyzed the possible spread of microplastics carried by Siberian rivers to the Kara Sea shelf. The Lagrangian particle model used daily data from 3D numerical modeling to simulate microplastic transport by ocean currents and sea ice drift. The results of a series of scenario calculations show how the distribution of particles and their subsequent deposition depend on their type (density), size, processes of freezing into the ice, and biofouling (accumulation of microorganisms). The crucial influence of the effects of microplastic embedding in sea ice and particle biofouling on the trajectories of floating particles and their deposition on the seafloor is highlighted. The transport of light particles of microplastics from Siberian rivers by ice can contribute to the pollution of the Barents Sea, in addition to their more active outflow through the Fram Strait. Biofouling is a driver of microplastic deposition on the shelf bottom or transport along the continental slope in a cyclonic direction following the trajectory of the Atlantic waters. [ABSTRACT FROM AUTHOR]

Scientific bottom-trawl surveys are ecological observation programs conducted along continental shelves and slopes of seas and oceans that sample marine communities associated with the seafloor. These surveys report taxa occurrence, abundance and/or weight in space and time, and contribute to fisheries management as well as population and biodiversity research. Bottom-trawl surveys are conducted all over the world and represent a unique opportunity to understand ocean biogeography, macroecology, and global change. However, combining these data together for cross-ecosystem analyses remains challenging. Here, we present an integrated dataset of 29 publicly available bottom-trawl surveys conducted in national waters of 18 countries that are standardized and pre-processed, covering a total of 2,170 sampled fish taxa and 216,548 hauls collected from 1963 to 2021. We describe the processing steps to create the dataset, flags, and standardization methods that we developed to assist users in conducting spatio-temporal analyses with stable regional survey footprints. The aim of this dataset is to support research, marine conservation, and management in the context of global change. [ABSTRACT FROM AUTHOR]

The structural styles and magnitudes of Alpine tectonic inversion are reviewed for the Atlantic margin of southwestern (SW) Iberia, a region known for its historical earthquakes, tsunamis and associated geohazards. Reprocessed, high-quality 2D seismic data provide new images of tectonic faults, which were mapped to a depth exceeding 10 km for the first time. A total of 26 of these faults comprise syn-rift structures accommodating vertical uplift and horizontal advection (shortening) during Alpine tectonics. At the regional scale, tectonic reactivation has been marked by (a) the exhumation of parts of the present-day continental shelf, (b) local folding and thrusting of strata at the foot of the continental slope, and (c) oversteepening of syn- and post-rift sequences near reactivated faults (e.g. "passive uplift"). This work proves, for the first time, that geometric coherence dominated the growth and linkage of the 26 offshore faults mapped in SW Iberia; therefore, they are prone to reactivate as a kinematically coherent fault network. They form 100–250 km long structures, the longest of which may generate earthquakes with a momentum magnitude (Mw) of 8.0. Tectonic inversion started in the Late Cretaceous, and its magnitude is greater close to where magmatic intrusions are identified. In contrast to previous models, this work postulates that regions in which Late Mesozoic magmatism was more intense comprise thickened, harder crust and form lateral buttresses to northwest–southeast compression. It shows these structural buttresses to have promoted the development of early stage fold-and-thrust belts – typical of convergent margins – in two distinct sectors. [ABSTRACT FROM AUTHOR]

The identification of important habitat and the behavior(s) associated with it is critical to conservation and place‐based management decisions. Behavior also links life‐history requirements and habitat use, which are key to understanding why animals use certain habitats. Animal population studies often use tracking data to quantify space use and habitat selection, but they typically either ignore movement behavior (e.g., foraging, migrating, nesting) or adopt a two‐stage approach that can induce bias and fail to propagate uncertainty. We develop a habitat‐driven Langevin diffusion for animals that exhibit distinct movement behavior states, thereby providing a novel single‐stage statistical method for inferring behavior‐specific habitat selection and utilization distributions in continuous time. Practitioners can customize, fit, assess, and simulate our integrated model using the provided R package. Simulation experiments demonstrated that the model worked well under a range of sampling scenarios as long as observations were of sufficient temporal resolution. Our simulations also demonstrated the importance of accounting for different behaviors and the misleading inferences that can result when these are ignored. We provide case studies using plains zebra (Equus quagga) and Steller sea lion (Eumetopias jubatus) telemetry data. In the zebra example, our model identified distinct "encamped" and "exploratory" states, where the encamped state was characterized by strong selection for grassland and avoidance of other vegetation types, which may represent selection for foraging resources. In the sea lion example, our model identified distinct movement behavior modes typically associated with this marine central‐place forager and, unlike previous analyses, found foraging‐type movements to be associated with steeper offshore slopes characteristic of the continental shelf, submarine canyons, and seamounts that are believed to enhance prey concentrations. This is the first single‐stage approach for inferring behavior‐specific habitat selection and utilization distributions from tracking data that can be readily implemented with user‐friendly software. As certain behaviors are often more relevant to specific conservation or management objectives, practitioners can use our model to help inform the identification and prioritization of important habitats. Moreover, by linking individual‐level movement behaviors to population‐level spatial processes, the multistate Langevin diffusion can advance inferences at the intersection of population, movement, and landscape ecology. [ABSTRACT FROM AUTHOR]

We investigate the interaction between an anticyclonic eddy (AE) and semidiurnal internal tide (SIT) on the continental slope of the northeastern South China Sea (SCS), using a high spatiotemporal resolution numerical model. Two key findings are as follows: first, the AE promotes energy conversion from low-mode to higher-mode SIT. Additionally, production terms indicate that energy is also transferred from the SIT field to the eddy field at an average rate of 3.0 mW m -2 (accounting for 7 % of the incoming energy flux of SIT when integrated over the eddy diameter). Second, the AE can modify the spatial distribution of tidal-induced dissipation by refracting, scattering, and reflecting low-mode SIT. The phase and group velocities of the SIT are significantly influenced by the eddy field, resulting in a northward or southward shift in the internal tidal rays. These findings deepen our understanding of the complex interactions between AE and SIT, as well as their impacts on energy conversion, wave propagation, and coastal processes. [ABSTRACT FROM AUTHOR]

