Continental Shelf Research Articles

Morphological Characteristics of an Open Shelf Ridge at Rio Grande do Norte Continental Shelf, NE Brazil

Morphological Characteristics of an Open Shelf Ridge at Rio Grande do Norte Continental Shelf, NE Brazil

Is the Commission on the Limits of the Continental Shelf Mandated to Consider Submissions from Non-States Parties to the United Nations Convention on the Law of the Sea?

Abstract This article scrutinises the mandate of the Commission on the Limits of the Continental Shelf (Commission) to consider submissions from non-States Parties to the 1982 United Nations Convention on the Law of the Sea (LOSC). It challenges the prevailing viewpoints that exclude non-State Parties from the submission process, proposing a nuanced approach that privileges legal orthodoxy and political feasibility. It proposes that LOSC Article 76, containing the Commission’s mandate, can be interpreted as a stipulation pour atrui, conferring rights to third States in accordance with Article 36 of the Vienna Convention on the Law of Treaties. Innovatively, this possibility is explored here with a particular concern for preserving the balance of interests achieved in 1982. Its timeliness is due to the intentions of making a submission recently expressed by the United States, a non-State Party.

Fish distribution shifts due to climate change in the Northeast Atlantic: Using a hierarchical filtering approach on marine-estuarine opportunist species

Marine-estuarine opportunist (MEO) species are fish that occur in the continental shelf and use estuaries and/or shallow coastal areas as nurseries. These commercially important resources are facing significant environmental modifications caused by direct and/or indirect anthropogenic climate change effects. In this study, we investigated the directionality and the magnitude of the distribution shifts (i.e., range size, gravity centroids, and margins) in marine environment suitability for six main MEO fish species within the Northeast Atlantic expected for the end of the 21st century. In the framework of this study, we have distinguished ‘sub-boreal’ from ‘sub-tropical’ species. The ‘hierarchical filters’ concept was adopted for modelling the potential species distributions and combined the predictions of i) a bioclimatic model with ii) a habitat model. The bioclimatic model is based on large-scale and time-variant variables while variables of the habitat model are fine-grained and time-invariant. Two Intergovernmental Panel on Climate Change (IPCC) scenarios are tested: an intermediate (SSP2-4.5) and a pessimistic one (SSP5-8.5). We applied this framework using international databases of biodiversity occurrences, ensemble forecasting producing consensual predictions, and innovative indices of distribution shifts. A visible north-westward shift was predicted for all six species in our study area. However, the northward expansion was greater for ‘sub-tropical’ than for ‘sub-boreal’ species due to faster gravity centroid displacement shifts and faster margins shifts. These range shifts may lead to major ecological impacts (e.g., changes in recruitment to estuarine and coastal nurseries, as well as changes in spawning grounds) that may alter populations' connectivity.

Monthly and Interannual Variations in Upwelling and Chlorophyll off the Vietnam Coast in Summer Based on Deep Learning

AbstractThe deep learning technique is used to automatically identify upwelling regions off the Vietnam coast using Sea Surface Temperature (SST) data from satellite imagery. After delineating these upwelling areas, this study is pioneering in deriving the upwelling probability off the Vietnam coast, pinpointing two significant upwelling hotspots. To deepen the understanding of the individual impacts of wind and sea surface height anomalies on monthly and spatial variations in upwelling probability and chlorophyll distribution, the Empirical Orthogonal Function method was employed to analyze this data set. The upwelling probability demonstrates a close relationship with wind and sea surface height anomalies, while chlorophyll concentration correlates with the strength of the southwesterly wind. The southwesterly wind, Ekman pumping, eddy dipole, and northeastward jet have been identified as key drivers of the formation and spatial variability of upwelling in summer, albeit with varying contributions to different parts of the coastal region. The distribution of upwelling probability correlates with chlorophyll variation off the northern Vietnam coast. High chlorophyll concentration off the southern Vietnam coast is primarily influenced by the southwesterly wind that carries the Mekong River plume eastward. Furthermore, two abnormal scenarios in upwelling and chlorophyll concentration during 2010 and 2018 were analyzed, attributed to the abnormal southwesterly monsoon and coastal circulation influenced by an El Niño event and a weak La Niña event with a positive Indian Ocean Dipole, respectively. This study elucidates the dynamic processes underlying the intricate chlorophyll distribution over the continental shelf, which is influenced by both the river plume and upwelling.

