Continental Shelf Research Articles

Sea level and East Asian winter monsoon-controlled periodic transition of sinks in fine-grained sediments in the East China sea over the past 200 kyr

The study of critical geological processes of sediments from source to sink in the East China Sea (ECS) is of great significance for further understanding the surface processes, material cycling, and sedimentary evolution in the East Asian continental margin. Based on the high-resolution clay mineralogy and REEs in fine-grained sediments of Core CSHC-15, this study has analyzed the periodic transition mechanism of sinks in fine-grained sediments in the ECS from a source-to-sink perspective. The clay mineral provenances of Core CSHC-15 exhibited distinct periodic abrupt shifts between the Changjiang and Taiwan island over the past 200 kyr, indicating the periodic transitions of sinks in fine-grained sediments between the inner shelf of the ECS and the Okinawa Trough. When the sea level rose or fell to a critical depth (around −25 m or −50 m), the changes in the accommodation space of the continental shelf and the shelf fronts were the direct factors leading to the periodic transitions of sinks in fine-grained sediments in the ECS. The intense eccentricity cycles (100-kyr) of the clay mineral parameters of Core CSHC-15 reflected the impacts of the East Asian Winter Monsoon (EAWM). This study confirms that long-term (eccentricity and longer cycles) climate signals of the source areas can be extracted from the clastic sedimentary records of the ECS. The new finding highlights the periodic transition mechanism of sedimentary sinks in the ECS that will promote the progress of sedimentary geology since the Late Quaternary.

Quantifying predation on benthos and its overlap with bottom fishing in the NW Atlantic

AbstractContinental shelves experience many human pressures with demersal fisheries central to disturbing the ocean floor. However, ecological processes such as predation rates of benthos and their relationship with bottom fishing are often unknown for large marine ecosystems. We examined the amount of benthos consumed by 14 benthivorous fishes, the overlap between benthos predation and bottom fishing (dredge and trawl gear), and temporal trends in benthivorous fish abundance and the number of fishing trips on the northeast US continental shelf. Mean annual predation (biomass of prey removed) and 95% confidence intervals ranged from .0002 (.0001–.0003) to 3967 (1761–7112) t per 10‐min area squared grid cell and prey taxa for these benthivorous fishes. Predation and bottom fishing had overlapping footprints of activity, which were slightly stronger for dredge gear. Trophic success (ratio of prey biomass eaten to the biomass of the benthivore community per grid cell) revealed more Bivalvia, Gammaridea, and Polychaeta eaten in areas targeted by trawling with more fish biomass. In contrast, dredging did not target fish biomass, but these areas had increased (Echinoidea, Gammaridea, and other benthos) or decreased (Ophiuroidea) trophic success relative to dredging footprint, suggesting habitat preferences for benthic prey and demersal fisheries have converged rather than diverged. Despite declines in bottom fishing, recent increases in benthivorous fish abundance and growing interest in ocean floor use suggest that fisheries managers should ensure benthivores have sufficient prey resources relative to their community size and human pressures to promote long‐term sustainability of demersal fisheries and healthy ecosystems.

Taxonomy of Leodice Lamarck, 1818 (Annelida, Eunicidae) from Northeast Brazil (Tropical Southwest Atlantic Ocean) with description of a new species

Currently, Leodice has 34 species recorded worldwide. Among these, seven species are known along the Brazilian coast. This study is based on material collected during the Marine Algae project conducted in 1981 along the Continental Shelf of the State of Paraíba, at depths of 10–35 m. In this study, we present three new records: L. pellucida comb. nov. for South America, L. marcusi for northeastern Brazil, and L. unifrons for the State of Paraiba. A new species of Leodice is described from the State of Paraiba, Northeast Brazil, Leodice ivanildae sp. nov. This taxonomic study increases the number of known species of Leodice to 37, with nine occurring in Brazil. Additionally, it expands the species of Leodice known from the State of Paraiba, Brazil, from two to six.