The characteristics and mechanism of the southern South China Sea (SCS) Western Boundary Current (WBC) summer-winter transition have been investigated. The transition typically starts in early October and lasts for about two weeks. Above the thermoclines (~100 m), the transition is simultaneous with depth, while below the thermoclines the transition in deeper layer significant lags that in the shallow layers. The geostrophic balance dominates the transition of WBC. Above the thermocline, the transition is determined by the barotropic pressure gradient component. Below the thermocline, the transition is determined by the competition between the barotropic and baroclinic pressures components. When the southern SCS WBC transition above the thermocline starts, the barotropic and baroclinic pressures components offset each other below the thermocline, resulting in the lag of the geostrophic balance. With the depth increases, more time is needed for the barotropic pressures component to enhance enough to dominate a geostrophic balance, which induces the transition lag with depth. Changes in the barotropic pressure gradient component are mainly due to the variations in SCS basin scale wind stress curl, while changes in the baroclinic pressure gradient component below the thermocline are associated with the warming of the deeper water column caused by the downwelling near the continental slope and the disappearing of upwelling off Vietnam. [ABSTRACT FROM AUTHOR]

The results of gas geochemical and lithogeochemical studies of bottom sediments in the Tatar Strait trough (Sea of Japan) based on cruise data from the R/V Akademik M.A. Lavrentyev (LV-81 and LV-85) are presented. Anomalies of hydrocarbon gases (HCGs) and chemical elements in the surface bottom sediments were determined. It has been established that sediments with anomalous methane contents are significantly enriched in Mn, Sc, V, Co, Ni, Cu, As, Se, Mo, Cd, Sb, Te, Tl, and U, the coefficients of the concentration (Kc) of which are 1.3–5.9 times higher than similar values at other stations. The data obtained allow us to assume the presence of gas sources of hydrocarbon migration; the continental slope and deep-water area of the Tatar trough are promising for setting up detailed work on the assessment of the oil and gas potential and the gas hydrate content. [ABSTRACT FROM AUTHOR]

Compressional velocity (Vp) and bulk density (ρb) logs are essential for characterizing gas hydrates and near-seafloor sediments; however, it is sometimes difficult to acquire these logs due to poor borehole conditions, safety concerns, or cost-related issues. We present a machine learning approach to predict either compressional Vp or ρb logs with high accuracy and low error in near-seafloor sediments within water-saturated intervals, in intervals where hydrate fills fractures, and intervals where hydrate occupies the primary pore space. We use scientific-quality logging-while-drilling well logs, gamma ray, ρb, Vp, and resistivity to train the machine learning model to predict Vp or ρb logs. Of the six machine learning algorithms tested (multilinear regression, polynomial regression, polynomial regression with ridge regularization, K nearest neighbors, random forest, and multilayer perceptron), we find that the random forest and K nearest neighbors algorithms are best suited to predicting Vp and ρb logs based on coefficients of determination (R2) greater than 70% and mean absolute percentage errors less than 4%. Given the high accuracy and low error results for Vp and ρb prediction in both hydrate and water-saturated sediments, we argue that our model can be applied in most LWD wells to predict Vp or ρb logs in near-seafloor siliciclastic sediments on continental slopes irrespective of the presence or absence of gas hydrate. [ABSTRACT FROM AUTHOR]

Energetic tidal currents in the Arctic play an important role in local mixing processes, but they are primarily confined to the shelves and continental slopes due to topographic trapping north of their critical latitude. Recent studies employing idealized models have suggested that the emergence of higher harmonic tidal waves along these slopes could serve as a conduit for tidal energy transmission into the Arctic Basin. Here we provide observational support from an analysis of yearlong observations from three densely-instrumented oceanographic moorings spanning 30 km across the continental slope north of Svalbard (∼ 81.3 ∘ N). Full-depth current records show strong barotropic diurnal tidal currents, dominated by the K 1 constituent. These sub-inertial currents vary sub-seasonally and are strongest at the 700-m isobath due to the topographic trapping. Coinciding with the diurnal tide peak in summer 2019, we observe strong baroclinic semidiurnal currents exceeding 10 cm s - 1 between 500 m and 1000 m depth about 10 km further offshore at the outer mooring. In this semidiurnal band, we identify super-inertial K 2 waves, and present evidence that their frequency, timing, polarization, propagation direction and depths are consistent with the generation as higher harmonics of the topographically trapped K 1 tide at the continental slope. [ABSTRACT FROM AUTHOR]

In natural systems, animal‐mediated nutrient transport can be a major driver of primary productivity, but the role of marine megafauna such as cetaceans in mediating the transfer and recycling of nutrients has been overlooked. Here, we developed a spatially resolved, stochastic, nutrient‐transport model for cetaceans in the oceanic Gulf of Mexico using species−specific foraging depths, distributions, and diets. An estimated 6.4 × 108 mmol N d−1, or 0.06 mt N yr−1 ind−1, is transported to the surface from depths below 100 m by the 19 cetacean species that occur in the oceanic Gulf of Mexico; 75% of this transport occurs seaward of the continental slope, but the per area transported nitrogen is greater on the continental slope (200–1000 m) than in the ocean basin. Benthos to surface transport comprised 6.0 × 107 mmol N d−1 and was much more common on the continental slope than the open basin. Compared to an existing physical‐biogeochemical model, the transported nutrients add 8% N d−1 to the estimated ammonium concentration above the nutricline and could add 16% N d−1 to the surface ammonium concentration if expelled nutrients remain at the surface. Through feeding on diel vertical migrants, cetaceans retain an additional 2.7 × 107 mmol N d−1 in the surface waters that would otherwise return to depth via downward diel vertical migration. Cetaceans contribute to nutrient movements and recycling in the oceanic Gulf of Mexico, and may provide one of the few allochthonous sources of nutrients for primary producers in oligotrophic ecosystems. [ABSTRACT FROM AUTHOR]

High-resolution seismic analysis and bathymetry data, used in the Offshore Sinú Fold Belt (OSFB), have revealed seabed and sub-surface anomalies, which were probably caused by the presence of shallow gas within the sedimentary records. Shallow gas is widely detected by the frequent presence of anomalous acoustic reflections including acoustic blanking, enhanced reflections, acoustic plumes, pockmarks, and dome structures. More than 30 anomalies that occur within a subsurface depth of ~65 m were acoustically detected within an area of 1000 km2 on the continental shelf and upper continental slope, in water depths ranging from −20 to −1300 m. Moreover, a map with the spatial distribution of the gas occurrences is shown. A close relationship between the locally elevated seabed (dome structures), pockmarks, and acoustic blanking was found. Most of the active pockmarks may be closely related to the submarine path of the Uramita Fault, indicating that the gas occurrences are controlled by active faulting. The shallow gas occurrence was confirmed by the generation of authigenic carbonate and the occurrence of chemosymbiotic biological communities sampled in the area. Although there is an admixture of biogenic gas, it is believed that many of the features observed relate to thermogenic gas. The identification of these anomalies represents a useful basis for an assessment of marine geohazards and can serve as a hydrocarbon exploration tool. [ABSTRACT FROM AUTHOR]

