Search

The Canary Current Large Marine Ecosystem (CCLME) is one of the most productive Large Marine Ecosystems worldwide. Assessing the abundance, biomass and distribution of zooplankton in the southern part of this system, off the coast of West Africa, remains challenging due to limited sampling efforts and data availability. However, zooplankton is of primary importance for pelagic ecosystem functioning. We applied an inversion method with combined analysis of acoustic and biological data for copepod discrimination using a bi-frequency (38 and 120 kHz) approach. Large copepods with equivalent spherical radii > 0.5 mm were identified using differences in the mean volume backscattering strength (MVBS). Regarding abundance measured by net sampling, copepods strongly dominated the zooplankton community and the large fraction account for 18%. This estimate correlated significantly with MVBS values that were obtained using an inverse algorithm. We confirmed the utility of using 38 kHz for large copepod detection. An epipelagic biomass of large copepod was estimated at 120–850 mg m-2 in March during upwelling season. It is worth noting that this estimation likely underestimates the true biomass due to inherent uncertainties associated with the measurement method. We recommend future investigations in the interest of using only nighttime data to improve the sampling pattern, particularly on the upper part of the water column (< 10 m) as well as on the shallow part of the continental shelf (< 20 m depth) not covered by fisheries vessel. Nevertheless, such high copepod biomass supports high fish production underlining the key role of copepod in the CCLME. Our results open the way to the analysis of the fluctuation and trend of copepod biomass, along with three decades of fisheries acoustics data available in the region. This helps to determine ecosystem changes, particularly under climate change, and to investigate the role of copepods in the southern CCLME carbon pump at the fine scale. [ABSTRACT FROM AUTHOR]

The solution from linear theory for the barotropic-to-baroclinic tidal energy conversion into vertical modes is validated with numerical simulations and analytical results. The main result is the translation of the traditional critical slope condition into a modewise condition on the topographic height only. Our findings are then used for estimates of the global M2 tidal conversion into the first 10 vertical modes in the open ocean (excluding the continental shelves and slopes). We observe a rapid increase with mode number of the fraction of the World Ocean where linear theory is invalid. In terms of conversion, which is highly variable in space, this corresponds to an even more rapid increase with mode number of the fraction of the converted energy that is strongly affected by nonlinear effects. Out of the 373.6 GW of the globally integrated conversion into modes 1–10, only 241.7 GW occur in locations where linear theory is valid. While it represents 95% for mode 1, this fraction rapidly drops with mode number to reach 27% for mode 10. Moreover, for the conversion into a single mode, we show that capping the linear solution at supercritical topography is inappropriate. Hence, linear theory appears unfit to directly quantify the role played by high-mode internal tides in the internal wave energy budget. [ABSTRACT FROM AUTHOR]

The jurisprudence concerning the continental shelf delimitation beyond 200 nautical miles (nm) over the past decade converged on distinguishing delineation from delimitation, which justifies the appropriateness of the judiciary to delimit the continental shelf beyond 200 nm in the absence of the recommendations issued by the Commission on the Limits of the Continental Shelf (CLCS). Mauritius/Maldives decided by a special chamber of the International Tribunal for the Law of the Sea departs from the established jurisprudence. By applying a 'significant uncertainty' standard that puts the relationship between entitlement and delimitation in the centre, Mauritius/Maldives reasons against exercising jurisdiction over the delimitation beyond 200 nm without affirmative recommendations of the CLCS. Mauritius/Maldives reflects judicial restraint in contrast with a more proactive approach prevailing in previous jurisprudence. [ABSTRACT FROM AUTHOR]

The Antarctic benthos is rich in biodiversity, with many species being endemic to the Southern Ocean. Multiple factors such as oceanic currents, glacial cycles and reproductive life stages have been attributed to the distribution of benthic dwelling invertebrates around the continent. The sea spider (Pycnogonida) Nymphon australe is a paternal brooder, which lacks a pelagic planktonic life stage. Typically brooding is assumed to suggest limited dispersal capabilities. Here we investigated the genetic structure of N. australe, a highly abundant pycnogonid species in the Southern Ocean to test assumptions of a documented circumpolar distribution. Previous studies with mitochondrial data have revealed that N. australe has high genetic diversity, limited gene flow, as well as distinct geographic structure. To resolve the phylogeographic structure of the circumpolar N. australe from the Antarctic continental shelf, we used 3RAD single nucleotide polymorphism (SNP) data from 111 individuals sampled from ten different, circumpolar geographic regions including the Western Antarctic Peninsula, Ross Sea, Weddell Sea, and Eastern Antarctica. Analyses revealed populations to have distinct regional populations with strong geographic structuring observed by locality and suggest the possibility that N. australe may be a species complex in the Southern Ocean. [ABSTRACT FROM AUTHOR]

New biostratigraphically constrained chronologies have been developed to help elucidate the sedimentary and tectonic history of Quaternary sequences on the Hikurangi margin of north-eastern Zealandia. Three sites on the mid to lower slope of the accretionary prism (IODP Site 372-U1517, 375-U1519, 375-U1518) and two sites east of the deformation front (Hikurangi Trough Site 375-U1520 and Tūranganui Seamount Site 375-U1526) are dated using a detailed biostratigraphic framework based on planktic foraminiferal records from ODP Site 181-1123. The dating indicates sedimentation rates are very high and variable on the accretionary prism (0.2–9.6 m/kyr), especially during the Last Glacial Maximum (LGM) when downslope redeposition from the continental shelf and upper slope is common. Sedimentation rates at Hikurangi Trough Site 375-U1520 are also variable (0.01–3.0 m/kyr) and they increase markedly as the incoming site approached the deformation front, especially during the LGM, due to an abundance of downslope redeposition from the inner to mid shelf. The incoming Quaternary section at Tūranganui Seamount Site 375-U1526, is punctuated by hiatuses that shorten in duration as the site approached the deformation front, whilst sedimentation rates remain relatively low (0.04–0.4 m/kyr). [ABSTRACT FROM AUTHOR]

Across the world's oceans, our knowledge of the habitats on the seabed is limited. Increasingly, video/imagery data from remotely operated underwater vehicles (ROVs) and towed and drop cameras, deployed from vessels, are providing critical new information to map unexplored benthic (seabed) habitats. However, these vessel-based surveys involve considerable time and personnel, are costly, require favorable weather conditions, and are difficult to conduct in remote, offshore, and deep marine habitats, which makes mapping and surveying large areas of the benthos challenging. In this study, we present a novel and efficient method for mapping diverse benthic habitats on the continental shelf, using animal-borne video and movement data from a benthic predator, the Australian sea lion (Neophoca cinerea). Six benthic habitats (between 5-110m depth) were identified from data collected by eight Australian sea lions from two colonies in South Australia. These habitats were macroalgae reef, macroalgae meadow, bare sand, sponge/sand, invertebrate reef and invertebrate boulder habitats. Percent cover of benthic habitats differed on the foraging paths of sea lions from both colonies. The distributions of these benthic habitats were combined with oceanographic data to build Random Forest models for predicting benthic habitats on the continental shelf. Random forest models performed well (validated models had a >98% accuracy), predicting large areas of macroalgae reef, bare sand, sponge/sand and invertebrate reef habitats on the continental shelf in southern Australia. Modelling of benthic habitats from animal-borne video data provides an effective approach for mapping extensive areas of the continental shelf. These data provide valuable new information on the seabed and complement traditional methods of mapping and surveying benthic habitats. Better understanding and preserving these habitats is crucial, amid increasing human impacts on benthic environments around the world. [ABSTRACT FROM AUTHOR]

The southeastern Australian margin hosts a series of submarine canyons. Although the origin and evolution of canyons within the northwestern segment of the margin is relatively well studied, their quantitative morphology, interaction with longshore drift currents and slope failure remain poorly understood in the southeastern region. In this study, high-resolution bathymetry and 3D seismic reflection datasets revealed five main submarine canyons present in the central offshore Otway Basin. The canyons have V-shaped, evolving to U-shaped morphology downslope with sedimentary infill characterized by medium–high amplitudes, recognizable stratal pattern and localized chaotic seismic reflections. Analysis reveals these canyons were initiated by retrogressive slope failure on the continental slope, that once the shelf edge was reached and subsequently incised, development of the canyon heads was influenced by the shelf parallel Zeehan Current, active on the continental shelf of the region. The heads of the shelf-incised canyons preferentially migrate northwestward and were infilled by laterally accreting sedimentary packages characterized by southeast dipping seismic reflections. These indicate an early erosive phase followed by a period of deposition, a result of the prevalent eastward flowing Zeehan Current. These results have important implications for understanding of the mechanisms that control initiation and development of submarine canyons, and their morphology, both offshore southeastern Australia, and similar settings on continental margins worldwide. [ABSTRACT FROM AUTHOR]