Sediment remobilization over subaqueous sand waves: In-situ observation in the northern South China Sea

High-resolution tripod observations were conducted in a subaqueous sand-wave field in the northern South China Sea. The objective was to gain insight into the dynamic mechanism by which sandy sediments are remobilized by oceanic dynamic processes, in particular internal solitary waves and internal tides. Daily-recurring high suspended sediment concentrations were observed, likely due to lateral transport of sediments resuspended by critical reflection of diurnal internal tides at the shelf break. The passage of extreme internal solitary waves results in resuspension of sediments from the seabed and ejection of these sediments out of the boundary layer. The resuspension of sediments from the seabed is controlled by current-induced strong bed shear stress, while the ejection of sediments out of the bottom boundary layer is driven by the compression and subsequent expansion of the mixing layer, together with the developments of the separation bubbles behind the internal solitary waves. These findings provide new insights into understanding the dynamic mechanism of sediment remobilization by internal solitary waves. Moreover, they contribute to our understanding of the migration of subaqueous sand waves.

Nonnegligible contribution of terrigenous sediment inputs from local small watersheds to west regions of the Pearl River Estuary, northern South China Sea shelf

As a crucial “sink” for terrigenous material entering the ocean, provenance of sediments within the coastal zone and continental shelf sea regions holds significant scientific importance in the investigation of global material cycling. Environmental magnetism was proved as an effective and rapid approach for sediment source identification. Detail and systematic magnetic measurements were performed for surface sediment samples collected from the mega Pearl River, local small rivers (Tan, Moyang and Jian rivers) of west Guangdong, coastal zone (CZ) and continental shelf (CS) to analyze the contribution of local small watersheds to marine sediments. The results indicate that detrital river input magnetite and hematite are coexisted in both CZ and CS sediments. Compared to CZ sediments, relatively higher concentration of hematite and finer grain size of magnetite are appeared at CS sediments. By comparing of magnetic parameters, it was inferred that magnetic minerals from the Pearl and Tan rivers are transported and deposited on the coastal zone by Guangdong longshore current. Meanwhile, sediment magnetic parameters in the Moyang and Jian Rivers are similar to the CS sediments, implying the two rivers-sourced materials were directly transported and deposited at the CS due to their narrow and restricted estuaries, and/or the CS preserves the residual deposits from the two rivers formed during the Last Glacial. Except for the Pearl River, sources of local small rivers significantly contribute to marine sediments at the coastal zone and continental shelf.

Different pacemakers of marine organic carbon burial in the North Yellow Sea from the early to late Holocene

Marginal seas play a crucial role in the global carbon cycle, contributing approximately 20% of the net CO2 uptake by the world's oceans. The North Yellow Sea (NYS), a semi-enclosed marginal sea in the western Pacific Ocean, serves as a significant carbon sink influenced by factors such as sea level changes, monsoon dynamics, ocean currents, and El Niño-Southern Oscillation (ENSO) activity. This study examines a 538 cm-long sediment core W03 from the NYS (10.3 kyr BP to present). We analyzed Organic Carbon (OC) proxies, including total organic carbon (TOC), the stable carbon isotope (δ13C) of TOC, total nitrogen (TN) and marine-produced lipid biomarkers. Our findings demonstrate a strong correlation between OC burial and sea-level fluctuations during the early Holocene, driven by the exposure of the continental shelf. During the mid-Holocene, the intrusion of the Yellow Sea Warm Current increased salinity and temperature conditions and nutrient levels of sea water, thereby enhancing marine OC burial. Over the last 3.3 kyr BP, ENSO variability and intensified East Asian Winter Monsoon (EAWM) strengthened the coastal currents, contributing to better OC preservation. Additionally, human activities on the surrounding mainland increased terrestrial input, altering the OC burial. The heightened activity of the Kuroshio Current also introduced more saline and warm water masses into the NYS, impacting phytoplankton productivity and community structure, as indicated by increased C37 alkenones. This study highlights the complex interplay of geological factors in OC burial processes within the NYS, providing valuable insights into OC dynamics in marginal seas under the impact of global change.