Against the background of wind-forcing change along with Arctic sea ice retreat, the mesoscale processes undergoing distinct variation in the Beaufort Gyre (BG) region are increasingly important to oceanic transport and energy cascades, and these changes subsequently put oceanic stratification into a new state. Here, the varying number and strength of eddies in the central Canada Basin (CB) and Chukchi–Beaufort continental slope are obtained based on mooring observations (2003–2018), altimetry measurements (1993–2019), and reanalysis data (1980–2020). In this paper, the variability in the BG halocline, representing the adjustment of stratification in the upper layer, is shown in order to analyse how variability occurs under changing mesoscale processes. We find that over almost the last 2 decades the halocline depth has deepened by ∼ 40 m in the south of the central gyre, while that in the north has deepened by ∼ 70 m according to multiple datasets. Surrounding the central gyre, the asymmetry of the halocline, with much steeper and deeper isopycnals over the southern continental slope, reduced after 2014. In the meantime, eddy activities in the upper layer from the southern margin of the BG to the abyssal plain have been enhanced. Moreover, the convergence of the eddy lateral flux has increased as the halocline structures on either side, which is at least 120 km from the central gyre, have reached a nearly identical and stable regime. It has been clarified that long-term dynamic eddy modulation through eddy fluxes, facilitating the freshwater redistribution, affects the meridional asymmetry of the BG halocline. Our results provide a better understanding of the eddy modulation processes and their influence on the halocline structure. [ABSTRACT FROM AUTHOR]

The transfer of nutrients and energy from carcasses to scavengers is an important ecosystem function. In marine ecosystems, mammal carcasses can represent a spatiotemporally restricted but substantial pulse in resource availability, as they are typically only briefly available to scavengers on the surface. Little is understood about how these scavengers respond to such pulses, or how inter-scavenger interactions may influence their behaviour. We describe scavenging interactions of procellariiform seabirds at a fresh and floating New Zealand Fur Seal Arctocephalus forsteri carcass, recently killed by a White Shark Carcharodon carcharias, over the continental slope of southeastern Australia. We highlight potential exclusive and facilitative interactions between the shark and various seabirds, which may play an important role in energy-transfer dynamics in surface pelagic environments. We also provide apparently novel descriptions of scavenging at a marine mammal carcass for six of the seven seabird species that attended the carcass. Further study of sea-surface scavenger behaviour, interactions, and ecology will provide valuable insights into energy-transfer dynamics in pelagic ecosystems. [ABSTRACT FROM AUTHOR]

We have analyzed the MZ6 onshore‐offshore wide‐angle seismic profile of the MOZ3‐5 survey to investigate the crustal structure of the South Mozambique passive margin. The NNW‐SSE, 625 km‐long profile runs across the Mozambique coastal plain (MCP), the Continental Shelf and Slope, the Almirante Leite Ridge (ALR), the North Natal Valley (NNV), the Ariel Graben and the Dana Plateau of the Mozambique Ridge. Forward modeling through combined interpretation of the multichannel seismic, the main reflected and refracted phases of the wide‐angle, drill hole data and bathymetric data reveal: (a) a sedimentary cover poorly compacted up to 3 km‐thick, intruded by magmatic dykes that reach the seafloor at the ALR forming 0.5 to 5 km‐wide corrugated mounts, (b) between 2 and 7 km, thick magmatic or volcano‐clastic deposits are observed both at the MCP and NNV, forming a 40 km‐wide terrace at the center of MZ6 and southward‐dipping reflectors in the southern part interpreted as the Pre‐Neocomian Formation contemporary of the Karroo and/or Bombeni‐Movene magmatic events reached in several wells, (c) onshore, the 3‐layered crust reaches 39 km thickness, gradually thinning to ∼27 km at the southern end of MZ6. In the deepest layer, velocities exceed 7.15 km/s, reaching at its base 7.55 km/s at the vertical of the ALR. (d) the seismic Moho is marked by a strong reflection on the wide‐angle data. These results suggests that the basement is composed of slightly thinned and altered continental crust, most likely intruded by several phases of intense magmatism. Plain Language Summary: About 200 Ma ago, the mega‐continent Pangaea broke up. The dispersion of the pieces, linked to the closure and disappearance of the Thetys paleo‐ocean, gave the birth of the Atlantic and Indian Oceans. In detail, the initial position of each piece of this jigsaw is of great importance as it has an impact on our understanding of the genesis of the continental passive margins, the role of tectonic inheritance, the pre‐rift and post‐rift evolution of the topography dynamic (vertical movement) and of the geodynamic of the plates (horizontal movement). Nevertheless, in the Western Indian Ocean, the initial pre‐beak‐up position of Antarctica plate respect to Africa plate is still under debate, mainly due to the lack of deep geophysical data. In 2016, an academic‐industrial collaboration succeeded in acquiring deep information along seven seismic profiles crossing the North Natal Valley (NNV) off the coast of Mozambique. The results falsify the presence of an oceanic crust in that area and thus most of the plate reconstruction models. The NNV presents a thick continental crust intrudedded by several phases of intense magmatism, with at its top, a volcano‐clastic pre‐Neocomian Fm contemporary of the crustal thinning and subsequent spreading between Africa and Patagonia plates. Key Points: The North Natal Valley (NNV) presents a ∼30 km‐thick continental crust, in contrary to what is proposed in most geodynamic modelsVelocity variations in the middle‐lower part of this crust probably represent mantle intrusions during several phases of intense magmatismOn the top of the basement, there is a volcano‐clastic pre‐Neocomian Fm, probably contemporary of the movement of the Patagonia plate [ABSTRACT FROM AUTHOR]