A study on Holocene ostracods (subfamilies Cytherurinae and Paracytherideinae) was carried out in 500 bottom sediments samples recovered along the Brazilian continental shelf from Rio Grande do Sul (33º45’S/52ºW) to Espírito Santo (19º35’S/40ºW) states. New species belonging to the subfamily Cytherurinae are here identifi ed and described as follows: Eucytherura rara sp. nov., E. trifi da sp. nov., E. castellata sp. nov., and Semicytherura reticulocostata sp. nov. Three other species are kept in open nomenclature due to scarcity of material for study: Semicytherura sp. 1, Semicytherura sp. 2 and Hemingwayella sp., the last one representing the subfamily Paracytherideinae. The zoogeographical and stratigraphical analyses revealed that most of the species identifi ed do not exceed the latitude 19º30.1’S with the southernmost record at 33º52’S; some of these species extending to the Uruguayan and Argentinian shelves. Exceptions are the species Semicytherura parallelocostata and Semicytherura sp. 2 that reach the northeast and equatorial Brazilian continental shelves at latitudes 10º32’S and 00º08’S, respectively. Two of the studied species have a fossil record in the Pelotas Basin (Brazil): Hemicytherura auriculata (Miocene and Pleistocene) and Semicytherura rugosoreticulata (Holocene). Hemicytherura lapillata has been recorded in a Holocene outcrop in Bahia Blanca (Argentina). [ABSTRACT FROM AUTHOR]

The concentrations and composition of hydrocarbons (aliphatic, AHCs, and polycyclic aromatic, PAHs) are determined using molecular markers in bottom sediments of the Greenland–Norwegian basin and the Barents Sea (during the 84th cruise of the R/V Akademik Mstislav Keldysh in 2021). The research covered the deep-sea part of the Greenland Basin, the northern part of the East Greenland Ridge, the near-fault zone in the area of the junction of the Mohns and Knipovich ridges, the Western and Northwestern extremities of the Svalbard continental shelf (the Vestnes Ridge, the Ermak Plateau, the Sofia Basin, and the Hinlopen Trough), the Fram Strait, the Orly trough area with the intersection of the Erik-Eriksen trough, and the central part of the Barents Sea. The surface bottom sediments are found to contain a wide range of concentrations of Corg (0.25%–2.71%), AHCs (7–182 μg/g), and PAHs (23–1918 ng/g). The distribution of HCs is determined by the processes occurring in the sedimentary stratum (changes in Eh and fluid flows), and, to a lesser extent, by the lithotype of sediments. Therefore, in the sedimentary stratum, autochthonous components form in the composition of alkanes and naphthalenes form in the composition of PAHs. [ABSTRACT FROM AUTHOR]

In winter, the Kuroshio Current intrudes onto the continental shelf in the East China Sea with a cyclonic branch occasionally veering northeast of the Taiwan Strait. The dynamic process and mechanism by which the southward Kuroshio branch enters the Taiwan Strait is investigated using a numerical model. Decomposition of the flow field and sea surface height (SSH) using the empirical orthogonal function (EOF) isolates the first mode of the southward flow and the east‐westward SSH slope, showing that the time series is closely related to wind strength. The southward Kuroshio branch is mainly controlled by geostrophic and Ekman effects. When northeasterly winds are weak, the elevated SSH on the eastern side, caused by the Kuroshio, generates a northward geostrophic current. This northward current overwhelms the Ekman current and triggers the Taiwan Warm Current. Conversely, when northeasterly winds are strong, an elevated SSH on the western side generates a southward geostrophic current. A theoretical equation is devised, which accounts for Ekman layer depth related to wind strength and geostrophic adjustments by the Ekman effect. This equation explains why the Kuroshio branch flows into the northern Taiwan Strait and why there is a counter‐wind current (i.e., Taiwan Warm Current) during winter. Furthermore, we propose a novel perspective that suggests the alongshore current and cross‐shore sea level in the Taiwan Strait are determined by the wind‐driven current and geostrophic adjustment, which are generated by the competition or cooperation between the wind and the alongshore pressure gradient caused by the Kuroshio. [ABSTRACT FROM AUTHOR]

Estuaries are one of the most productive ecosystems in the world, supporting a variety of flora and fauna. Primary productivity by phytoplankton is a rich source of organic carbon, substantial for the aquatic food web. Monitoring phytoplankton (i.e., chlorophyll-a) is essential to assess the health of estuaries and other continental shelves subjected to constant anthropogenic stress (e.g., developmental activities). In this study, a three-endmember combination Spectral Decomposition Algorithm (SDA) was developed to estimate the phytoplankton in the micro-tidal Yura estuary of Japan using Landsat-8 (30 m), and Sentinel − 2A (10 m). The endmember water, phytoplankton, and submerged aquatic vegetation (SAV) yielded the best results with both the satellite sensors (R2 > 0.80) owing to the limited influence of non-phytoplankton suspended solids (NPSS) in the estuary. Chlorophyll-a was used as the proxy for phytoplankton. The estimated root mean square error (RMSE) was relatively higher in Landsat-8 (RMSE = 0.187 µg/L) than the Sentinel-2A (RMSE = 0.162 µg/L). The results were validated using the ground truth data of the Yura Estuary (26 sampling points). Furthermore, the results indicate low chlorophyll-a concentration in the Yura estuary (< 2µg/L) except near the shorelines (~ 6 µg/L). A good fit (R2 = 0.79) between observed chlorophyll-a and turbidity indicated phytoplankton-dominated turbidity in the tide-less estuary of Japan. The estimated maximum turbidity was 1.4 FTU using both sensors, suggesting a low anthropogenic influence on the Yura Estuary. The study demonstrates a successful application of the spectral decomposition algorithm (SDA) in the coastal waters which could further be used to assess the horizontal and temporal variability in phytoplankton in estuarine water. [ABSTRACT FROM AUTHOR]

Man-made structures in the marine environment such as offshore Oil & Gas infrastructure are known to provide a hard substrate that enables ecosystems to develop on and around them. Current decommissioning practices on the UK Continental Shelf are mandated by the OSPAR Decision 98/3 with the premise of a clean seabed at its core, meaning that it is the expectation that all infrastructure is completely removed at the end of its operation life, leaving a clear seabed behind. This study critically reviewed 49 peer-reviewed articles relating to the ecosystem and the impact to these ecosystems by current removal practices. The results clearly demonstrate that current science-based evidence shows that existing O&G platform substructures act as multipurpose artificial reefs upon which rich ecosystems have developed and that their removal degrades the overall North Sea marine environment. Furthermore, this study shows that clearsea bed policies, such as OSPAR 98/3, do not reflect, nor understand the complex relationship and interdependencies between biology and man-made structures and do not reflect current scientific knowledge. It is concluded that based on current knowledge, it is no longer scientifically justifiable to mandate the removal of all O&G infrastructure during decommissioning and that applying the principle of a clean seabed according to the OSPAR Commission should be re-considered. [ABSTRACT FROM AUTHOR]

This study investigates the biogeochemical drivers of aragonite saturation state (ΩAr) in Baffin Bay, with a focus on the relatively undersampled west Greenland shelf. Our findings reveal two main depth‐dependant processes controlling the spatial distribution of ΩAr in Baffin Bay; within the upper 200 m, lower ΩAr coincides with increasing fractions of Arctic‐outflow waters, while below 200 m organic matter respiration decreases ΩAr. A temporal analysis comparing historical measurements from 1997 and 2004 with our 2019 data set reveals a significant decrease in the ΩAr of Arctic‐outflow waters, coinciding with reduced total alkalinity (TA). However, no discernible anthropogenic ocean acidification signal is identified. Significant Arctic water fractions (20%–40%) are found to be present on the west Greenland shelf, associated with reduced TA and ΩAr. A numerical modeling simulation incorporating a passive tracer demonstrates that periodic changes in wind direction lead to a switch from onshore to offshore Ekman transport along the Baffin Island current, transporting Arctic waters toward the west Greenland shelf. This challenges the conventional understanding of Baffin Bay's circulation and underscores the need for further research on the region's physical oceanography. Based on salinity‐TA relationships, surface waters on the west Greenland shelf have a significantly lower meteoric TA end‐member compared to waters of the Baffin Island Current in western Baffin Bay. The low eastern TA freshwater end‐member agrees well with recent glacial meltwater TA measurements, suggesting that glacial meltwater is the main freshwater source to surface waters on the west Greenland shelf. Plain Language Summary: Baffin Bay, with its complex interplay of Atlantic and Arctic water masses, is particularly susceptible to ongoing ocean acidification, mainly due to the presence of relatively fresh and low‐alkalinity Arctic waters. To date measurements of the inorganic carbon system in Baffin Bay have primarily been captured at key entrance and exit gateways, and on the Canadian side of the bay, leaving the west Greenland shelf relatively undersampled. This study provides a bay‐wide perspective of the main factors influencing aragonite saturation state (ΩAr; an indicator of ocean acidification impacts on marine calcifying organisms) across Baffin Bay, including the west Greenland shelf. We found that within the upper 200 m, low ΩAr coincides with increased presence of Arctic waters, while below 200 m the breakdown of organic matter decreases ΩAr. Historical data from 1997 and 2004 compared to our 2019 measurements show a significant drop in ΩAr of Arctic waters, but no clear signal of anthropogenic ocean acidification was observed. Surprisingly, the west Greenland shelf has significant fractions (20%–40%) of Arctic water. A numerical modeling simulation suggests that periodic changes in wind direction can transport Arctic waters from across Baffin Bay, challenging our traditional understanding of the bay's circulation. Key Points: Increased fractions of Arctic waters decrease aragonite saturation state (ΩAr) in the upper 200 m, while respiration does so below 200 mDecreased ΩAr of Arctic waters over the last two decades is associated with decreased alkalinity, not additional CO2Significant fractions of Arctic‐outflow waters on the west Greenland shelf challenges current knowledge of circulation in Baffin Bay [ABSTRACT FROM AUTHOR]