Toward Parameterizing Eddy-Mediated Transport of Warm Deep Water across the Weddell Sea Continental Slope

Abstract The transport of warm deep water (WDW) onto the Weddell Sea continental shelf is associated with heat flux and strongly contributes to the melting of Antarctic ice shelves. The small radius of deformation at high latitudes makes it difficult to accurately represent the eddy-driven component of onshore WDW transport in coarse-resolution ocean models so that parameterization becomes necessary. The Gent and McWilliams/Redi (GM/Redi) scheme was designed to parameterize mesoscale eddies in the open ocean. Here, it is assessed to what extent the GM/Redi scheme can generate a realistic transport of WDW across the Weddell Sea continental slope. To this end, the eddy parameterization is applied to a coarse-resolution idealized model of the Weddell Sea continental shelf and slope, and its performance is evaluated against a high-resolution reference simulation. With the GM/Redi parameterization applied, the coarse model simulates a shoreward WDW transport with a heat transport that matches the high-resolution reference and both the hydrographic mean fields and the mean slopes of the isopycnals are improved. A successful application of the GM/Redi parameterization is only possible by reducing the GM diffusivity over the continental slope by an order of magnitude compared to the open ocean value to account for the eddy-suppressing effect of the topographic slope. When the influence of topography on the GM diffusivity is neglected, the coarse model with the parameterization either under- or overestimates the shoreward heat flux. These results motivate the incorporation of slope-aware eddy parameterizations into regional and global ocean models. Significance Statement Mesoscale eddies drive warm water across the continental slope and onto the continental shelf of the Weddell Sea, where it melts the adjacent Antarctic ice shelves. This process is not resolved in ocean models employing a coarse horizontal resolution akin to state-of-the-art climate models. This work addresses this issue by modifying and applying a well-established eddy parameterization to this specific case. The parameterization works particularly well when it accounts for the effect of sloping topography, over which eddy transports are weaker. We expect this modification also to be of benefit to regional and global models.

Cross-Shelf Exchange in Prograde Antarctic Troughs Driven by Offshore-Propagating Dense Water Eddies

Abstract This study examines the link between near-bottom outflows of dense water formed in Antarctic coastal polynyas and onshore intrusions of Circumpolar Deep Water (CDW) through prograde troughs cutting across the continental shelf. Numerical simulations show that the dense water outflow is primarily in the form of cyclonic eddies. The trough serves as a topographic guide that organizes the offshore-moving dense water eddies into a chain pattern. The offshore migration speed of the dense water eddies is similar to the velocity of the dense water offshore flow in the trough, which scaling analysis finds to be proportional to the reduced gravity of the dense water and the slope of the trough sidewalls and to be inversely proportional to the Coriolis parameter. Our model simulations indicate that, as these cyclonic dense water eddies move across the trough mouth into the deep ocean, they entrain CDW from offshore and carry CDW clockwise along their periphery into the trough. Subsequent cyclonic dense water eddies then entrain the intruding CDW further toward the coast along the trough. This process of recurring onshore entrainment of CDW by a topographically constrained chain of offshore-flowing dense water eddies is consistent with topographic hotspots of onshore intrusion of CDW around Antarctica identified by other studies. It can bring CDW from offshore to close to the coast and thus impact the heat flux into Antarctic coastal regions, affecting interactions among ocean, sea ice, and ice shelves. Significance Statement Troughs cutting across the Antarctic continental shelf are a major conduit for the transport of dense shelf water from coastal formation regions to the shelf break. This study describes a process in which clockwise-spinning eddies moving offshore in prograde troughs successively entrain filaments of relatively warm Circumpolar Deep Water from offshore across the entire shelf and into the coastal region. This eddy-induced transport provides a new understanding of the shelf edge exchange process identified in previous studies and a mechanism for further onshore intrusion of the warm Circumpolar Deep Water over parts of the Antarctic shelf. The resultant onshore heat flux could potentially bring a substantial amount of heat from offshore into the coastal region and thus affect ice–ocean interactions through melting sea ice and ice shelves.