Yucatan shelf’s larval density and distribution of Auxis spp. and Caranx crysos are primarily driven by regional upwelling and seasonality

The extensive Yucatan Shelf (YS) in the southern Gulf of Mexico provides habitat for many marine species and supports important fisheries. A striking feature is the regional upwelling along its eastern margin due to the interaction of the Yucatan Current with the western slope of the Yucatan Channel. Coupled with easterly winds, the upwelled water fertilizes the shelf and contributes to high productivity in an otherwise oligotrophic region. However, an understanding of the role that regional upwelling plays on fish spawning and larval fish distributions is limited. We describe the distribution, frequency of occurrence, and densities of two commercially important neritic species (Auxis spp. and Caranx crysos) with contrasting life histories (different adult habitat, neritic vs. neritic and oceanic, and with spawning peak vs. year around spawner). The relationship between larval density and environmental variables, including upwelling indicators, was examined for three oceanographic cruises that covered the entire YS and which were held during summer through fall (2015, 2016 and 2018). None (Auxis spp.) or very few (C. crysos) larvae were caught during the late fall cruise in November. The highest densities of both taxa were found during the summer cruise in July, consistent with their spawning periods. Both species were mostly distributed beyond the 40 m isobath, and the highest densities were found over the central and eastern shelf. Generalized additive models indicated that Auxis spp. and C. crysos densities were correlated with low chlorophyll a concentration (located in the outer shelf) and a shallower 22.5 °C isotherm (a proxy for upwelling), indicating that regional upwelling was associated with higher larval fish densities.

STATE GUARANTEES FOR THE SAFETY OF OFFSHORE OIL AND GAS INSTALLATIONS WITHIN THE FRAMEWORK OF INTERNATIONAL LAW AND IMMIGRATION LAW - DOI: 10.12818/P.0304-2340.2024v85p201

Offshore oil and gas installations are independent structures that are vulnerable to disturbances and threats. Like ships, offshore oil and gas installations also have national flags and legal instruments that protect them. Under international law, offshore oil and gas installations are protected by the Rome Protocol for the Suppression of Unlawful Acts against the Safety of Fixed Platforms Situated on the Continental Shelf 1988. It is noted that there have been several incidents of disturbances and threats that have occurred at offshore oil and gas installations around the world. Some events are well recorded and known to the public, while some events are not public consumption. So far, offshore oil and gas installation operators have received legal guarantees for the security of their installations both on the high seas and in the sea territory of a country based on international law, territorial law and the inherent law according to the citizenship of the offshore oil and gas installation. Through this paper, the author aims to explain the potential threats and disturbances at offshore oil and gas installations and concrete examples of events that have occurred. Another aim is to explain how international legal instruments and immigration law protect offshore oil and gas installations from these threats and disturbances. Through normative legal research, this paper describes a series of threats and disturbances and the international and national laws that have emerged to protect them and their application in the field.

From source to sink: part 2-seasonal dispersion of microplastics discharged in the NW Mediterranean Sea by the Rhone River in southern France.

As the largest individual contributor of freshwater inflow to the basin, the Rhone River is likely to be one of the main sources of microplastics (MPs) to the Mediterranean Sea. In order to predict the fate of MPs discharged by the Rhone River, an innovative 3D Lagrangian dispersion of its particles associated with vertical velocities was modeled in Mediterranean ocean currents. Through winter and summer scenarios, the seasonal variability of transfers and the corresponding accumulation areas were depicted in the Northwestern Basin according to hydrodynamic conditions on the continental shelf of the Gulf of Lion and to the frontal dynamics from the Pyrenees to the North Balearic fronts. Our results indicated that MP transfers were driven by mesoscale and sub-mesoscale structures, resulting in steep concentration gradients across fronts during summer, while winter energetic mixing favored a more efficient and homogeneous spreading. After a year of drift, high MP retention (up to 50%) occurred in the coastal zone of the Gulf of Lion near the river mouth, with a large contribution of sinking MPs and an increase in stranding during the highest freshwater inflows of the winter season. Conversely, up to 60% of the floating MPs were exported to the Algerian Basin and then to the Eastern Mediterranean. This west-to-east transfer led to significant stranding on the islands, prevailing on the northern coasts of the Balearic Islands in winter (6% of floating inputs) and on the western coasts of Corsica and Sardinia in summer (13%). The southern Mediterranean coasts, from Algeria to Tunisia, represented also a major sink for floating debris with stranding ranging from 9 to 35% of MPs discharged in winter and in summer, respectively. We estimated that 3.5 to 5 t of the Rhone MPs remained in the surface layer at the end of the year, with high concentrations in the Ionian Sea.