The East China Sea (ECS) is among the most important and highly dynamic shelf seas, where the coupling of physical and biogeochemical processes is distinctive and may play a crucial role in regulating nutrient conditions and the pattern of primary production. Based on field observations during the late summer of 2019, the physical controls of nutrient supply and the subsequent influences on phytoplankton chlorophyll‐a (Chl‐a) regime were investigated in the ECS. The coastal upwelling originating from the Kuroshio Subsurface Water (KSSW) intrusion serves as a nutrient source on the inner East China Sea (ECS) shelf, and this inshore upwelling combined with the coastal water largely governs the surface Chl‐a patterns. The halocline, thermocline and nutricline exhibit a vertically synchronous fluctuating phenomenon, and the coexistence of several subsurface cold rings/patches was significantly observed on the middle‐outer ECS shelf, indicating intense vertical advection and the occurrence of upwelling. The subsurface cold rings greatly regulate the vertical hydrodynamics, constituting unique upward pathways of the onshore intruded KSSW on the middle‐outer shelf. Nutrients can be upwelled within these cold rings to support primary production, thus partially leading to the spatial variability of subsurface Chl‐a maximum in terms of intensity and depth. Our findings would considerably contribute to our understanding of the physical‐biogeochemical‐ecological processes on the ECS shelf. Plain Language Summary: The East China Sea (ECS) is one of the most important continental shelves in the world. Exploring the physical‐biogeochemical processes is of great significance for the in‐depth understanding of ecosystem in this shelf sea. Here, specific attention was paid to the physical controls on the nutrient supply and the associated influences on phytoplankton chlorophyll‐a (Chl‐a) regime in the ECS. We show that the coastal/inshore upwelling originating from the nearshore branch of the Kuroshio Subsurface Water (KSSW) intrusion serves as a nutrient source on the inner ECS shelf. The co‐occurrence of several subsurface cold rings clearly indicates the upward transport of the onshore intruded KSSW on the middle‐outer ECS shelf. The subsurface cold rings may play a role in modulating the vertical hydrodynamics and related biogeochemical‐ecological processes, leading to the upward delivery of nutrients and enhanced Chl‐a levels. Our results would provide a sound scientific basis for the studies of biogeochemical and ecological dynamics in the ECS. Key Points: The coexistence of several subsurface cold rings indicating upwelling on the middle‐outer East China Sea shelf was observedSubsurface cold rings and coastal upwelling constituted unique upward pathways of the onshore intruded Kuroshio Subsurface WaterNutrients could be upwelled within the cold rings and potentially modulated the associated biogeochemical‐ecological processes [ABSTRACT FROM AUTHOR]

The Chukchi Borderland, connecting the Chukchi continental shelf and the Canada Basin, has become a hotspot for studying how ecosystems respond to rapid environmental changes in the Arctic Ocean. Based on a long‐term hindcast simulation during 1998–2015 using a coupled ocean‐sea ice‐biogeochemical model, this study investigates the responses of phytoplankton assemblage and the biological carbon pump efficiency within the upper layers (0–100 m) of the Chukchi Borderland. The nitrate concentration is found to be a crucial factor controlling the total phytoplankton biomass and determining the spatiotemporal variations in the evolution pattern of phytoplankton assemblage. In the shelf break adjacent region, nitrate concentration increased after 2009, boosting phytoplankton biomass with diatoms persistently dominating. In the Canada Basin adjacent region, the westward expansion of the Beaufort Gyre after 2009 extended the influence of oligotrophic water, leading to phytoplankton miniaturization and a shift in phytoplankton assemblage evolution, from a pre‐2009 pattern that non‐diatoms at start were succeeded by diatoms, to a post‐2009 scenario that non‐diatoms dominated throughout the growing season. The biological pump efficiency evidently increased in the shelf break region after 2009, due to heightened biomass and intensified horizontal advection‐induced particulate organic carbon (POC) supply. The western Canada Basin adjacent region presented the reduced primary production and vertical POC flux. However, the deeper nitracline deepened the phytoplankton habitat, shortening POC residence time in the upper layers and enhancing the biological pump efficiency. Plain Language Summary: The responses of marine phytoplankton and the biological carbon pump efficiency to rapid changes in the Chukchi Borderland are studied through analyzing a numerical model simulation spanning 1998–2015. In the upper ocean (0–100 m depth), the nitrate concentration is found to be a crucial factor for space‐time variations of the total biomass and the dominance of phytoplankton groups. Over the continental shelf and shelf break, nitrate increased after 2009, promoting the growth of larger‐size phytoplankton (diatoms) and sustaining their dominance throughout most of the growing season. In the region near western Canada Basin, the westward expansion of the Beaufort Gyre (nitrate‐low water) favored the smaller‐size phytoplankton growth. This shift is expected to reduce the quality of ecosystem production. The biological carbon pump efficiency generally increased after 2009, indicating a faster transfer of biologically fixed carbon into deep water. In the shelf break region, this efficiency increase was due to heightened local primary production and increased horizontal transport of particulate organic carbon supply. Near the western Canada Basin, it was due to a deeper phytoplankton habitat. These results provide new perspectives for the evaluation of carbon sinks in the western Arctic Ocean. Key Points: Nitrate levels shape regional differences in annual evolution of phytoplankton assemblageOligotrophic Canada Basin water leads to phytoplankton miniaturization and assemblage evolution shifts in its expanded regionBio‐pump efficiency is promoted by increased productivity and advected particulate organic carbon over shelf break, while by deeper habitat near Canada Basin [ABSTRACT FROM AUTHOR]

South‐west Australia has been identified as a global hotspot for the occurrence of meteotsunamis. In this study, a numerical hydrodynamic model (Regional Ocean Modelling System) was configured to investigate the generation of meteotsunamis through propagating thunderstorms. A range of simulations were performed using realistic and synthetic atmospheric forcing to establish the sensitivity of meteotsunami wave heights and waveforms along different parts of the coast to variations in the propagation speed and bandwidths of propagating pressure jumps associated with the thunderstorms. When a pressure jump propagated from the north and north‐west quadrants with a speed (U) of 8–15 ms−1, both the Proudman and Greenspan resonances were possible mechanisms for the generation of meteotsunamis. However, the response changed for different bandwidths of the propagating pressure jump and resulted in different meteotsunami waveforms at the coast. When U > 15 ms−1, long waves were amplified initially through shoaling at the shelf slope, with Proudman resonance enhancing the wave heights at corresponding resonant depths on the shelf, and then propagated as free waves on the continental shelf. The waves were further amplified at the coast through refraction and shoaling effects and resulted in an elevation wave at the coast. Numerical simulations also indicated that edge waves can also be excited near the coast when the incoming free wave wavelengths were equal to or half the edge wave wavelength. The study provides observational and numerical evidence to suggest that the bandwidth of propagating air pressure jumps plays a major role in meteotsunami generation and their waveforms. Plain Language Summary: The numerical simulation results show that meteotsunamis on the southwest Australian coast can be generated over a range of traveling pressure jump speeds and bandwidths, where Proudman resonance, Greenspan edge wave, refraction, and shoaling were responsible for the initial wave amplification. The simulations also revealed that resonance and shoaling amplification were determined by both the speed and bandwidth of the propagating pressure jumps. The pressure jump with constant translational speed can cause significantly different wave heights and waveform meteotsunami when the bandwidths were different. As the wave propagates southward with speeds of 15–28 ms−1, it undergoes subcritical, critical, and supercritical states over the shelf. The findings of this study provide preliminary guidelines for forecasting meteotsunamis generated by summer thunderstorms along the south‐west Australian coastline. Key Points: A range of moving atmospheric pressure jump speeds were conducive to meteotsunami generation on the southwest Australian coastProudman resonance, Greenspan edge waves, refraction, and shoaling were responsible for the generation and amplification of meteotsunamisThe resonance and shoaling amplification were influenced by both the speed of propagation and the bandwidths of the pressure jumps [ABSTRACT FROM AUTHOR]