The Gaoping Submarine Canyon (GPSC) off Southwest Taiwan has been extensively studied due to its unique geology, the role of transferring terrestrial material to the deep sea, and diverse biological communities. However, there is a lack of understanding of carbon cycling across the sediment--water interface in the canyon. This study aims to fill the gap by utilizing the field data collected between 2014 and 2020 and the Linear Inverse Model (LIM) to reconstruct the benthic food web (i.e., carbon flows through different stocks) in the head of GPSC and the upper Gaoping slope (GS). The biotic and abiotic organic carbon (OC) stocks were significantly higher on the slope than in the canyon, except for the bacteria stock. The sediment oxygen utilization was similar between the two habitats, but the magnitude and distribution of the OC flow in the food web were distinctively different. Despite a significant input flux of ~1400 mg C m-2 d-1 in the canyon, 85% of the carbon flux exited the system, while 14% was buried. On the slope, 75% of the OC input (~105 mg C m-2 d-1) was buried, and only 11% exited the system. Bacteria processes play a major role in the carbon fluxes within the canyon. In contrast, the food web in the upper slope exhibited stronger interactions among metazoans, indicated by higher fluxes between meiofauna and macrofauna compartments. Network indices based on the LIM outputs showed that the canyon head had higher total system throughput (T..) and total system through flow (TST), indicating greater energy flowing through the system. In contrast, the slope had a significantly higher Finn cycling Index (FCI), average mutual information (AMI), and longer OC turnover time, suggesting a relatively more stable ecosystem with higher energy recycling. Due to sampling limitations, the present study only represents the benthic food web during the "dry" season. By integrating the field data into a food web model, this study provides valuable insight into the fates of OC cycling in an active submarine canyon, focusing on the often overlooked benthic communities. Future studies should include "wet" season sampling to reveal the effects of typhoons and monsoon rainfalls on OC cycling. [ABSTRACT FROM AUTHOR]

Liang, Z.; Ji, D.; Zhang, X.; Lingyun, W.; Zhang, T.; Li, S.; Yong, J.; Luo, J.; Liu, Y., and Zeng, J., 2023. Carboniferous oceanic basin sediment-gravity flows in the margin of the Junggar Basin, NW China: Characterisation and implications for hydrocarbon potential and evolution pacing. Journal of Coastal Research, 39(5), 890–906. Charlotte (North Carolina), ISSN 0749-0208. Several Carboniferous deep-marine-sandstone reservoirs have recently been discovered in the Junggar Basin, NW China. These reservoir sandstones were deposited by sediment-gravity flows that occurred on the continental slope of the Junggar Basin, and they have high hydrocarbon exploration potential. In this study, careful observations and petrological and geochemical analyses of samples from outcrop sections of Carboniferous rocks from the Junggar Basin were conducted to establish the deep-marine sedimentary characteristics, depositional environments, and mechanism of these gravity-flow deposits, as well as a sedimentary model for their occurrence. The deep-marine, gravity-flow deposit types include those of turbidity currents, debris flows, and slumps. The debris-flow deposits can be divided into pebbly debris-flow deposits and sandy debris-flow deposits. Results allow the relationship between the type and nature of gravity flows and ocean basin evolution to be established. During the early Carboniferous, the ocean basin had sufficient space to accommodate incoming sediment, and the sediment transport distance was long. The gravity-flow sediments of this period are dominated by sandy debris-flow deposits and turbidity-flow deposits characterised by thin individual layers but thick accumulations of multiple deposits. With continuous narrowing of the oceanic basin during the late Carboniferous, the basin had a smaller accommodation space. The main types of gravity-flow deposition during this period were pebbly and sandy debris flows, with rare thin turbidity-flow deposits. These deposits were coarser grained than their early Carboniferous equivalents, and their cumulative thicknesses were smaller. The results of the study provide insights into the prediction of deep-marine reservoir sandstones and the distribution of hydrocarbons in the Junggar Basin. [ABSTRACT FROM AUTHOR]

The Antarctic Slope Current is guided by the topographic gradient of the Antarctic continental slope and creates a dynamical barrier between the continental shelf and the open ocean. The current's vertical structure varies around the continent affecting cross‐slope water mass exchange with consequences for Antarctic mass loss, ventilation of the deep ocean, and carbon uptake. The Antarctic Slope Current is surface‐intensified in many regions but bottom‐intensified in regions of dense overflows. This study investigates the role of dense overflows in modifying the dynamics of the bottom‐intensified flow using a 0.1° global ocean‐sea ice model. The occurrence of bottom‐intensification is tightly linked with dense overflows and bottom speeds correlate with dense overflows on interannual time scales. A lack of vertical connectivity between the bottom and surface flow, however, suggests that the along‐slope bottom water flows are coincidentally co‐located with the Antarctic Slope Current, rather than dynamically a part of the current. Plain Language Summary: The Antarctic Slope Current is a narrow ocean current that travels around Antarctica following the continental slope. It separates the shallow and cold continental shelf from much warmer waters in the open ocean. Intrusions of the relatively warm water across the continental slope impacts melting of Antarctic ice shelves and global sea level rise. Understanding what controls the strength and variability of the Antarctic Slope Current is therefore important. The Antarctic Slope Current usually has the largest velocities near the surface, but there are regions where there is also a strong bottom flow. We use a coupled ocean‐sea ice model and show that the bottom flow is controlled by the export of very dense shelf water that flows down the continental slope in a few locations around the continent. However, the bottom and surface flow does not vary together on interannual time scales which tells us that the two components of the Antarctic Slope Current are largely independent. The result is important as the formation of dense shelf water is expected to reduce in the future which will impact the deep flow, but not the surface component. Key Points: Simulations reveal a close spatial relationship between the bottom‐intensified Antarctic Slope Current and Dense Shelf Water exportInterannual variability of Dense Shelf Water is reflected in the bottom speed of the bottom‐intensified Antarctic Slope CurrentThe surface component varies independently from the bottom‐intensified flow implying two distinct, co‐located currents [ABSTRACT FROM AUTHOR]

Proton-pump rhodopsin (PPR) in marine microbes can convert solar energy to bioavailable chemical energy. Whereas bacterial PPR has been extensively studied, counterparts in microeukaryotes are less explored, and the relative importance of the two groups is poorly understood. Here, we sequenced whole-assemblage metatranscriptomes and investigated the diversity and expression dynamics of PPR in microbial eukaryotes and prokaryotes at a continental shelf and a slope site in the northern South China Sea. Data showed the whole PPRs transcript pool was dominated by Proteorhodopsins and Xanthorhodopsins, followed by Bacteriorhodopsin-like proteins, dominantly contributed by prokaryotes both in the number and expression levels of PPR unigenes, although at the continental slope station, microeukaryotes and prokaryotes contributed similarly in transcript abundance. Furthermore, eukaryotic PPRs are mainly contributed by dinoflagellates and showed significant correlation with nutrient concentrations. Green light-absorbing PPRs were mainly distributed in >3 μm organisms (including microeukaryotes and their associated bacteria), especially at surface layer at the shelf station, whereas blue light-absorbing PPRs dominated the <3 μm (mainly bacterial) communities at both study sites, especially at deeper layers at the slope station. Our study portrays a comparative PPR genotype and expression landscape for prokaryotes and eukaryotes in a subtropical marginal sea, suggesting PPR's role in niche differentiation and adaptation among marine microbes. [ABSTRACT FROM AUTHOR]