Assessing the impact of sea level rise on maritime entitlement and delimitation: an interdisciplinary investigation through legal and technical analysis

This paper delves into the complexities of maritime delimitation in the context of sea level rise (SLR) and ice-covered regions, examining several factors and legal implications. Through academic discussion and technical analysis, the adjustments is required in approaches to the Exclusive Economic Zone and the continental shelf boundaries’ delimitation amidst SLR, while the different models adopted by adjacent and opposite states are presenting. As a result, the paper provides a comprehensive overview of common issues surrounding baseline determination, particularly in relation to SLR and the challenges posed by off-shore features. Legal dynamics concerning ‘submarine ridges’ versus ‘oceanic ridges’ are explored, highlighting the complexities inherent in maritime boundary delineation. Additionally, the dynamics of basepoint selection in ice-covered regions is investigated, emphasizing essential criteria for navigation and offering case studies from the Antarctic and Arctic here. Through this exploration, the paper contributes to a deeper understanding of the challenges and considerations involved in maritime delimitation amidst SLR, offering valuable insights from both technical and legal perspectives.

Expanding seawater carbon dioxide and methane measuring capabilities with a Seaglider

Abstract. Warming, ocean acidification, and deoxygenation are increasingly putting pressure on marine ecosystems. At the same time, thawing permafrost and decomposing hydrates in Arctic shelf seas may release large amounts of methane (CH4) into the water column, which could accelerate local ocean acidification and contribute to climate change. The key parameters to observing and understanding these complex processes and feedback mechanisms are vastly undersampled throughout the oceans. We developed carbon dioxide (CO2) and CH4 gliders, including standard operational procedures, with the goal that CO2 and CH4 measurements will become more common for glider operations. The Seagliders with integrated Contros HydroC CO2 or CH4 sensors also include conductivity, temperature, depth, oxygen, chlorophyll a, backscatter, and fluorescent dissolved organic matter sensors. Communication via satellite allows for near-real-time data transmission, sensor adjustments, and adaptive sampling. Several sea trials with the CO2 Seaglider in the Gulf of Alaska and data evaluation with discrete water and underway samples suggest nearly “weather-quality” CO2 data as defined by the Global Ocean Acidification Network. A winter mission in Resurrection Bay, Alaska, provided the first insights into the water column inorganic carbon dynamics during this otherwise undersampled season. The CH4 Seaglider passed its flight trials in Resurrection Bay but needs to be tested during a field mission in an area with CH4 concentrations beyond background noise. Both sensing systems are available to the science community through the industry partners (Advanced Offshore Operations and -4H-JENA engineering GmbH) of this project.

Spatiotemporal distribution of sedimentary chloropigments and organic carbon in a shelf sea ecosystem, with a focus on the cold water mass