A 25‐year (1996–2020) hindcast from a coupled physical‐biogeochemical model is evaluated with nutrients, phytoplankton and zooplankton field data and is analyzed to identify mechanisms controlling seasonal and interannual variability of the northern Gulf of Alaska (NGA) planktonic food web. Characterized by a mosaic of processes, the NGA is a biologically complex and productive marine ecosystem. Empirical Orthogonal Function (EOF) analysis combining abiotic and biotic variables averaged over the continental shelf reveals that light intensity is a main driver for nanophytoplankton variability during spring, and that nitrate availability is a main driver for diatoms during spring and for both phytoplankton during summer. Zooplankton variability is a combination of carry‐over effects from the previous year and bottom‐up controls from the current year, with copepods and euphausiids responding to diatoms and microzooplankton responding to nanophytoplankton. The results also demonstrate the effect of nitrate availability and phytoplankton community structure on changes in biomass and energy transfers across the planktonic food web over the entire growing season. In particular, the biomass of large copepods and euphausiids increases more significantly during years of higher relative diatom abundance, as opposed to years with higher nitrate availability. Large microzooplankton was identified as the planktonic group most sensitive to perturbations, presumably due to its central position in the food web. By quantifying the combined variability of several key planktonic functional groups over a 25‐year period, this work lays the foundation for an improved understanding of the long‐term impacts of climate change on the NGA shelf. Plain Language Summary: The northern Gulf of Alaska planktonic food web supports a highly productive and diverse marine ecosystem. Here we used a 25‐year model simulation (1996–2020) to explore how its structure and variability (from phytoplankton to krill) are affected by the highly variable environmental conditions experienced over the continental shelf each season and across years. A statistical analysis identifies light intensity as a main driver for small phytoplankton variability during spring, and nutrient availability as a main driver for large phytoplankton (diatoms) during spring and for both phytoplankton types during summer. Changes in zooplankton are influenced by abundances from the previous year and prey availability from the current year. In general, larger zooplankton species (copepods and krill) respond to large phytoplankton availability and smaller zooplankton species respond to small phytoplankton availability. Finally, the biomass of large zooplankton increases more significantly during years when large phytoplankton is relatively more abundant, as opposed to years when more nutrients are available. By advancing knowledge about the seasonal and year‐to‐year response of several key planktonic functional groups over the recent historical period (1996–2020), this work lays the foundation for an improved understanding of the long‐term impacts of climate change in the northern Gulf of Alaska region. Key Points: Drivers of recent seasonal and interannual variability of the Gulf of Alaska planktonic food web are explored with a 25‐year hindcastLight and nutrient availability are the main drivers of phytoplankton production, but their effect varies by season and functional groupTrophic energy transfer to larger zooplankton is more sensitive to changes in phytoplankton composition than to changes in abundance alone [ABSTRACT FROM AUTHOR]

Numerical predictions of nearshore waves and shoreline runup are usually initialized on the inner shelf, seaward of the surfzone, with sea‐swell (SS) waves from local wave buoys or regional wave models. Lower frequency infragravity (IG) waves are not reliably measured by buoys or included in regional models. Here, co‐located pressure and velocity observations are used to characterize IG waves in 10–15 m depth in southern California. Shoreward propagating IG waves are often dominated by free waves, with the boundwave energy fraction <30% for moderate and low energy incident SS waves. Only 5% of records, with energetic long swell, show primarily bound waves. The shoreline slope of concave beaches increases by ∼3 between spring high and low tides, and free seaward and shoreward IG energy in 10–15 m vary tidally. The observed linear dependency of free IG energy on SS energy and period is consistent with Ardhuin et al. (2014, https://doi.org/10.1016/j.ocemod.2014.02.006)'s parameterization (R2 = 0.71). Including the tide level as a proxy for beach slope and modifying the SS frequency dependency increases R2 to 0.91. The ratio of free seaward to shoreward propagating IG energy suggests between 50 and 100% of the energy radiated seaward in depths of 10–15 m is trapped offshore and redirected shoreward. Free (random phase) and bound (phase‐coupled) IG waves are combined to initialize the SWASH numerical model. SWASH predicted runup is only weakly influenced by waves at the offshore boundary. Nonlinear IG generation and dissipation in the shoaling and surfzone overwhelm the effects of shoreward propagating waves observed at the offshore boundary. Plain Language Summary: Infragravity (IG) waves are long‐period (25 s–2.5 min) waves that contribute to coastal flooding and beach erosion. IG waves, generated near the shoreline by short‐period sea‐swell (SS) wave groups (known by surfers as "sets"), have long wavelengths (100s of m) and do not typically curl and break like ordinary sea and swell waves. Instead, they can be reflected off the beach face and propagate seaward. Our study concerns IG waves on the inner shelf (10–15 m depth, ∼500–700 m offshore), seaward of the main region of IG generation. Similar to previous observations in Hawai'i and North Carolina, we find most of the reflected, seaward‐going IG energy cannot reach deep water and is trapped on the continental shelf. We develop an observation‐based estimate of IG wave energy on the inner shelf as a function of SS wave energy and tide level. Finally, we show with a numerical model that IG wave runup at the shoreline is influenced only weakly by IG waves on the inner shelf. Key Points: Infragravity (IG) waves on the inner shelf (10–15 m depth) in San Diego, USA are often dominated by refractively trapped free wavesFree IG energies are parameterized as a function of local sea‐swell conditions and tide levelNumerically modeled wave runup is only weakly influenced by the shoreward propagating IG waves observed at the offshore boundary [ABSTRACT FROM AUTHOR]

Six Antarctic toothfish (Dissostichusmawsoni) have been analyzed for qualitative and quantitative determination of muscular lipid distribution. The specimens were representative of different physical condition and life stage: two adults in good condition and two adults in poor condition (termed "axe handles" based on their emaciated shape) from the spawning area of the Ross Sea seamounts, and two sub-adults from the continental shelf. Axe handles had lower lipid quantities. Among the individuals in good condition, adults from the seamounts had higher accumulation of lipid in the dorsal portion, maybe related to the neutral buoyancy for the reproductive migration. Thirteen saturated fatty acids (SFA) and three unsaturated fatty acids (UFA) have been identified. Subadults from the shelf had higher SFA/UFA ratios in the anterior part of the body, where they might store somatic lipids for buoyancy. The individuals from the spawning area had higher SFA/UFA ratios in the posterior part of the trunk, indicating after the migration a primary consumption of the somatic fatty acids near the center of buoyancy. SFA uptake from the diet seems to be difficult at the spawning area and they may be replaced by UFA. This translates into a reduced ability to re-acquire neutral buoyancy for a returning migration. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Siberian Arctic is warming rapidly, causing permafrost to thaw and altering the biogeochemistry of aquatic environments, with cascading effects on the coastal and shelf ecosystems of the Arctic Ocean. The Lena River, one of the largest Arctic rivers, drains a catchment dominated by permafrost. Baseline discharge biogeochemistry data is necessary to understand present and future changes in land-to-ocean fluxes. Here, we present a high-frequency, 4.5-year-long dataset from a sampling program of the Lena River's biogeochemistry, spanning April 2018 to August 2022. The dataset comprises 587 sampling events and measurements of various parameters, including water temperature, electrical conductivity, stable oxygen and hydrogen isotopes, dissolved organic carbon concentration and 14C, coloured and fluorescent dissolved organic matter, dissolved inorganic and total nutrients, and dissolved elemental and ion concentrations. Sampling consistency and continuity and data quality were ensured through simple sampling protocols, real-time communication, and collaboration with local and international partners. The data is available as a collection of datasets separated by parameter groups and periods at https://doi.org/10.1594/PANGAEA.913197 (Juhls et al., 2020b). To our knowledge, this dataset provides an unprecedented temporal resolution of an Arctic river's biogeochemistry. This makes it a unique baseline on which future environmental changes, including changes in river hydrology, at temporal scales from precipitation event to seasonal to interannual, can be detected. [ABSTRACT FROM AUTHOR]

As a response of the coastal oceans to more severe anthropogenic disturbance, increasing coastal primary production has been more frequently observed in recent years. This raises the question of howthis progressive change reshapes the long-term carbonsequestration in thecoastal oceans. With this question inmind, we investigated the sediment organic matter (OM) preserved on the shelf of the northern SouthChina Sea (NSCS) where high primary production has been observed. Across this sediment core, relatively lowtotal organic carbon content of around 0.60%was observed. Fatty acids with less carbon numbers exhibit exponential decreases downward with degradation rate constants ranging from 0.10 to 0.17 y-1, no matter they were from single sources (14:0 presumably from marine OM and ai-15:0, i-15:0, 15:0 from bacterial OM) or mixed sources (16:0). Meanwhile fatty acids with more carbon numbers, either 18:0 and 24:0 from mixed sources, or 26:0 and 28:0 presumably fromterrestrial input, were less varied inconcentrationswithdepth. Thisdemonstrates a preferential decomposition of labile fatty acids during the early diagenesis of coastal sediment organicmatter. A decrease of labile fatty acids δ13Cvalueswas observed with the decomposition, from which kinetic isotope fractionations were predicted ranging from 0.7 to 1.5‰. This provides an isotopic constraint of the mixing model to quantify labile organicmatter from terrestrial input and local phytoplankton production, from which declined contribution of local phytoplankton production to labile fatty acids was identified in more recent sediment. This finding together with the low organic carbon content and rapid removal of fatty acids in the top sediment, demonstrates the poor preservation of labile organic matter on the shelf of NSCS, implying that the increasing primary production has not enhanced the coastal carbon sequest ration yet, but rather leads tomore intensified respiration with a potential risk toincrease the CO2 outgassing fromthe coastal oceans. [ABSTRACT FROM AUTHOR]