Lumbrineriopsis dulcis sp. nov. is morphologically described from the continental shelf and slope of Espírito Santo and the Campos Basin of Rio de Janeiro state, southeastern Brazil, at depths between 14 and 400 m. Lumbrineriopsis mucronata is the only species of the genus recorded until now in Brazil. The new species differs from other congeneric species in its jaw-apparatus morphology with unfused mandibles and a fixed number of simple limbate chaetae and simple, bidentate, hooded hooks in each parapodium. This paper aims to fill the gap in knowledge on the family Lumbrineridae, which has not been studied in Brazil for the last 25 years and provides the first record of the genus from Espírito Santo and Rio de Janeiro states. This record is significant given the damage to the marine ecosystem of the Espírito Santo region due to the 2015 rupture of the Samarco mining company dam, the largest environmental disaster in Brazil's history. In addition, this region has important environmental conservation units such as Costa das Algas Environmental Protection Area, Santa Cruz Wildlife Refuge, and Comboios Biological Reserve. All these preserved areas are of paramount importance for the protection of marine biological diversity. [ABSTRACT FROM AUTHOR]

Continental slopes can play a significant contribution to marine productivity and carbon cycling. These regions can harbour distinct geological features, such as salt diapirs and pockmarks, in which their depressions may serve as natural sediment traps where different compounds can accumulate. We investigated the prokaryotic communities in surface (0–2 cm) and subsurface (18–20 or 22–24 cm) sediments from a salt diapir and pockmark field in Santos Basin, Southwest Atlantic Ocean. Metabarcoding of 16 samples revealed that surface sediments were dominated by the archaeal class Nitrososphaeria, while the bacterial class Dehalococcoidia was the most prevalent in subsurface samples. Sediment strata were found to be a significant factor explaining 27% of the variability in community composition. However, no significant difference was observed among geomorphological features. We also performed a metagenomic analysis of three surface samples and analysed the highest quality metagenome-assembled genome retrieved, which belonged to the family CSP1–5, phylum Methylomirabilota. This non-methanotrophic methylotroph contains genes encoding for methanol oxidation and Calvin Cycle pathways, along with diverse functions that may contribute to its adaptation to deep-sea habitats and to oscillating environmental conditions. By integrating metabarcoding and metagenomic approaches, we reported that CSP1–5 is prevalent in the sediment samples from Santos Basin slope, indicating the potential importance of methanol metabolism in this region. Finally, using a phylogenetic approach integrating 16S rRNA sequences assigned to Methylomirabilota in this study with those from a public database, we argued that CSP1–5 public sequences might be misclassified as Methylomirabilaceae (the methanotrophic clade) and, therefore, the role of these organisms and the methanol cycling could also be neglected in other environments. [ABSTRACT FROM AUTHOR]

The sedimentary dynamics and geological evolution of the Naples canyons during the Late Quaternary have been studied based on sedimentological and seismo-stratigraphic data. Several factors, including the sedimentary environments, tectonic setting, and volcanic eruptions, have controlled the geological evolution of the coastal and marine areas of the Bay of Naples. The main data and methods include the sedimentological data analysis, the seismo-stratigraphic techniques applied in the geological interpretation of seismic profiles, and the integrated analysis of core data that were previously published. The formation of the Dohrn canyon is controlled by fluvial processes, active in correspondence with the palaeo-Schiazzano River system and by the main eruptive events involving the submarine portion of Naples Bay, including the Campanian Ignimbrite (CI; 39 ky B.P.) and the Neapolitan Yellow Tuff (NYT; 15 ky B.P.). The formation of the Magnaghi canyon is controlled by erosional processes on the continental slope of Procida Island, which was active during the last eruptive phases of the island (Solchiaro Formation; 18 ky B.P.), triggering high rates of volcaniclastic supply. [ABSTRACT FROM AUTHOR]

This paper presents a significant advancement in the understanding of tsunamigenic landslide hazard across the length of the Makassar Strait in Indonesia. We use statistical emulation across the length of the continental slope to conduct a probabilistic assessment of tsunami hazard on a regional scale, across 14 virtual coastal gauges. Focusing on the potential maximum wave amplitudes (distance between the wave crest and the still‐water level) from possible tsunamigenic landslide events, we generate predictions from Gaussian Process emulators fitted to input‐outputs from 50 training scenarios. We show that the most probable maximum wave amplitudes in the majority of gauges are between 1 and 5 m, with the maximum predicted amplitudes reaching values of up to 10 m on the eastern coast, and up to 50 m on the western coast. We also explore the potential use of Gaussian multivariate copulas to sample emulator prediction input values to create a more realistic distribution of volumes along the continental slope. The novel use of statistical emulation across a whole slope enables the probabilistic assessment of tsunami hazard due to landslides on a regional scale. This area is of key interest to Indonesia since the new capital will be established in the East Kalimantan region on the western side of the Makassar Strait. Plain Language Summary: This work is the first to use statistical models to conduct a landslide‐generated tsunami hazard assessment for the whole of the Makassar Strait in Indonesia. From 50 simulated landslide‐tsunami scenarios, we fit statistical models (known as emulators) to then predict the likelihood and maximum wave height of potential tsunami waves in 14 different locations along the Makassar continental slope. These predictions show that the most likely wave heights were between 1 and 5 m, with the highest predicted waves reaching up to 10 m on the eastern coast and up to 50 m on the western coast. The results of this study are particularly important because Indonesia has announced the relocation of its new capital city to the western side of the Makassar Strait, within the study area. Key Points: This is the first use of emulation for tsunamigenic landslide hazard assessment worldwide integrating both uncertain location and sizeThis is the first tsunamigenic landslide hazard assessment for the whole Makassar Strait regionProbable tsunami wave amplitudes reach up to 50 m on the West coast and around 14 m where the Indonesian capital will be relocated [ABSTRACT FROM AUTHOR]

The paper analyzes quasiperiodic upwellings and downwellings on the shelf and upper part of continental slope of the northeastern Black Sea. It is shown that these processes are related to changes in intensity and direction of alongshore current and the following geostrophic adjustment of the density field. The source of such changes is the meandering of the Black Sea Rim Current (RC). It leads to a quasiperiodic change in direction of the alongshore current, from northwestern (cyclonic RC meander) to southeastern (anticyclonic RC meander, or eddy). These cycles, or phases, have an average duration of about 10 days. During the northwestern phase, the permanent Black Sea pycnohalocline (hereafter pycnocline) and seasonal thermocline descend, their thickness increases, and so does the thickness of the upper mixed layer (UML). During the southeastern phase, both the pycnocline and seasonal thermocline ascend and become thinner, along with the UML, which also becomes thinner. In both phases, isopycnals in the pycnocline and isotherms in the thermocline demonstrate quasi-in-phase vertical oscillations, which have a good correlation with the speed and direction of the alongshore current. These correlations allow estimation of the magnitude of upwellings and downwellings in the shelf–slope area of the northeastern Black Sea using data series of current velocity profiles. [ABSTRACT FROM AUTHOR]