The Yellow Sea is one of the most thoroughly studied shelf seas in the northwestern Pacific. However, many aspects of the northern Yellow Sea sediments remain poorly understood. Sedimentary chloropigments and total organic carbon (TOC) are crucial components that indicate benthic primary productivity and ecosystem functioning in the marginal sea system. The present study investigated the temporal and spatial variations of sediment chloroplastic pigments (Chl-a and Pha-a) and TOC contents in relation to seasons and the northern Yellow Sea Cold Water Mass (NYSCWM). Decadal trends were also examined using linear regression on time-series data from 12 cruises conducted over a nine-year period (2006–2014). The correlations between sedimentary Chorophy-a (Chl-a), Pheophorbide-a (Pha-a), TOC, and their ratios with other abiotic and biotic factors were analyzed to detect any effects of the NYSCWM on the spatiotemporal distribution of sediment Chl-a, Pha-a, TOC contents, as well as the ecological relevance of their ratios as indicators of food quality (freshness) in the benthic system. The NYSCWM substantially influences the spatial and seasonal distribution of sedimentary Chl-a, Pha-a, and TOC contents. High values of Pha-a, TOC, and the ratios of Pha-a/(Chl-a + Pha-a) and TOC/Chl-a were often observed in the central region of the NYSCWM, where Chl-a showed clear seasonal fluctuations while Pha-a and TOC remained relatively constant. While sedimentary TOC appears to negatively mirror the spatial pattern of primary productivity in the water column, the spatial pattern of sedimentary Chl-a in relation to NYSCWM is less evident. However, the contents of Pha-a and TOC in the central NYSCWM sediments were higher than those at surrounding NYSCWM stations. Surface sediment Pha-a/(Chl-a + Pha-a) ratio was negatively correlated with meiofauna abundance and biomass and positively correlated with nematode/copepod ratio. This finding indicates that the quality of sediment organic matter is important to meiofauna. Conversely, the lower organic degradation rate at the lower bottom temperature of the NYSCWM may explain the observed higher Pha-a and TOC contents in its central area. Time-series data collected over nine years at the NYSCWM stations showed a decreasing trend for Chl-a, while TOC and the ratio of Pha-a/(Chl-a + Pha-a) exhibited increasing tendencies. This trend may imply a reduced quality of food supply to the benthic food web in the shelf sea system, along with degraded ecosystem functioning and service under the impacts of global change and anthropogenic disturbances.

Long-term carbon storage in shelf sea sediments reduced by intensive bottom trawling

AbstractBottom trawling represents the most widespread anthropogenic physical disturbance to seafloor sediments on continental shelves. While trawling-induced changes to benthic ecology have been widely recognized, the impacts on long-term organic carbon storage in marine sediments remains uncertain. Here we combined datasets of sediment and bottom trawling for a heavily trawled region, the North Sea, to explore their potential mutual dependency. A pattern emerges when comparing the surface sediment organic carbon-to-mud ratio with the trawling intensity represented by the multi-year averaged swept area ratio. The organic carbon-to-mud ratio exhibits a systematic response to trawling where the swept area ratio is larger than 1 yr−1. Three-dimensional physical–biogeochemical simulation results suggest that the observed pattern is attributed to the correlated dynamics of mud and organic carbon during transport and redeposition in response to trawling. Both gain and loss of sedimentary organic carbon may occur in weakly trawled areas, whereas a net reduction of sedimentary organic carbon is found in intensely trawled grounds. Cessation of trawling allows restoration of sedimentary carbon stock and benthic biomass, but their recovery occurs at different timescales. Our results point out a need for management of intensely trawled grounds to enhance the CO2 sequestration capacity in shelf seas.

Bottom–up propagation of synoptic wind intensification and relaxation in the planktonic ecosystem of the South Senegalese Upwelling Sector

ABSTRACT Synoptic intensification or relaxation of upwelling favorable winds are major sources of variability in eastern boundary upwelling systems. This study aims to investigate their impact on the planktonic ecosystem of the South Senegalese Upwelling Sector (SSUS), located south of the Cape Verde peninsula over a wide and shallow continental shelf. Numerical experiments using a three-dimensional coupled physical–biogeochemical model with four plankton functional types simulated the response of the coastal planktonic ecosystem to idealized synoptic (∼10 days) wind intensification and relaxation of the same amplitude. We find that these perturbations induce spatio-temporal oscillations of plankton concentrations. Zooplankton response occurred with a time lag that manifests itself in space as an equatorward/downstream shift in distribution relative to phytoplankton. Overall, the transmission of the synoptic perturbation from the physics to zooplankton is characterized by a damping in relative anomalies. All these elements and the weakness of the asymmetries in the biogeochemical/planktonic ecosystem responses between intensification and relaxation events support the hypothesis that synoptic variability has limited impact on the climatological state of low–latitude upwelling systems such as the SSUS. PLAIN LANGUAGE SUMMARY In some coastal regions of the world such as off Senegal, winds preferentially blow alongshore and induce subsurface, cold and nutrient rich waters to rise to the surface layer and favor the development of plankton blooms. These so-called upwelling favorable winds are not steady. Their fluctuations produce dynamical and biogeochemical variability over a broad range of scales. Here, we studied the biogeochemical effect of 10-day (i.e. weather or synoptic) wind fluctuations over the southern Senegal continental shelf. We used a numerical model with a simplified planktonic ecosystem consisting of two phytoplankton and two zooplankton size classes. The wind perturbations modulate ocean physics, the enrichment of the sun-lit surface layer in nutrients and the planktonic ecosystem. The plankton’s response to wind fluctuations exhibited oscillations more complex and relatively less intense than those of the wind. The modest effect of the studied short-term wind fluctuations on plankton found in this study may be specific to low-latitude coastal oceans with wide continental shelves.