A new fusulinid species from the early Permian of northwestern Peninsular Malaysia: Evidence of the Artinskian warming event in the eastern Peri-Gondwanan Sibumasu Block

A new species of Crenulosepta, i.e., Crenulosepta perlisensis Vachard and Fassihi sp. nov., is described from a Cisuralian (Lower Permian) sandy limestones and calcareous sandstones in the Kubang Pasu Formation in northwestern Peninsular Malaysia, which forms part of the Peri-Gondwanan Sibumasu Block. Previous Malaysian authors reported the occurrence of Monodiexodina shiptoni and Monodiexodina sutschanica from the same area. The findings of this study provide a better overview of the Cisuralian fusulinid fauna found in this region. The presence of Crenulosepta confirms that the age of the uppermost part of the Kubang Pasu Formation is Artinskian, rather than extending into the Kungurian as previously recognized. The uppermost part of the Kubang Pasu Formation with its impoverished genus and species diversity is located just above the cold water brachiopods and diamictite beds. It indicates that during the Asselian (earliest Cisuralian), the northwestern Peninsular Malaysia was still part of the Gondwana continental shelf. During the late Early Permian, northwestern Peninsular Malaysia, as part of the eastern Cimmerian Continent, was located in a low latitude subtropical region of the paleo-equatorial tropical Tethyan Realm. The microfacies analysis of the Kubang Pasu Formation suggests a very high-energy, warm shallow marine environment of the inner ramp (e.g., sand shoals and banks).

Preservation of Organic Carbon Associated with Iron on Continental Shelves Influenced by Hydrodynamic Processes.

Understanding the environmental fate of organic carbon associated with iron (OC-Fe) is critically important for investigating OC preservation in aquatic systems. Here, we first investigate 13C and 14C isotopes of OC-Fe within grain size-fractionated sediments retrieved from the East China Sea and estimate their sources and reactivities of OC-Fe through isotope-mixing models and thermal pyrolysis approaches in order to reveal the fate of OC-Fe on continental shelves influenced by hydrodynamic processes. Our results show that the OC-Fe proportion in total OC (fOC-Fe) in the sortable silt fractions (20-63 μm) is the highest among three grain size fractions, likely suggesting that hydrodynamics may enhance the iron protection on OC. In addition, Δ14COC-Fe values fall within the range of from -358.73 to -64.03‰, and both Δ14COC-Fe values and ancient OC-Fe% exhibit strong positive linear relationships with fOC-Fe. This emphasized that the hydrodynamic processes may cause the ancient OC to be tightly associated with Fe, accompanying OC-Fe aging. Our findings shed new light on the preservation of OC-Fe in marginal seas to advance the recognition of carbon "rusty sinks" in seafloor sediments.

Variation in Isotopic Trophic Niche of Sablefish (Anoplopoma fimbria) and Shortraker Rockfish (Sebastes borealis) in the Northeast Pacific

Sablefish (Anoplopoma fimbria, Anoplopomatidae) and shortraker rockfish (Sebastes borealis, Sebastidae), co-occur in deepwater marine habitats in the northeast Pacific. Both species are economically valuable, but their ecologies are not well known. We used stable isotope analysis of carbon and nitrogen to explore isotopic niches of A. fimbria and S. borealis in two distinct locations—a deep strait in the inside passage area and an open coastal area of the continental shelf, both in southeast Alaska, USA. Anoplopoma fimbria and S. borealis exhibited similar positions of isotopic niches based on nitrogen and carbon isotopic ratios, suggesting potential interspecific competition, especially in the inside location. In addition, S. borealis had a smaller niche breadth compared to A. fimbria in the coastal location. Both species had enriched nitrogen and carbon isotopic ratios in the inside location compared to the coastal location. Differences in isotopic niches between these two locations suggest the possibility of location-specific variation in isotopic niches of these two species of widespread, abundant deepwater fishes.