The intrusion of relatively warm water onto the continental shelf is widely recognized as a threat to Antarctic ice shelves and glaciers grounded below sea level, as enhanced ocean heat increases their basal melt. While the circulation of warm water has been documented on the East Antarctic continental shelf, the modes of warm water transport from the deep ocean onto the shelf are still uncertain. This makes predicting the future responses of major East Antarctic marine-grounded glaciers, such as Totten and Ninnis glaciers, particularly challenging. Here, we outline the key role of submarine canyons to convey southward flowing currents that transport warm Circumpolar Deep Water toward the East Antarctic shelf break, thus facilitating warm water intrusion on the continental shelf. Sediment drifts on the eastern flank of the canyons provide evidence for sustained southward-directed flows. These morpho-sedimentary features thus highlight areas potentially prone to enhanced ocean heat transport toward the continental shelf, with repercussions for past, present, and future glacial melting and consequent sea level rise. Sediment drifts record long-lasting southward flowing currents within submarine canyons, which convey warm Circumpolar Deep Water toward the East Antarctic shelf break, thus facilitating warm water intrusion on the continental shelf. [ABSTRACT FROM AUTHOR]

The Brazilian marine biogeographical province (SW Atlantic) hosts coral and rocky reefs that cover ~27 degrees of latitude and are distributed along a relatively narrow continental shelf and four oceanic islands and archipelagos. The broad gradients in temperature, productivity and salinity shape patterns of biodiversity and lead to distinct local communities within the province. Although existing research has helped to unveil spatiotemporal patterns of marine diversity in this province, data availability and scale have limited broader inferences on the main processes shaping biodiversity. Here, we bring together 16 datasets (n = 11 for reef fish, n = 5 for benthic reef organisms) comprising 22 years of research conducted across most of the Brazilian province. These datasets are unprecedented in terms of temporal, spatial, and taxonomic coverage. For example, eight datasets (six for reef fish, two for benthos) span seven (fish monitoring in Rio Grande do Norte) to 18 years (fish monitoring in Arraial do Cabo, Rio de Janeiro) of survey data. Also, these datasets contain data collected in priority areas for conservation in the Brazilian province, such as the Abrolhos Bank and the Trindade island. The data comprise detection and fish count/benthic cover data for 24,498 sampling events deployed at 55 locations, formatted according to the Darwin Core Standard, being therefore interoperable with other existing datasets. The 11 fish datasets comprise the detection and counting of 361 fish taxa (312 identified at species level, 49 identified at genus, subfamily and family) from 178 genera, 71 families and 2 classes (Teleostei and Elasmobranchii). The five benthic datasets comprise the description of the detection and cover of 81 taxa, 82 genera, 68 families, 15 classes, and 4 kingdoms (Animalia, Bacteria, Plantae, Chromista). By making this an open-access resource, we share with the public the result of two decades of federal and state funding for scientific research on Brazilian reefs. [ABSTRACT FROM AUTHOR]

Antarctic Bottom Water has been warming in recent decades throughout most of the oceans and freshening in regions close to its Indian and Pacific sector sources. We assess warming rates on isobars in the eastern Pacific sector of the Southern Ocean using CTD data collected from shipboard surveys from the early 1990s through the late 2010s together with CTD data collected from Deep Argo floats deployed in the region in January 2023. We show cooling and freshening in the temperature‐salinity relation for water colder than ∼0.4°C. We further find a recent acceleration in the regional bottom water warming rate vertically averaged for pressures exceeding 3,700 dbar, with the 2017/18 to 2023/24 trend of 7.5 (±0.9) m°C yr−1 nearly triple the 1992/95 to 2023/24 trend of 2.8 (±0.2) m°C yr−1. The 0.2°C isotherm descent rate for these same time periods nearly quadruples from 7.8 to 28 m yr−1. Plain Language Summary: Cold winds blowing over polynyas (areas of ice‐free water) on the Antarctic continental shelf create sea ice, forming very cold and somewhat salty, hence very dense, waters. These dense shelf waters descend the continental slope to the abyss, mixing with adjacent waters to form Antarctic Bottom Water (AABW). AABW spreads northward from there, filling much of the global abyssal ocean as it mixes with warmer, lighter waters above. AABW has been warming on pressure surfaces, freshening and cooling on density surfaces, and reducing in volume (contracting). These changes are likely a result of melting Antarctic ice sheets, which freshen the shelf waters, making them less dense, hence less able to sink to the bottom. We compare profiles of ocean temperature and salinity in the eastern Pacific sector of the Southern Ocean collected in 2023 and 2024 by robotic freely drifting profilers to data collected from ships from the early 1990s to the late 2010s. We find all of the above listed changes, but also acceleration of the warming, with the rate from 2017/18 to 2023/24 being nearly triple the rate from 1992/95 to 2023/24. The contraction rate has nearly quadrupled. This acceleration has been predicted by high‐resolution climate model simulations. Key Points: Antarctic Bottom Water (AABW) changes in the east Pacific sector of the Southern Ocean are assessed using Deep Argo and ship‐based CTD profilesBottom water warming rates from 2017/18 to 2023/24 nearly triple compared to 1992/95 to 2023/24 rates, contraction rates nearly quadrupleAABW cooling and freshening on isopycnals is also observed in the region, relative to older Circumpolar Deep Water [ABSTRACT FROM AUTHOR]

Major environmental, climate and sealevel changes occurred in the Western Tethyan Realm during the late Sinemurian to early Pliensbachian time interval. Here, we examine how these changes affected the taxonomic composition of radiolarian fauna. Radiolarian assemblages were collected on Mount Rettenstein (Northern Calcareous Alps) from a siliceous limestone and marl succession, deposited in a well‐oxygenated basin a few hundred metres in depth on the continental shelf at the western edge of the Neotethys Ocean. Radiolarian research was complemented with elemental and isotope geochemistry on bulk carbonate samples. The siliceous microfaunas below and above the stage boundary consist of more than 80% sponge spicules and less than 20% radiolarians, with a strong predominance of the Order Spumellaria. The Nassellaria to Spumellaria abundance ratio ranges from 1:5 to 1:3. At the Sinemurian–Pliensbachian transition, a significant drop in diversity occurred, accompanied by a substantial change in relative abundances of radiolarian taxa. The most severely affected groups were surface‐dwelling radiolarians (Angulobrachiidae, Hagiastridae, Pantanelliidae; mostly Gorgansium, Poulpidae and Ultranaporidae), which almost or completely disappeared. In contrast, Archaeocenosphaera, Praeconocaryomma, Zhamoidellum and Lantus became abundant and were apparently the most resistant to environmental stress. The changes in radiolarian assemblages were local and probably induced by the end‐Sinemurian sealevel drop that transformed the area into a semi‐enclosed basin with restricted ocean circulation. The exchange of water masses and thus radiolarian faunas with the open sea was reduced and their productivity may have been lowered by the lower inflow of fertile waters from the ocean. [ABSTRACT FROM AUTHOR]

Growing evidence suggests that complex spatial structure occurs within the Scotian Shelf and southern Grand Banks (SSGB) Atlantic halibut stock, yet large knowledge gaps remain about diversity of migratory and spawning behaviors. Here, 71 pop-up satellite archival tags were deployed on large Atlantic halibut (FL: 87–166 cm) between 2012 and 2020. Migration tracks were successfully reconstructed for 43 fish using a hidden Markov geolocation model, and temperature and depth time series were available for an additional nine fish (total n = 52). Five migratory behavior categories were identified: shelf residency, slope residency, shelf-channel migration, shelf-slope migration, and dispersal. High-resolution data for four of 20 physically recovered tags provided evidence of putative spawning behavior in deep channels on the continental shelf and along the continental slope between January and February. Additionally, four halibut displayed previously undocumented periods of sustained, oscillatory vertical movements along the continental slope between November and February. The high migratory diversity observed in this study provides support for the existence of multiple resident and migratory contingents in the SSGB stock in the apparent absence of significant genetic structure. [ABSTRACT FROM AUTHOR]