Jurassic depocenters development, between Colorado basin, Chelforó sub-basin and Neuquén basin

Northern Patagonia, to the north of the Somún Cura Massif along the 39°S parallel, is characterized by the development of a series of Jurassic depocenters, initiating in the Andes to the west, across the Neuquén basin and the Pampean sector (Chelforó sub-basin) towards the Atlantic coast near the location of the Pedro Luro −1 well (onshore Colorado basin), and further east over the Argentine shelf, where multiple Jurassic depocenters form the Colorado, Rawson, and Valdés basins.Using marine and continental gravity data (Free air and Isostatic anomalies respectively), constrained by well and seismic data, an integrated interpretation workflow for the study area was carried out. The southern limit of the Neuquén Basin is controlled by the Huincul High, an E-W directed structure with a positive gravimetric anomaly, interpreted as a basement high limited by relative gravimetric lows to the north and south of the structure. The eastern sector includes a series of isolated depocenters, separated by basement highs (obliquely oriented) and limited to the south by the E-W anomaly of the Huincul High. These depocenters correspond to the Chelforó sub-basin, which was drilled in a recent exploration campaign obtaining Jurassic ages where seismic interpretation pointed out presumably Jurassic deposits. Between Valcheta and Sierra Grande, this positive anomaly turns NW and becomes the southern boundary of the Pedro Luro depocenter, partially drilled by the Pedro Luro- 1 well, with possibly Tithonian palynological records at total depth. Between the Pedro Luro depocenter and the Chelforó sub-basin some features consistent with basement highs with circular morphology have been identified on gravimetric data, located in the area limited between the Colorado and Río Negro rivers. Jurassic rift depocenters have also been interpreted further east, in the Colorado basin where depocenters are controlled by an E-W oriented basement high, and further east by NW trending structures near the position of the SDRs (seaward dipping reflectors on the continental-oceanic crust transition zone).The common evolution of these Jurassic depocenters is still poorly understood. They extend for more than 1500 km from the Andes to the Atlantic continental shelf and are controlled by structures located to the north of the Somún Cura Massif. The interpretation of seismic lines, and gravimetric data in areas without deep wells allow the identification of new exploration targets increasing the exploration potential of these basins.

Field Observations of Surfzone Vorticity

AbstractIn the surfzone, breaking‐wave generated eddies and vortices transport material along the coast and offshore to the continental shelf, providing a pathway from land to the ocean. Here, surfzone vorticity is investigated with unique field observations obtained during a wide range of wave and bathymetric conditions on an Atlantic Ocean beach. Small spatial‐scale [O(10 m)] vorticity estimated with a 5 m diameter ring of 14 current meters deployed in ∼2 m water depth increased as the directional spread of the wave field increased. Large spatial‐scale [O(100 m)] vorticity calculated from remote sensing estimates of currents across the surfzone along 200 m of the shoreline increased as alongshore bathymetric variability (channels, bars, bumps, holes) increased. For all bathymetric conditions, large‐scale vorticity in the inner surfzone was more energetic than in the outer surfzone.