Arctic Continental-Shelf Sediment Dynamics.

Sediments covering Arctic continental shelves are uniquely impacted by ice processes. Delivery of sediments is generally limited to the summer, when rivers are ice free, permafrost bluffs are thawing, and sea ice is undergoing its seasonal retreat. Once delivered to the coastal zone, sediments follow complex pathways to their final depocenters-for example, fluvial sediments may experience enhanced seaward advection in the spring due to routing under nearshore sea ice; during the open-water season, boundary-layer transport may be altered by strong stratification in the ocean due to ice melt; during the fall storm season, sediments may be entrained into sea ice through the production of anchor ice and frazil; and in the winter, large ice keels more than 20 m tall plow the seafloor (sometimes to seabed depths of 1-2 m), creating a type of physical mixing that dwarfs the decimeter-scale mixing from bioturbation observed in lower-latitude shelf systems. This review summarizes the work done on subtidal sediment dynamics over the last 50 years in Arctic shelf systems backed by soft-sediment coastlines and suggests directions for future sediment studies in a changing Arctic. Reduced sea ice, increased wave energy, and increased sediment supply from bluffs (and possibly rivers) will likely alter marine sediment dynamics in the Arctic now and into the future.

Time series modeling of coastal fishery landings on the Southwestern Atlantic shelf: Influence of environmental drivers

AbstractTime‐series modeling of fisheries provides insights into stock tendencies and enables short‐term forecasting of landings, aiding decision makers in establishing management priorities. The Rio de la Plata Estuary and its maritime front sustain valuable fisheries for Argentina and Uruguay, with striped weakfish (Cynoscion guatucupa), whitemouth croaker (Micropogonias furnieri), and Argentine hake (Merluccius hubbsi) historically representing highest catches. However, their landings have declined in recent decades. To support resource management, we investigated the effectiveness of Autoregressive Integrated Moving Average (ARIMA) models in capturing fishery landing dynamics and providing reliable short‐term predictions. The best models exhibited a good fit and accurately captured the overall trends of landings. Residual variability unaccounted for by the model was analyzed in relation to time‐lagged environmental conditions. A wavelet coherence analysis was employed to examine the effect of the most significant variables on landings. Results revealed that environmental conditions affect differentially landings of each species as a result of their particular ecological traits. Turbidity and salinity affected mainly M. furnieri, which inhabits the innermost part of the estuary. Additionally, C. guatucupa, inhabiting the outer estuary and coastal region, exhibited a stronger association with river runoff compared to M. hubbsi, which inhabits the continental shelf. This study provides the first evidence of ARIMA models' reliability in representing the temporal evolution of catch in these fisheries, offering valuable tools for short‐term landings forecasting and facilitating sustainable management. Wavelet analysis findings will also contribute to enhancing our comprehension of trends in the correlation between environmental conditions and commercial landings.