The structure and productivity of planktonic microbial communities in the ecosystems of the Siberian Arctic seas are significantly dependent on freshwater input. During the study, we determined the spatial distribution of the abundance, biomass, and production of heterotrophic bacterioplankton in the Western Laptev Sea on the transect from the Khatanga River estuary to the continental slope and assessed the impact of river freshwater discharge. The influence of fresh water on bacterioplankton was restricted mainly to Khatanga Bay (KHAB) and the transitional zone (TZ) and was poorly recognized in the Western shelf (WS) and continental slope (CS) areas. The total bacterial abundance decreased from KHAB to the CS. Particle-attached bacteria constituted on average 63.0% of the total abundance of bacterioplankton in KHAB and 1.0% at the CS. Average bacterial production in the water column was highest in KHAB (10.3 mg C m−3 d−1), decreasing towards the CS (0.7 mg C m−3 d−1). In KHAB and TZ, bacteria were the main component of the planktonic community (44−55%). These results show that at the end of the growing season, bacterial processes prevailed over autotrophic ones and contributed largely to the total biological carbon flux in the coastal ecosystem of the Western Laptev Sea. [ABSTRACT FROM AUTHOR]

Benthic samples collected from depths ranging between 686 and 2410 m along the Brazilian continental upper slope from Rio de Janeiro State to Santa Catarina State (23°S to 27°S) yielded a wealth of tanaidacean material, including two new species of Stenotanais. This is the first described species of the family Akanthophoreidae from Brazilian waters. Stenotanais leonardoi sp. nov. has a combination of unique characters including the uropod basal article longer than the pleotelson and the exopod somewhat wider than the endopod, longer than the endopod article-1 (0.7 times endopod length) and supporting two flat and wide terminal setae. Stenotanais uropedon sp. nov. is recognisable by its oar-shaped uropod endopod, with article-2 large, broad and flattened and the short exopod, only 0.3 times the endopod length. An identification key to the species of Stenotanais is given. These two species bring the total number of described akanthophoreids to 56 species and that of all tanaidaceans in Brazilian waters to 66 species. [ABSTRACT FROM AUTHOR]

Core samples from Ilaro BH-7 (51-202m) in the eastern Dahomey basin were subjected to standard foraminiferal biostratigraphic analysis to determine their foraminiferal assemblages, diversity, age and paleoenvironments. The benthic foraminiferal species were subjected to stable isotope analyses to identify possible records of the Paleocene-Eocene Thermal Maximum. The sediments are essentially silicified limestones, sandstones and shales/mudstones, with thin beds of siltstones. Identified foraminiferal assemblages consists of 16 planktic, 12 benthic and 2 agglutinated species belonging to two planktic foraminiferal zones, P4-P7 and P8, defined by Acarinina pentacamerata and the Pseudohastigerina micra, respectively. The planktic/benthic foraminiferal ratios varied between 22 and 84%. The Shannon-Wiener and Fisher Alpha species richness and diversity averages are 1.99 and 1.13, respectively. δ13C in benthic foraminifera showed negative to strong negative chemostratigraphic curve from 0.59 ‰ to -15.66‰, while δ18O showed slightly strong negative shift from -1.81‰ to - 6.76‰. Recovered species exhibited moderate diversity and were almost entirely calcareous assemblages, indicating restricted environmental conditions in the borehole. The sediments were assigned ages of 50.2Ma, 50.5Ma and 57.7Ma corresponding to Late Paleocene to Early Eocene. The depositional environment ranged from inner shelf to upper continental slope. The oxygen isotope revealed a synchronous negative short-term excursion with cyclic fluctuation owing to the changing water temperature in the environment. The temperature may not play significant role in the extinction of the benthic foraminifera because of their adaptation to δ18O depleted environment. However, strong negative shift of carbon isotope revealed Thermal Maximum event in the studied interval. [ABSTRACT FROM AUTHOR]

Squaliform sharks are relatively vulnerable bycatch in many deepwater fisheries. The diets of two deep-water sharks, Deania calcea and Deania profundorum, on the continental slope and continental shelf (200-1100 m) of the Moroccan coasts (North-East Atlantic) were subjected to an examination of the stomach content using monthly samples collected between February 2018 and March 2021. For investigation, 683 Deania calcea individuals were collected, ranging in size from 55 to 116cm, with 423 females and 267 males. While, 161 Deania profundorum individuals were sampled, with 117 females and 44 males ranging in size from 49 to 100cm. It was observed that, the diet of both Deania calcea and Deania profundorum consisted of four essential prey groups; cephalopods, bony fish, crustaceans and annelids. The main prey species of the two deep-sea sharks studied were the bony fish, cephalopods and crustaceans. This study would provide comprehensive information for the conservation of the species under study and managing a good exploitation. [ABSTRACT FROM AUTHOR]

This study analyses data assimilative numerical simulations in an eddy-dominated western boundary current: the East Auckland Current (EAuC). The goal is to assess the impact of assimilating surface and subsurface data into a model of the EAuC via running observing system experiments (OSEs). We used the Regional Ocean Modeling System (ROMS) in conjunction with the 4-dimensional variational (4D-Var) data assimilation scheme to incorporate sea surface height (SSH) and temperature (SST), as well as subsurface temperature, salinity and velocity from three moorings located at the upper, mid and lower continental slope using a 7 d assimilation window. Assimilation of surface fields (SSH and SST) reduced SSH root mean square deviation (RMSD) by 25 % in relation to the non-assimilative (NoDA) run. The inclusion of velocity subsurface data further reduced SSH RMSD up- and downstream the moorings by 18 %–25 %. By improving the representation of the mesoscale eddy field, data assimilation increased complex correlation between modelled and observed velocity in all experiments by at least three times. However, the inclusion of temperature and salinity slightly decreased the velocity complex correlation. The assimilative experiments reduced the SST RMSD by 36 % in comparison to the NoDA run. The lack of subsurface temperature for assimilation led to larger RMSD (>1 ∘ C) around 100 m in relation to the NoDA run. Comparisons to independent Argo data also showed larger errors at 100 m in experiments that did not assimilate subsurface temperature data. Withholding subsurface temperature forces near-surface average negative temperature increments to the initial conditions that are corrected by increased net heat flux at the surface, but this had limited or no effect on water temperature at 100 m depth. Assimilation of mooring temperature generates mean positive increments to the initial conditions that reduces 100 m water temperature RMSD. In addition, negative heat flux and positive wind stress curl were generated near the moorings in experiments that assimilated subsurface temperature data. Positive wind stress curl generates convergence and downwelling that can correct interior temperature but might also be responsible for decreased velocity correlations. The few moored CTDs (eight) had little impact in correcting salinity in comparison to independent Argo data. However, using doubled decorrelation length scales of tracers and a 2 d assimilation window improved model salinity and temperature in comparison to Argo profiles throughout the domain. This assimilation configuration, however, led to large errors when subsurface temperature data were not assimilated due to incorrect increments to the subsurface. As all reanalyses show improved model-observation skill relative to HYCOM–NCODA (the model boundary conditions), these results highlight the benefit of numerical downscaling to a regional model of the EAuC. [ABSTRACT FROM AUTHOR]