Seafloor sediment characterization improves estimates of organic carbon standing stocks: an example from the Eastern Shore Islands, Nova Scotia, Canada

Abstract. Continental shelf sediments contain some of the largest stocks of organic carbon (OC) on Earth and play a vital role in influencing the global carbon cycle. Quantifying how much OC is stored in shelf sediments and determining its residence time is key to assessing how the ocean carbon cycle will be altered by climate change and possibly human activities. Spatial variations in terrestrial carbon stocks are well studied and mapped at high resolutions, but our knowledge of the distribution of marine OC in different seafloor settings is still very limited, particularly in dynamic and spatially variable shelf environments. This lack of knowledge reduces our ability to understand and predict how much and for how long the ocean sequesters CO2. In this study, we use high-resolution multibeam echosounder (MBES) data from the Eastern Shore Islands offshore Nova Scotia (Canada), combined with OC measurements from discrete samples, to assess the distribution of OC content in seafloor sediments. We derive four different spatial estimates of organic carbon stock: (i) OC density estimates scaled to the entire study region assuming a homogenous seafloor, (ii) interpolation of OC density estimates using empirical Bayesian kriging, (iii) OC density estimates scaled to areas of soft substrate estimated using a high-resolution classified substrate map, and (iv) empirical Bayesian regression kriging of OC density within areas of estimated soft sediment only. These four distinct spatial models yielded dramatically different estimates of standing stock of OC in our study area of 223 km2: 80 901, 58 406, 16 437 and 6475 t of OC, respectively. Our study demonstrates that high-resolution mapping is critically important for improved estimates of OC stocks on continental shelves and for the identification of carbon hotspots that need to be considered in seabed management and climate mitigation strategies.

Utilization of stable isotopes in teeth to investigate pygmy sperm whales (Kogia breviceps) in the southeastern United States

AbstractThe pygmy sperm whale (Kogia breviceps) is currently the second‐most stranded cetacean in the southeastern United States (SEUS), but information concerning their population structure is severely limited. This study used stable isotope analysis to investigate the isotopic niches and population structure of K. breviceps among three regions in the SEUS determined by the distance of the continental shelf break and a fourth region in the Gulf of Mexico. Teeth from stranded individuals were subsampled via dental drill at four separate areas on each tooth, representing four different age classes: calf, juvenile, subadult, and adult. Stable isotope ratios of carbon and nitrogen were measured in the organic component of 42 teeth, and oxygen isotope ratios were measured in the inorganic (hydroxyapatite) component of 19 teeth. No differences were found in δ13C, δ15N, or δ18O values between regions. However, differences between age classes were significant for adults and subadults for δ13C and adults and juveniles for δ15N. Differences between males and females were also significant for δ15N. Results from this study provide the first carbon and nitrogen isotope values from different age classes of pygmy sperm whales as well as the first reported oxygen isotope values for this species.

Geochemical characterization of trace fossil assemblages in spotted marls and limestones of the Lower Jurassic of the Western Carpathians: environmental implications

AbstractThe trace fossils of the spotted limestones and marls from upper Pliensbachian of the Skladaná Skala section, Western Carpathians (Slovakia), are characteristic of Zoophycos ichnofacies preserved in outer shelf deposits. The ichnoassociation is dominated by Lamellaeichnus and Chondrites, while Palaeophycus, Planolites, Teichichnus, Thalassinoides, Trichichnus, and Zoophycos, are less abundant. The presence of relatively large sized traces (reaching a decimetre in horizontal dimension for Thalassinoides and Zoophycos) and continuously well bioturbated deposits point to well oxygenated shallow zone (mixed layer) and deeper part of stiffed substrate of the transitional layer of bottom substrate up to the first tens of centimetres to depth. A first tier (tier I) corresponds to the shallowest sediment occupied by Bathysiphon tests and other epifaunal body fossils. The tier II is characterized by shallow infaunal burrows of deposit feeders (Planolites) and permanent dwelling, open burrows (Palaeophycus, Thalassinoides) located in a Ca-rich sediment (corresponding to CaCO3). The tier III is dominated by deposit feeders (Lamellaeichnus, Teichichnus) that burrowed stiff Ca-rich sediment below the redox boundary. Trace fossils of tier III are rich in fine siliciclastics (high content in Si, Al, K mainly associated to clays) and pyrite framboids (enrichment in Fe, S and Co). The deposit-feeders of tier III maintain connection to the sediment-water interface. Tier IV (Zoophycos, Teichichnus and large Chondrites), and deepest infaunal forms of the tier V. (Trichichnus, Pilichnus and tiny forms of Chondrites) comprises trace fossils commonly rich in pyrite framboids with relatively high content of Fe, S, and Co, congruent with chemosymbiotic behaviour commonly inferred for Chondrites, Trichichnus, and the organic-matter storage of Zoophycos.