Glacial history of the King Haakon trough system, sub-Antarctic South Georgia

The glaciated island of South Georgia in the sub-Antarctic is a key area for climate reconstructions, because it is positioned in the Southern Ocean amidst the core belt of the Southern Westerlies and the main fronts of the Antarctic Circumpolar Current. This makes it particularly susceptible to changes in local, regional, but also Southern Hemisphere-wide climate conditions. Marine-geological records recovered from its continental shelf therefore offer unique potential to constrain how ice masses in this part of the Southern Ocean responded to Quaternary climate change, but despite this, little glacial-geomorphological and sedimentological research has been done offshore South Georgia. Here, we present a new suite of glacial landforms, identified from high-resolution bathymetry data, supplemented with acoustic facies from sub-bottom profiles, in order to reconstruct the pre-Holocene glacial history of the King Haakon Trough System on the southwestern South Georgia continental shelf. Our data show numerous landforms common for phases of ice advance and retreat, which are interpreted to document the confluence of two major trunk glaciers during peak glaciation. Progressively elongated linear bedforms imply accelerated ice flow and/or softer sediment substrate towards the shelf edge and suggest that the South Georgia Ice Cap experienced streaming ice and behaved similarly to other palaeo-ice sheets. A grounding-zone wedge close to the shelf edge marks the position of maximum ice extent during a peak glaciation, while clusters of recessional moraines and three large morainal banks indicate repeated phases of staggered retreat. Multiple extensive ice advances are indicated by stacked till sequences within the sub-bottom profiles of the mid- and outer shelf. The second-to-last till generation appears to be slightly more extensive than the most recent glacial till, and could suggest that South Georgia may have had a similar glacial evolution to other sub-Antarctic islands. This paper complements two studies focusing on the Holocene depositional environments and their associated sedimentary processes in the same trough system, in an effort to elucidate an important part of the Quaternary evolution of South Georgia's marine environment.

Ecosystem risk from human use of ocean space and resources: A case study from the Norwegian coast

Coastal and adjacent shelf waters are generally highly productive ecosystems harboring important ecological processes and exposed to a range of anthropogenic pressures from land-based and marine sectors. Ensuring that the cumulative pressures from human activities do not cause unacceptable, permanent harm to the ecosystem is challenging but crucial for sustainable management of these regions. Linkage frameworks and ecological risk assessments have proven to be useful tools for holistic evaluations of cumulative human pressures as a guide to managers and policy makers for prioritization of risk factors. Here, we present the first holistic assessment of ecosystem risk from human activities along the Norwegian coast. Pressures from coastal sectors are identified and weighted by the exposure to and potential impact on ecosystem components following the ODEMM (Options for Delivering Ecosystem-based Marine Management) framework. We focus on four coastal regions with contrasting scales of human activities. Two southern regions with multiple anthropogenic activities are associated with higher cumulative risk of negative impacts compared to northern areas where less extensive activities have a lower potential of harming the coastal ecosystems. Despite latitudinal differences in human use of the coastline, the pressures and ecosystem components associated with the greatest risk of cumulative impacts are relatively similar between the regions. Contaminants and underwater noise stand out as high-risk pressures, associated with multiple sectors with a high spatiotemporal footprint and with the potential to negatively impact a range of ecosystem components. Nevertheless, a confidence assessment also highlights the need for more in-depth analysis on the input, spread and effect of these pressures on coastal ecosystems. We discuss strengths and weaknesses of the risk assessment framework and suggest new directions which may enhance the utility and uptake of such assessments for sustainable management of coastal ecosystems.

Using joint species distribution modelling to predict distributions of seafloor taxa and identify vulnerable marine ecosystems in New Zealand waters

AbstractEffective ecosystem-based management of bottom-contacting fisheries requires understanding of how disturbances from fishing affect seafloor fauna over a wide range of spatial and temporal scales. Spatial predictions of abundance for 67 taxa were developed, using an extensive dataset of faunal abundances collected using a towed camera system and spatially explicit predictor variables including bottom-trawl fishing effort, using a Joint Species Distribution Model (JSDM). The model fit metrics varied by taxon: the mean tenfold cross-validated AUC score was 0.70 ± 0.1 (standard deviation) for presence–absence and an R2 of 0.11 ± 0.1 (standard deviation) for abundance models. Spatial predictions of probability of occurrence and abundance (individuals per km2) varied by taxon, but there were key areas of overlap, with highest predicted taxon richness in areas of the continental shelf break and slope. The resulting joint predictions represent significant advances on previous predictions because they are of abundance, allow the exploration of co-occurrence patterns and provide credible estimates of taxon richness (including for rare species that are often not included in more commonly used single-species distribution modelling). Habitat-forming taxa considered to be Vulnerable Marine Ecosystem (VME) indicators (those taxa that are physically or functionally fragile to anthropogenic impacts) were identified in the dataset. Spatial estimates of likely VME distribution (as well as associated estimates of uncertainty) were predicted for the study area. Identifying areas most likely to represent a VME (rather than simply VME indicator taxa) provides much needed quantitative estimates of vulnerable habitats, and facilitates an evidence-based approach to managing potential impacts of bottom-trawling.