On the southwest cape of the Congo craton, a subtropical carbonate bank the size of Greenland was heavily glaciated during two Cryogenian panglacial episodes spaced 10–20 Myr apart. In NW Namibia, the bank underwent crustal stretching with resultant Aegean Sea-type topography during the older and longer Sturtian glaciation (717–661 Ma). This is indicated by angular discordance between glacial and preglacial strata and diamictites sourced from all older units, including crystalline basement. In contrast, the bank was flat-topped and underwent broad thermal subsidence during Marinoan glaciation (646 ± 5–635 Ma), attested by stratal parallellism and diamictites sourced from ≤100 m stratigraphic depth. However, ≥2.0 km of relief existed on the Marinoan continental slope, where most glacial erosion and accumulation occurred. The average rates of Marinoan erosion (2.55–6.80 m/Myr, n = 190) and accumulation (2.65–7.07 m/Myr, n = 211) are indistinguishable, implying that the location in a continental promontory did not bias erosion over accumulation. The average accumulation rates for the Sturtian and Marinoan, scaled for different averaging times, including Marinoan uncertainty, are 3.95–4.93 m/Myr (n = 183) and 2.65–7.07 m/Myr (n = 190), respectively, suggesting that a Marinoan glacioeustatic coastal escarpment substituted for rift-related Sturtian basin-and-range topography. These slow rates, comparable to long-term pre-Quaternary accumulation rates on existing abyssal plains, reconcile glacial sedimentology with the feeble hydrologic cycle of snowball Earth. [ABSTRACT FROM AUTHOR]

As one of the main intermediate products of hydrogen sulfide oxidation, elemental sulfur plays an important indicator role in understanding the oxidative cycle of sulfur in the water of anoxic basins. The distribution of elemental sulfur in the water column of the Black Sea at stations located in the area of the continental slope is considered. For the first time, the concentration distributions of two forms of elemental sulfur depending on the depth in the Black Sea water were obtained: suspended elemental sulfur with a fraction of more than 0.45 μm (S0) and zero-valency sulfur (ZVS), which includes the sum of elemental sulfur (suspended and colloidal) and polysulfide sulfur. In the upper anoxic waters, the concentration of S0 noticeably increases (almost 200 times relative to the depth of 400 m) with an increase in the concentration of hydrogen sulfide and the density of water. At depths of more than 250 m, the concentration of both forms of sulfur remains almost constant (ZVS = 0.21 ± 0.03 µmol/kg, S0 = 0.05 ± 0.01 µmol/kg). A sharp increase in the concentration of S0 at the depths of 150–250 m is associated with the oxidation of hydrogen sulfide due to bacterial anoxygenic photosynthesis after sampling. The value of δ34S(ZVS) was determined in the waters of two stations Ash-26 and 149 at the depths of 450 and 600 m, respectively, which turned out to be +2.2‰ higher than δ34S(Н2S) from the same depths, which indicates the bacterial origin of elemental sulfur. [ABSTRACT FROM AUTHOR]

Submarine landslides in regions enriched with gas hydrates pose a significant threat to submarine pipelines, cables, and offshore platforms. Conducting a comprehensive regional-scale susceptibility assessment is crucial for mitigating the potential risks associated with submarine landslides in gas hydrate enrichment regions. This study conducted a preliminary exploration by presenting a probabilistic assessment framework that integrated database construction, rapid prediction model training, and landslide susceptibility assessment in hydrate enrichment regions. The database was a virtual repository constructed using numerical simulations of hydrate dissociation under various combinations of factors, including water depth, geothermal gradients, seafloor slope gradients, the seafloor temperature's rate of increase, gas hydrate saturation, and the strength and permeability of sediments. The rapid prediction model was trained using machine learning techniques, relying on the virtual database. A probabilistic assessment was performed using Monte Carlo simulations, with the landslide susceptibility determined by the rapid prediction model. The probability of landslide susceptibility exceeding a certain threshold served as an indicator for classifying the susceptibility of the study area. The proposed framework was implemented in the Shenhu area of the South China Sea, which is a representative region known for its substantial hydrate enrichment and well-developed landslides. The trained rapid prediction model for landslide susceptibility exhibited a speed advantage of over 60,000 times compared to traditional numerical calculation methods. The statistical analysis of the results in Monte Carlo simulations suggested that the landslide susceptibility was subjected to a high level of uncertainty due to limited survey data availability. Based on the probability of landslide susceptibility exceeding 0.4 in Monte Carlo simulations, the study area was classified into three zones of susceptibility: low, moderate, and high levels. [ABSTRACT FROM AUTHOR]

This work presents the results of long-term deep-water observations carried out in the southwestern Adriatic margin. Hydrodynamics and thermohaline measurements were carried out in the last 100 m of the water column using two long-term moorings placed at two different locations along the western sector of the Adriatic continental margin (open slope vs. submarine canyon). The observations, carried out over a period of almost 10 years, made it possible to define the intra- and interannual deep-water dynamics, which are mainly influenced by the passage of cold, dense water. The hydrodynamic field is influenced by seasonal behavior and varies from year to year, with no clear temporal trend or periodicity. Thermohaline properties follow hydrodynamics but also show a climatological trend toward higher temperatures and salinity. The combination and variability of preconditioning factors explains the interannual variability in dense water passage at the mooring sites triggering the formation of dense water in the northern Adriatic. The impulsive nature of the dense water flow, which is difficult to capture with sporadic oceanographic surveys, and its linkage with the large-scale atmospheric circulation make continuous monitoring essential to answer open questions about cascading processes and deep-water dynamics under a global change scenario. [ABSTRACT FROM AUTHOR]