Water exchange in the Luzon Strait (LS) is critical for layered circulation in the South China Sea (SCS); however, observational evidence of sandwich‐like water exchange is scarce. This study presents a comprehensive analysis of the meridional and zonal spatial patterns of water exchange in the upper and middle LS, along with its seasonal variations in a sigma–pi diagram using Argo profiles. As observed viewed from the perspective of SCS, inflow and outflow occur in the upper and middle layers, respectively. Upper‐layer Kuroshio intrudes into the SCS primarily in the northern and central regions of the LS, extending along the continental shelf into the inner SCS. A significant middle‐layer eastward outflow is evident at 26.7–27.56 kg/m3 (500–1,500 m) in the northern part of the strait, extending to 123°E. The Kuroshio intrusion intensifies during the winter, whereas the middle‐layer outflow is most pronounced in the autumn. Plain Language Summary: Understanding the circulation in marginal and inland seas is closely tied to comprehending the exchange of water between straits connecting neighboring oceans. The Luzon Strait, as a semi‐enclosed marginal sea, holds a pivotal role in shaping the layered circulation in the South China Sea. This study utilizes an extensive data set of Argo profiles to provide observational evidence of a layered zonal water exchange in the upper and middle Luzon Strait, offering detailed insights into the meridional and zonal patterns of water exchange and how they vary with the seasons. It reveals that inflow and outflow processes occur in the upper and middle layers observed viewed from the perspective of South China Sea, respectively. The upper‐layer intrusion of the Kuroshio is more prominent during the winter, while the middle‐layer outflow is most noticeable in the autumn. This research enhances our understanding of water exchange in the Luzon Strait and contributes to our knowledge of processes like water renewal, heat and salt budgets, and biogeochemical cycles in the South China Sea. Key Points: A novel insight into water exchange in the upper and middle Luzon Strait is provided using the sigma–pi diagramMeridional distribution of inflow (outflow) zonal water exchange in the upper (middle) Luzon Strait are describedUpper‐layer inflow was enhanced in winter, whereas middle‐layer outflow was significant during the autumn [ABSTRACT FROM AUTHOR]

The bottom boundary layer (BBL) dynamics play an important role in regulating the energy, momentum balance, and circulation in the shallow shelf areas. Unlike previous studies that disconnected BBL with background variable shelf circulation, we investigate the dynamic connection between the wind‐driven shelf circulation and BBL dynamics, and show the spatial characteristics of BBL dynamics in response to three‐dimensional (3D) heterogeneous transport over the highly variable shelf topography in the Northern South China Sea. Our process‐oriented modeling study demonstrates that the mixing dynamics and upslope buoyancy transport over varying shelf topography alter the spatial variability of BBL dynamics. Driven by southwesterly upwelling‐favorable winds, the along‐shelf current generated a frictional upslope Ekman transport. The along‐isobath pressure gradient force (PGFx∗ $PG{F}^{{x}^{\ast }}$) formed by the flow‐topography interactions over the meandering shelf induces the geostrophic cross‐isobath transport. The downwave (upwave) PGFx∗ $PG{F}^{{x}^{\ast }}$ enhances (offset) the frictional upslope transport over the east (west) of the shelf that has a concaving (uniform) bottom topography. Over the eastern shelf with concave isobaths, the intensified PGFx∗ $PG{F}^{{x}^{\ast }}$ and upslope cross‐isobath dense water transport strengthen stratification and weaken the effect of bottom stress‐induced mixing, limiting the development of the BBL. The antithesis occurs over the western shelf, where a small bottom stress controls the BBL. River discharge and the tidal current modulate the alongshore current, upslope transport, bottom stress intensity, and BBL development. We model the trajectory of seabed particles as they respond to the BBL dynamic regimes, and find that high (low) concentration, short (long) suspension time, and strong (weak) shoreward transport occurover the eastern (western) shelf, respectively. Plain Language Summary: This study investigated the dynamics impact of wind‐driven upslope transport on the bottom boundary layer (BBL). The BBL is a thin, turbulent layer of water above the seafloor that plays an important role in regulating the transport of sediment and other substances, as well as the energy and momentum balance in shallow shelf waters. We used a process‐orientated numerical model to investigate how wind‐driven currents interact with the shelf topography and what is the impact of the interaction on forming different BBL regimes in the northern South China Sea. We found that the current‐induced instability (determined by current intensity) and the upslope buoyancy transport‐induced stabilizing process (determined by current direction) jointly balance the BBL dynamics. Topographic characteristics over the southwestern and southeastern shelves off the Pearl River Estuary (PRE) regulated the intensities and directions of the bottom layer currents, controlled dynamics balance in the BBL and thus formed different BBL regimes. The BBL was further modulated by the river plume from the PRE and tidal currents over the shelf. The BBL dynamics is highly variable due to topographically regulated wind‐driven circulation and transport over the continental shelf. Key Points: The competition between flow‐induced shear mixing and upslope buoyancy transport governs the bottom boundary layer dynamics over a variable shelfThe mixing and buoyancy transport are highly regulated by variable flow‐topography interaction and modulated by plume and tidal forcingA varying bottom boundary layer shapes the characteristics of particle transport [ABSTRACT FROM AUTHOR]

A long‐standing hypothesis is that the steady along‐shelf circulation in the Northwest Atlantic (NWA) coastal ocean is driven by buoyancy input from continental freshwater runoff. However, the forcing from the freshwater runoff has not been adequately evaluated and compared with other potential driving mechanisms. This study investigates the roles of both wind stress and freshwater runoff in driving the mean along‐shelf flow in the NWA coastal ocean and examines other potential drivers using a newly developed high‐resolution regional model with realistic forcing conditions. The results reveal that wind stress has a larger impact than freshwater runoff on the overall mean circulation and along‐shelf sea‐level gradient on the NWA shelf. While the continental freshwater input consistently contributes to the equatorward along‐shelf flow and higher sea level along the coast, wind stress is more effective for the setup of the broad‐scale circulation pattern by driving the along‐shelf flow on the Labrador Shelf and opposing the flow in the Mid‐Atlantic Bight and on the Scotian Shelf. In addition to the local wind and continental runoff, the sub‐Arctic inflow from higher latitude is an essential part of the NWA shelf circulation system. This remote driver directly contributes to the along‐shelf flow and insulates the shelf flow from the Gulf Stream on the southern shelves. Plain Language Summary: This study addresses a long‐standing question of what drives the mean equatorward flow along the Northwest Atlantic continental shelf. The results show that the mean along‐shelf flow is influenced more by wind stress than local buoyancy forcing resulting from the freshwater discharges from rivers and glaciers, which has long been considered the dominant driver of the along‐shelf circulation. Remote forcing through inflow from higher latitude is also important in maintaining the broad‐scale mean along‐shelf flow and sea level. This work also provides updated views of the circulation dynamics and momentum balance of the mean along‐shelf circulation, contributing to the understanding of both the current and future states of our ocean and climate systems. Key Points: Wind forcing plays an important role in setting up the mean along‐shelf flow in the Northwest Atlantic (NWA) coastal oceanLocal buoyancy from continental runoff is not as significant as previously hypothesizedRemote subpolar inflow is an essential part of the NWA shelf circulation system [ABSTRACT FROM AUTHOR]

The Sea of Okhotsk is a marginal sea that plays a major role in the ventilation of the North Pacific, being the key location where Dense Shelf Water (DSW) forms at the surface and sinks to the intermediate layer. The Okhotsk Sea Intermediate Water (OSIW) is a key water mass because it includes large amounts of DSW, outflows to the North Pacific, and supplies the ocean with the micronutrient iron. OSIW has been warming over the past few decades, which is attributed to a decreasing trend in DSW production. The acquisition of numerous hydrographic data after 2000 in the Kuril Basin, especially dissolved oxygen from profiling floats, offers an opportunity to better quantify the water mass composition of OSIW, and the changes in OSIW properties and DSW volume. Here, we used all available hydrographic records and a mapping technique specially adapted to polar and sub‐polar regions to revisit the Sea of Okhotsk water properties and document their long‐term changes. Our analysis revealed that the volume of heavier DSW (potential density above 26.9 kg.m−3) has decreased over the past three decades by 3,600 km3, or 15% of the volume present before 1990. This decline is nearly entirely compensated for by an increase in lighter DSW. This shift toward lighter DSW is possibly a sign of the weakening of the intermediate overturning circulation starting in the Okhotsk Sea. Additionally, we found that dense Soya Current Water only accounts for about 1% of OSIW, against the 5% previously estimated. Plain Language Summary: The water of the Sea of Okhotsk is a mix of several water masses which includes the Dense Shelf Water (DSW), a water mass generated in winter via sea ice formation. When sea ice forms, the surface water salinity and density increase, and the cold DSW is generated as the surface water sinks to the bottom of the continental shelf while micronutrients, especially iron, are also incorporated. DSW mixes with other water masses and becomes the Okhotsk Sea Intermediate Water (OSIW) before being exported to the North Pacific where it plays an important role for both the climate and the biological productivity. In this study, we used all the temperature, salinity, and dissolved oxygen data acquired since 1930 to evaluate how global warming may have affected the composition of OSIW. We found that, over the past century, the amount of denser DSW has strongly decreased whereas that of lighter DSW has increased, which is consistent with the decline in sea ice production in the Sea of Okhotsk. This also suggests that the ventilation of the Sea of Okhotsk and the circulation of the intermediate layer of the North Pacific is weakening, which could indirectly affect the ocean's biological productivity. Key Points: The composition of the Okhotsk Sea Intermediate Water (OSIW) is reevaluated using an updated data set and a new mapping techniqueOSIW properties have changed in the long‐term (≥50 years) scale, with a decrease (increase) in the amount of heavy (light) Dense Shelf WaterThis suggests that the North Pacific intermediate overturning is weakening, which could affect the ocean's biological productivity [ABSTRACT FROM AUTHOR]