Diel vertical migration and seamount stepping stones promote species connectivity from coastal to offshore insular systems in the Tropical Southwestern Atlantic

AbstractThe recruitment of marine species in isolated oceanic island systems can be challenged by prevailing currents, as exemplified by the Tropical Southwestern Atlantic. In this region, the Fernando de Noronha ridge hosts several seamounts, the Rocas Atoll and the Fernando de Noronha Archipelago, which are home to great marine biodiversity. However, along the ridge, the central branch of the South Equatorial Current (cSEC), flowing westward, poses a challenge to the recruitment of organisms toward Fernando de Noronha. To unveil critical insights into the intricate processes shaping biodiversity in these insular ecosystems, we use a dispersal Lagrangian tool to explore the role of diel vertical migration (DVM) to depth strata influenced by the South Equatorial Undercurrent (SEUC), which flows eastward bellow the cSEC, in shaping species dispersal and metacommunity dynamics. Our results show that while not a direct journey, the DVM into SEUC‐influenced strata increases the possibility that the seamounts and the Rocas Atoll act as stepping stones between the continental shelf and Fernando de Noronha. Propagules of organisms originating primarily from the continental shelf are transported to the western seamounts of the ridge. Upon reaching the western seamounts, organisms can find suitable habitats to recruit. The progeny of these communities that migrate to SEUC‐influenced strata have the opportunity to reach suitable habitats at the Rocas Atoll and the Eastern seamounts, ultimately connecting to the Fernando de Noronha archipelago. These results provide scientific fundaments for the development of a functional network of marine protected areas in the Tropical Southwestern Atlantic.

Sedimentation record of a complete glacial-interglacial cycle: Down-slope deposits, contourites and plumites of the North Sea trough mouth fan

Trough mouth fans (TMFs) are major submarine depocentres that form in front of ice streams advancing onto the continental shelf, and they provide extensive records of past glaciations and ice-sheet dynamics. However, early research about TMFs was conducted using primarily 2D seismic data, which limits the insights on the deposit's geometries and internal structures and more recent studies using 3D data have focused on the general depositional history of TMFs. Here, we assess the spatial and temporal changes of the glacio-marine landforms and deposits throughout the last glacial-interglacial cycle (Marine Isotope Stage (MIS) 6 to 1, ∼130 ka to present) recorded in a >550 m thick progradational sequence. We use 3D reflection seismic data with significant vertical resolution (up to 2 m) imaging over 14000 km2 from the uppermost North Sea Fan (NSF) to document the seismic stratigraphy and sedimentary processes, by combining horizon picking and geomorphological analyses. The studied interval comprises five mappable units, four on the slope and one on the shelf, spanning from the modern seabed down to the top of the Tampen Slide (∼130 ka). Five different channel types (here included slide scars), as well as contourite and plumite packages are described based on their seismic facies, morphology, geometry, and stratigraphical position. We propose that contour currents are responsible for sediment delivery after the Tampen Slide deposition during the interglacial period before the onset of the Last Glacial Maximum, when high meltwater influx from the shelf produced turbidites. Sedimentation became debris-flow-dominated towards the end of the period of shelf-edge glaciation. The deglacial interval is characterized by the deposition of plumites on the slope. On the shelf, subglacial tills are deposited during both glacial and deglacial periods. We calculate an average sedimentation rate of <1 m/kyr during the interglacial (MIS 5-3), and around 50–65 m/kyr during the glacial and deglacial periods (MIS2-early MIS1). Thus, we document a change of two orders of magnitude in sedimentation rate during a glacial cycle on the slope of a glaciated margin.