Turbidite fans, serving as good reservoirs for petroleum accumulation, are typically formed during deep faulting periods in continental basins, particularly in steep slope zones. However, gentle slope zones are also significant and unique for the formation of turbidite fans. These turbidite fans hold immense importance in exploring concealed lithological reservoirs. Taking the Chezhen Depression of Bohai Bay Basin as an example, we conducted a comprehensive study of the turbidite fan deposits in the gentle slope zone. Our results indicate that (1) small-scale distal-source turbidite fans are a common sedimentary type in the Chezhen Depression of the Bohai Bay Basin; (2) the study area is mainly characterized by seven lithofacies; (3) there are incomplete Bouma sequences in the study interval. This study is an important turbidite investigation into continental faulted basins, and it can also provide an important reference value for exploration and development in unconventional reservoirs of the same type. [ABSTRACT FROM AUTHOR]

The southwestern tropical Pacific exhibits a complex bathymetry and represents a hot spot of internal-tide generation. Based on a tailored high-resolution regional model, we investigate for the first time the internal-tide field around the New Caledonia islands through energy budgets that quantify the coherent internal-tide generation, propagation, and dissipation. A total of 15.27 GW is converted from the barotropic to the baroclinic M2 tide with the main conversion sites associated with the most prominent bathymetric structures such as continental slopes and narrow passages in the north (2.17 GW) and ridges and seamounts south of New Caledonia (3.92 GW). The bulk of baroclinic energy is generated in shallow waters around 500 m depth and on critical to supercritical slopes, highlighting the limitations of linear semi-analytical models in those areas. Despite the strongly dominant mode-1 generation, more than 50 % of the locally generated energy either dissipates in the near field close to the generation sites or loses coherence. The remaining baroclinic energy propagates within well-defined tidal beams with baroclinic energy fluxes of up to 30 kW m -1 toward the open ocean. The New Caledonia site represents a challenge for SWOT (Surface Water and Ocean Topography) observability of balanced motion in the presence of internal tides with sea surface height (SSH) signatures >6 cm at similar wavelengths. We show for our study region that a correction of SSH for the coherent internal tide potentially increases the observability of balanced motion from wavelengths >160 km to well below 100 km. [ABSTRACT FROM AUTHOR]

The Gulf of Mexico supports many seabird species, yet data gaps describing species composition and habitat use are prevalent. We used vessel-based observations from the Gulf of Mexico Marine Assessment Program for Protected Species to identify and characterize distinct seabird assemblages in the northern Gulf of Mexico (within the U.S. Exclusive Economic Zone; nGoM). Using cluster analysis of 17 seabird species, we identified assemblages based on seabird relative density. Vessel-based surveys documented the location, species, and number of seabirds across the nGoM between 2017–2019. For each assemblage, we identified the (co-)dominant species, spatial distribution, and areas of greater relative density. We also assessed the relationship of the total relative density within each assemblage with environmental, spatial, and temporal covariates. Of the species assessed, 76% (n = 13) breed predominantly outside the nGoM basin. We identified four seabird assemblages. Two assemblages, one dominated by black tern and the other co-dominated by northern gannet/laughing gull, occurred on the continental shelf. An assemblage dominated by sooty tern occurred along the continental slope into pelagic waters. The fourth assemblage had no dominant species, was broadly distributed, and was composed of observations with low relative density ('singles' assemblage). Differentiation of assemblages was linked to migratory patterns, residency, and breeding location. The spatial distributions and relationships of the black tern and northern gannet/laughing gull assemblages with environmental covariates indicate associations with river outflows and ports. The sooty tern assemblage overlapped an area prone to mesoscale feature formation. The singles assemblage may reflect commuting and dispersive behaviors. These findings highlight the importance of seasonal migrations and dynamic features across the seascape, shaping seabird assemblages. Considering the potential far-ranging effects of interactions with seabirds in the nGoM, awareness of these unique patterns and potential links with other fauna could inform future monitoring, research, restoration, offshore energy, and aquaculture development in this highly industrialized sea. [ABSTRACT FROM AUTHOR]

Seven new species of Scalibregmatidae are described from deep waters off the east coast of Australia. Samples were collected as part of the RV Investigator voyage IN2017_V03 in May/June 2017 using a Brenke sledge and 0.25 m² box core. Sample depths reported in the present study were from the lower continental slope of about 2450 m to abyssal depths up to 4280 m. These collections provide the first scalibregmatid polychaetes to be described from deep water off Australia. The new species of Scalibregmatidae are in the genera Asclerocheilus (1), Axiokebuita (1), Oligobregma (4), and Pseudoscalibregma (1). Each of the new species is compared and contrasted with their known congeners. Asclerocheilus and Oligobregma are the largest genera of the family in terms of numbers of species; the known species of each of these genera are tabulated and compared. The Scalibregmatidae known from abyssal depths of about 3000 m and greater are reviewed and discussed. [ABSTRACT FROM AUTHOR]

Seven new species of Cirratulidae are described from deep waters off the east coast of Australia. Samples were collected as part of the RV Investigator voyage IN2017_V03 in May/June 2017 using a Brenke sledge and 0.25 m² box core. Sample depths reported in the present study were from the lower continental slope of about 2100 m to abyssal depths up to 4170 m. These collections provide the first cirratulid polychaetes to be described from deep water off Australia. The new species of Cirratulidae are in the genera Aphelochaeta (2), Chaetocirratulus (2), Chaetozone (2), and Kirkegaardia (1). Each of the new species is compared and contrasted with their known congeners. The bitentaculate Cirratulidae known from abyssal depths of 3000 m and greater are reviewed and discussed. [ABSTRACT FROM AUTHOR]

The Newfoundland and Labrador Shelves Bioregion, located on the glaciated continental shelf and adjacent continental slope of eastern Canada, is classified into units that reflect its great physiographic diversity. There are ten shelf units: bedrock zone, fjord systems, major inlet, shelf-crossing troughs, four types of offshore banks, basin, and disturbed (glaciotectonic) terrain. There are three units on the continental slope: channelized areas, trough-mouth areas, and large sedimentary drifts. A series of vignettes illustrates both the distinguishing characteristics of the principal geomorphic units and the morphologic diversity within them. A sediment mobility analysis reveals that wave- and current-generated disturbances are dominant and largely depth-controlled within the shelf units, while the south-flowing Labrador Current impacts sediment transport and mobility along the continental slope. [ABSTRACT FROM AUTHOR]

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