The hydrogen isotope ratio (δ2H) of lipid biomarkers from phytoplankton and terrestrial plants were measured in surface sediments from Chinese marginal seas (CMS), in order to evaluate processes affecting their spatial distribution, and by extension, the controls on organic carbon cycling in these dynamic marginal seas. The dinoflagellate sterol dinosterol and the microalgal sterol brassicasterol had low δ2H values (<−300%) near the mouth of the Yangtze River. Near the mouth of the Yellow River, dinosterol again had low δ2H values but brassicasterol had intermediate (−292 to −281%) δ2H values. This discrepancy in the δ2H values of two phytoplankton sterols may be explained by the timing of dinoflagellate production relative to that of brassicasterol producers (e.g., diatoms). The δ2H values of C16:0 fatty acid, synthesized by all organisms, had intermediate δ2H values (−199 to −178%) near the Yangtze River and lowest δ2H C16:0 values (−216 to −206%) occurred near the old Yellow River delta. The lowest δ2H C28:0 values (<−184%) occurred adjacent to rivers, suggesting that leaf‐wax lipids produced on the loess plateau, which are enriched in 2H, may contribute less to the nearshore environment than the offshore regions. Higher δ2H C28:0 values offshore may be explained by a larger contribution of leaf wax fatty acids from aerosols relative to river‐borne suspended particles. Lipid biomarker δ2H fingerprinting thus provides a new tool for deciphering the controls on organic carbon cycling and accumulation in the dynamic CMS. Plain Language Summary: Most carbon burial in the ocean occurs in continental shelf sediments even though they comprise a small fraction of the ocean area. Almost 10 percent of this nearshore carbon burial occurs in the Chinese marginal seas where the Yellow River and Yangtze Rivers discharge their massive sediment loads. This study applies a new tool, hydrogen isotope ratios in lipid biomarkers, to unravel the inner workings of the carbon cycle in the coastal seas of China. By focusing on the hydrogen bonded to carbon it is possible to determine things like where on land organic carbon was produced, where in the ocean marine organic carbon was produced, and the environmental conditions under which that organic material was synthesized. It was found that the dinoflagellate sterol dinosterol and the microalgal sterol brassicasterol had low δ2H values near the mouth of the Yangtze River where freshwater runoff with low δ2H values. The δ2H values of the C28:0 leaf‐wax fatty acid from terrestrial plants were higher than for the C16:0, owing to the isotopic enrichment of leaf water during evapotranspiration. The highest δ2H values for C28:0 occurred offshore, suggesting that leaf wax lipids produced on the loess plateau contribute substantially to the offshore region. Key Points: δ2H values of sedimentary sterols and fatty acids informs processes influencing OC cycling in Chinese Marginal SeasLowest δ2H values of phytoplankton sterols occur near Yangtze River deltaδ2H values of C28:0 and C16:0 fatty acids have different spatial patterns [ABSTRACT FROM AUTHOR]

Meltwater from the Greenland Ice Sheet can alter the continental shelf/slope circulation and cross-shelf freshwater fluxes and limit deep convection in adjacent basins through surface freshening. We explore the impacts on the West Greenland Current and eastern Labrador Sea with different vertical distributions of the meltwater forcing. In this study, we present the results from global coupled ocean/sea ice simulations, forced with atmospheric reanalysis, that are mesoscale eddy-active (∼2–3-km horizontal spacing) and eddy-permitting (∼6–7-km horizontal spacing) in the study region. We compare the West Greenland Current in mesoscale eddy-active and eddy-permitting without meltwater to highlight the role of small-scale features. The mesoscale eddy-active configuration is then used to assess the change in the eastern Labrador Sea when meltwater is added to the surface or vertically distributed to account for mixing within fjords. In both simulations with meltwater, the West Greenland and West Greenland Coastal Currents are faster than in the simulation with no meltwater; their mean surface speeds are the highest in the vertical distribution case. In the latter case, there is enhanced baroclinic conversion at the shelf break compared to the simulation with no meltwater. When meltwater is vertically distributed, there is an increase in baroclinic conversion at the shelf break associated with increased eddy kinetic energy. In addition, in the eastern Labrador Sea, the salinity is lower and the meltwater volume is greater when meltwater is vertically distributed. Therefore, the West Greenland Current is sensitive to how meltwater is added to the ocean with implications for the freshening of the Labrador Sea. Significance Statement: Our goal is to understand how the flux of freshwater across the West Greenland continental slope into the Labrador Sea is modified by meltwater from the Greenland Ice Sheet. We compare the simulations of the ocean that capture key dynamics along the West Greenland continental slope that have no meltwater, meltwater added to the ocean surface, and meltwater distributed vertically to represent the mixing within fjords. When meltwater is added, the currents along the continental slope are faster, with the greatest increase when meltwater is vertically distributed. In that case, there is enhanced freshening of the Labrador Sea because modified density gradients generate more eddies. Proper representation of the vertical structure of meltwater is important for projecting the impact of freshwater on the subpolar North Atlantic. [ABSTRACT FROM AUTHOR]

We revisit the nature of the ocean bottom pressure (pb) seasonal cycle by leveraging the mounting GRACE‐based pb record and its assimilation in the ocean state estimates produced by the project for Estimating the Circulation and Climate of the Ocean (ECCO). We focus on the mean seasonal cycle from both data and ECCO estimates, examining their similarities and differences and exploring the underlying causes. Despite substantial year‐to‐year variability, the 21‐year period studied (2002–2022) provides a relatively robust estimate of the mean seasonal cycle. Results indicate that the pb annual harmonic tends to dominate but the semi‐annual harmonic can also be important (e.g., subpolar North Pacific, Bellingshausen Basin). Amplitudes and short‐scale phase variability are enhanced near coasts and continental shelves, emphasizing the importance of bottom topography in shaping the seasonal cycle in pb. Comparisons of GRACE and ECCO estimates indicate good qualitative agreement, but considerable quantitative differences remain in many areas. The GRACE amplitudes tend to be higher than those of ECCO typically by 10%–50%, and by more than 50% in extensive regions, particularly around continental boundaries. Phase differences of more than 1 (0.5) months for the annual (semiannual) harmonics are also apparent. Larger differences near coastal regions can be related to enhanced GRACE data uncertainties and also to the absence of gravitational attraction and loading effects in ECCO. Improvements in both data and model‐based estimates are still needed to narrow present uncertainties in pb estimates. Plain Language Summary: We revisit the nature of the ocean bottom pressure (pb) seasonal cycle by leveraging the mounting data from space gravity missions and their use in constraining model‐based estimates produced by the project for Estimating the Circulation and Climate of the Ocean (ECCO). We focus on the mean seasonal cycle from both data and ECCO estimates, examining their similarities and differences and exploring the underlying causes. Despite substantial year‐to‐year variability, the 21‐year period studied (2002–2022) provides a relatively robust estimate of the mean seasonal cycle. The pb annual cycle tends to dominate but the semi‐annual cycle can also be important in some regions. Amplitudes are enhanced near shallow coastal regions and can also vary more strongly across the coastal zone, pointing to the importance of changes in ocean bottom topography in shaping the seasonal cycle in pb. Comparisons of data and ECCO estimates indicate good qualitative agreement, but considerable quantitative differences in the magnitude and timing of maxima remain. Largest differences, which tend to occur near coastal regions, can be related to enhanced data uncertainties and also to the absence in ECCO of effects from gravitational attraction of land ice and water storage and related deformation of the ocean bottom. Key Points: Substantial differences remain in satellite and model‐based estimates of the mean seasonal cycle in ocean bottom pressure (pb)Differences between two satellite gravimetry products suggest largest uncertainties around many continental boundariesAbsence of gravitational attraction and loading effects and intrinsic ocean variability can lead to errors in model‐based pb estimates [ABSTRACT FROM AUTHOR]

Permeable sediments, which make up almost half of the continental shelf worldwide, are potential sources of the important greenhouse gas N2O from coastal regions. Yet, the extent to which interactions between these sediments and anthropogenic pollution produce N2O is still unknown. Here we use laboratory experiments and modeling to explore the factors controlling N2O production at a eutrophic site in a temperate shallow marine embayment (Port Phillip Bay, Australia). Our results show that denitrification is the main source of N2O production within permeable sediments, but the extent to which N2O is actually released is determined by the rate of seawater exchange with the sediment bed (which governs solute residence time within the bed). In wave‐dominated coastal areas, shallower water with more intense waves (wave height > 1 m) release the most N2O, with up to 0.5% of dissolved inorganic nitrogen pumped into biologically active eutrophic sediment being released as N2O. Our results suggest rates of N2O production in coastal permeable sediments are generally low compared to other environments. Plain Language Summary: Permeable sands cover almost half of the coastal continental shelf around the world. The permeability of sand sediments, means water can flow through these sediments in complex patterns driven by waves and currents. This flow through the sediment can control nitrous oxide and methane production which are poorly understood. This is particularly important in regions impacted by nitrogen pollution where production of these greenhouse gases can be high. Here we combine experiments and modeling to explore the factors controlling N2O production at a sandy site impacted by nitrogen pollution (Port Phillip Bay, Australia). Our results show the rate of nitrous oxide release to the water column is governed by the rate of seawater exchange with the bed. Shallower water with more intense waves (wave height exceeding 1 m) releases the most N2O, with up to 0.5% of dissolved nitrogen pumped into the sediment being released as N2O. Overall, these results suggest permeable sediments have relatively low rates of nitrous oxide release most of the time. Key Points: Coastal hydrodynamics impose an important boundary condition on the production of N2O in permeable sedimentsLess than 0.5% of seawater dissolved inorganic nitrogen is converted to N2O due to forcing imposed by passing surface gravity wavesPermeable sediments are a relatively minor source of N2O emission in coastal waters of Port Phillip Bay [ABSTRACT FROM AUTHOR]