Resource partitioning influences levels of toxic trace elements in sympatric tropical seabirds

Morphologically similar species that occupy resource-limited environments tend to differ in their ecological traits in order to coexist, which may result in differential exposure to environmental threats. For instance, partitioning of feeding resources may influence contaminant exposure and bioaccumulation in marine predators through different diets or foraging habitats. Here, we sampled three tropical seabird species breeding in sympatry in the southwestern Atlantic Ocean for blood and feather trace element concentrations (As, Hg, Cd, Pb), and assessed their foraging ecology with bio-logging (GPS tracks and time-depth recorders), analysis of regurgitated prey, and carbon and nitrogen stable isotope mixing models. Red-billed tropicbirds (Phaethon aethereus), brown (Sula leucogaster) and masked (S. dactylatra) boobies differed in their preferred foraging locations, the range of foraging trips, diving parameters and diets. In addition, interspecific differences were detected in blood or feathers for all trace elements analyzed, suggesting influence of the differences observed in diet and space use. Red-billed tropicbirds had the largest foraging range over the continental shelf and over the slope, suggesting lower exposure to continental sources of metals. Brown and masked boobies had higher Hg concentrations than tropicbirds, higher δ15N values (a proxy for trophic level), and δ15N correlated with Hg levels, suggesting biomagnification of Hg along the food chain. Nonetheless, red-billed tropicbirds showed comparable levels of As and Cd in blood or feathers, and higher levels of Pb in both tissues in comparison to boobies, which may suggest overall exposure of seabirds in the region, through their diets and foraging areas. Resource partitioning is critical for allowing coexistence of different seabird species in shared breeding sites where they act as central-place foragers. Nonetheless, in scenarios of environmental pollution, these species-specific strategies lead to differential bioaccumulation, and thus distinct effects of pollution on populations are expected.

Environmental Life Cycle Assessment of multi-use of marine space: A comparative analysis of offshore wind energy and mussel farming in the Belgian Continental Shelf with terrestrial alternatives

The Belgian Continental Shelf is a highly used part of the North Sea, where many different maritime activities thrive, such as shipping, fishing and energy production. Offshore wind energy in particular has gained importance in the region and concessions zones are allowed to be combined with aquaculture activities. It is unclear what the environmental impact of maritime multi-use is, from a life-cycle perspective, where there is potential to create synergies in the value chains, and how similar the impact compares to currently used alternatives. Therefore, this study performs a Life Cycle Assessment on a combination of a full scale existing wind energy farm and a mussel farm design. When analyzing the net environmental impact results of the multi-use offshore farm at the level of three areas of protection, i.e. human health, ecosystem quality and natural resources, it shows that the mussel farm contributes relatively the most to the net impacts, while the majority of the avoided burdens are attributed to the wind farm. Mainly the supply chain of materials required to manufacture its components followed by the operational activities of the multi-use offshore farm contribute to the environmental footprint. Moreover, taking advantage of joint activities, i.e. combined transport between the wind and mussel farm during operational activities (Scenario 1) and at decommissioning phase (Scenario 2) did not show a significant reduction in the overall net impacts of a multi-use farm. The life cycle assessment results of a multi-use offshore farm are furthermore compared with relevant terrestrial benchmarks in Belgium, i.e. nuclear energy and pork meat production. While the benchmarks have a high burden on the area of protection ecosystem quality due water and land use requirements, the multi-use farm mainly impacts the remaining areas of protection, i.e. human health and natural resources, again as a consequence of the burdens of its supply chain. This study reveals the potential of offshore multi-use farms in terms of environmental sustainability, offering valuable insights to policy-makers and value chain actors, and generally contributes to well-informed decision-making.