Lithology and sedimentation conditions of the latest Cretaceous of the Klementyeva Mountain section (Eastern Crimea)

Overall study of the boundary Maastrichtian–Danian deposits of Klementyeva Mountain section (Eastern Crimea) was carried out. The lithological characteristics of carbonate, carbonate-argillaceous and clastic rocks were described in detail, the dynamic of changes in foraminifera assemblages was analyzed. For the first time, geochemical and isotopic data were obtained for this section. The stratigraphic complement of the Upper Maastrichtian and Lower Danian has been specified. Late Campanian – Early Maastrichtian age of the underlying deposits was established, for the first time. The Klementyevskaya Formation was formed in deep-sea pelagic paleoenvironments on the submerged part of the outer shelf, and the overlying Lower Danian sediments were formed in shallow waters of the inner shelf with terrigenous sedimentation and high hydrodynamic activity.

Zinc isotope perspective on global carbon cycling during the onset of the late Paleozoic icehouse

The onset of the late Paleozoic icehouse coincided with a large global carbon-cycle perturbation (represented by the mid-Tournaisian carbon isotope excursion [TICE]), although the underlying cause of this isotopic event remains uncertain. Zinc (Zn), an essential micronutrient for plankton, has an isotopic composition (δ66Zn) in seawater that is sensitive to subtle fluctuations in marine carbon (C) cycling. Here, we investigated C cycling during the TICE using paired carbonate δ66Zn-δ13C and organic δ13C records from two widely spaced sections in South China. These records reveal coupling between δ66Zn and δ13C over an ∼4 m.y. interval in the form of two positive excursions (Peaks I and II) separated by a negative shift (interpeak). Peak I is attributed to enhanced marine primary productivity (MPP), which was stimulated by increased micronutrient supply linked to enhanced silicate weathering and/or upwelling. The interpeak may record oxidation of remobilized organic matter from continental shelves exposed by glacio-eustatic sea-level fall, which, in turn, promoted MPP again and resulted in Peak II. Thus, the TICE records complex climate−carbon cycle feedbacks that may have led to large-scale organic carbon burial and driven stepwise cooling, marking the onset of a sustained late Paleozoic icehouse climate.

Otolith growth chronologies reveal distinct environmental sensitivities between and within shallow- and deep-water snappers

AbstractFish growth underpins individual fitness and population-level metrics, with fluctuations linked to environmental variability. Growth chronologies derived from otolith increment analysis are a powerful proxy to understand population responses to environmental change and productivity. Yet, long-term patterns of growth and their environmental drivers are better understood for shallow-water species compared to deep-water inhabitants. Additionally, focus is largely on adults, disregarding the potential influence of juvenile growth which is critical to size- and age-at-maturity. Here, we investigate the long-term growth patterns of two commercially important snapper species separated by depth in northwestern Australia’s coastal shelf waters, the shallow-water Lutjanus sebae (70 year chronology, 1950–2020) and the deep-water Etelis boweni (41 year chronology, 1973–2013). Annually-resolved otolith growth chronologies revealed distinct environmental sensitivities within (juveniles vs adults) and among (shallow- vs deep-water habitats) species. Within species, juveniles and adults responded differently to shared environmental stimuli, highlighting the importance of understanding the impacts of environmental effects and sensitivities for different life-history stages. Across species, L. sebae exhibited highly variable growth tied to local climate signals such as sea surface temperature and rainfall, while E. boweni displayed more stable growth patterns that only responded to interannual and decadal shifts in the environment (e.g. Pacific Decadal Oscillation). Our results highlight potential vulnerabilities of shallow-water species to future environmental perturbations compared to species residing at depth, as they are likely to encounter more extreme climate variability under future oceanic conditions. This study contributes valuable insights into understanding and managing the impacts of future environmental variability on fisheries sustainability, emphasising the need for continued research across species and habitats.