Given the rapid expansion of offshore wind development in the United States (US), the accurate mapping of benthic habitats, specifically surficial sediments, is essential for mitigating potential impacts on these valuable ecosystems. However, offshore wind development has outpaced results from environmental monitoring efforts, compelling stakeholders to rely on a limited set of public geospatial data for conducting impact assessments. The present study therefore sought to develop and evaluate a systematic workflow for generating regional-scale sediment maps using public geospatial data that may pose integration and modeling challenges. To demonstrate this approach, sediment distributions were characterized on the northeastern US continental shelf where offshore wind development has occurred since 2016. Publicly available sediment and bathymetric data in the region were processed using national classification standards and spatial tools, respectively, and integrated using a machine learning algorithm to predict sediment occurrence. Overall, this approach and the generated sediment composite effectively predicted sediment distributions in coastal areas but underperformed in offshore areas where data were either scarce or of poor quality. Despite these shortcomings, this study builds on benthic habitat mapping efforts and highlights the need for regional collaboration to standardize seafloor data collection and sharing activities for supporting offshore wind energy decisions. [ABSTRACT FROM AUTHOR]

Once fishes and rivers are intrinsically connected, historical events such as river captures and the reconfiguration of palaeodrainages affect population structure and species distribution. However, direct evidence of these events remains limited.We aimed to directly infer putative connections between adjacent river basins to understand genetic and geographical patterns in populations and species of the 'Geophagus' brasiliensis complex. For that, we analysed 174 sequences of the mitochondrial gene cytochrome c oxidase subunit I (COI) from five species along 35 sites within and near a coastal basin in northeastern Brazil. Based on haplotype network, palaeodrainage reconstruction, geological inferences of river captures and analyses of molecular variance (AMOVAs), we tested how the genetic structure could be associated with variable patterns of habitat connectivity through time.In general, high levels of genetic variation were identified, including shared haplotypes among drainages for most species. AMOVA suggested that drainage rearrangements between adjacent basins were the main drivers of genetic diversification in the 'G.' brasiliensis complex.Our study refuted dispersal routes via the continental shelf, whereas eight putative river captures suggested historical connections that enabled gene flow among drainages until recent interruption. These results provide novel insights on the role of riverscape evolution on the biogeography of neotropical ichthyofauna. [ABSTRACT FROM AUTHOR]

This study reconstructs recent changes (1880–2017) in sea-ice conditions, using biomarkers (IP 25 and phytoplankton sterols) from three sediment cores located in a transect across Belgica Trough, on the Northeast Greenland continental shelf. These results are evaluated using instrumental and historical data from the same region and time period. Over the entire study period, IP 25 concentrations are highest at the inner shelf (site 90R) and decrease towards the mid-shelf (site 109R), with lowest values found at the outer shelf (site 134R). The PIP 25 index yields the highest sea-ice cover at sites 109R and 90R and the lowest at 134R, in agreement with observational records. A decline in sea-ice concentration, identified visually and using change-point analysis, occurs from 1971 in the observational sea-ice data at sites 90R and 109R. A change in sea-ice concentration occurs in 1984 at site 134R. Sea-ice conditions in these years aligns with an increase in sterol biomarkers and IP 25 at all three sites and a decline in the PIP 25 index at sites 90R and 134R. The outcomes of this study support the reliability of biomarkers for sea-ice reconstructions in this region. [ABSTRACT FROM AUTHOR]

Large and diverse Eocene otolith assemblages have been described from the US Gulf and Atlantic coastal plains, various basins in Europe, and New Zealand. Here we described a highly diverse otolith association from the middle Eocene (Lutetian and Bartonian) strata of southern California, San Diego County, which was retrieved from the heritage of John E. Fitch (1918-1982) in the archives of the Ichthyology Department of the Natural History Museum of Los Angeles County, Los Angeles, Califronia. The collection represents the first Eocene otolith assemblage described from the Northeastern Pacific and stems from two localities: the Ardath Shale at Black’s Beach in the Torrey Pines Park just south of Black’s Canyon Road and north of the Salk Fault on the Pacific shore face, and the MissionValley Formation from the west-facing graded hill just east of the Miramar Water Treatment Plant near the southern shore of Miramar Reservoir. The Ardath Shale was deposited on the deep shelf and continental slope while the Mission Valley Formation represent an inland, nearshore environment during times of the maximum transgression. A total of more than15,000 otoliths were found representing 96 species of which 53 are described as new and 12 remain in open nomenclature. The fauna of the Ardath Shale is distinctly richer containing 88 species while the one from the Miramar Reservoir site yielded 38 species. The low diversity at the Miramar Reservoir site is thought to be related to the shallow-water environment in which it was deposited whereas the high diversity at Black’s Beach reflects a mixture of shelf and bathyal fishes. In addition, 24 new otolith-based genera are established, four of which are in the category “incertae sedis”. Furthermore, five new species are described from a comparative otolith collection from the US Gulf Coast Eocene and one new species from a comparative collection from the Lutetian of Balegem in Belgium. The Eocene otolith-based fish fauna from California is assessed for its paleoecological, paleobiogeographic and evolutionary significance. Particular emphasis is directed towards the elucidation of the evolution of the early Ophidiiformes, which during the early Paleogene were predominantly adapted to warm, clastic shallow-water environments and there were competing in abundance and diversity with other percomorphs (e.g., perciforms s.l.). A warm Eocene paleobioprovince is proposed for the Californian fish fauna which is not related to today’s endemic Northwest Pacific fish fauna along the regime of the cold-water California Current. [ABSTRACT FROM AUTHOR]

The bluntnose sixgill shark (Hexanchus griseus) is a wide‐ranged deep‐water shark species found off continental and insular shelves. Despite its global distribution, little is known about the reproductive ecology of the species, particularly with regard to the location and timing of important phenological events such as mating and pupping. In this study, we report the landing of a neonate H. griseus individual from an artisanal fishing camp in Baja California Sur, Mexico. This represents only the ninth confirmed record of the species from the Mexican Pacific and the first to report a neonate specimen in Mexican waters. We discuss this specimen in the context of the environmental conditions in which it was found, ultimately suggesting that these shallow coastal waters may be an important pupping ground for H. griseus in the region. Furthermore, the specimen was found during the winter months (whereas all previous reports have suggested H. griseus pups during the summer), implying regional variation in reproductive periodicity, or the presence of multiple reproductive events per year. This study provides novel insight into the reproductive biology of H. griseus and the ecological characteristics of the species in the Northern Mexican Pacific. [ABSTRACT FROM AUTHOR]

Myctophids are central in ocean food webs, yet knowledge of the ecology of larval stages is sparse. We investigated if larval feeding ecology is different in continental shelf break waters compared to waters off oceanic islands in the western Tropical Atlantic. The larvae were collected through diurnal and nocturnal oblique hauls using a Bongo net and stomach contents were analyzed. The larvae ranged between 2.27 and 16.5 mm in standard length. Diet composition was different in the slope and islands (Permutational Multivariate Analysis of Variance (PERMANOVA), P  < 0.001). Diatoms (mainly Thalassiosira spp. and fragments of diatoms) were numerically important in the diet at the slope site (69% of relative importance). Copepods were the most relevant prey (71% of relative importance) near the islands. Copepods were the biomass-dominant dietary item at both areas, alongside ostracods near the islands. Smaller prey items were more important for smaller larvae, particularly those measuring up to 4 mm. Larger prey became relatively more important as the larvae grew to at least 8 mm. Larvae fed mostly during the daytime regardless of their size class. [ABSTRACT FROM AUTHOR]

The North Sea region boasted one of the world's most important fisheries for many centuries. Climate directly and indirectly influences the development and survival of many important pelagic fish in the North Sea ecosystem. One indirect influence is the food availability in the form of phyto- and zooplankton abundance, which is strongly controlled by environmental factors. One of these environmental factors is local sea surface temperatures. A negative correlation between zooplankton abundance and sea surface temperature is well established for the epeiric sea on the European continental shelf. Continuous temporal observations of North Sea zooplankton production only exist since 1958. Therefore we developed a Historical Plankton Index (HPI) from 800 CE onwards to extend our record of temperature-driven zooplankton abundance in the North Sea over a multi-centennial time scale. For this we used the North Atlantic temperature reconstructions and associations between zooplankton abundance and contemporary sea surface temperatures established applying a General Additive Modelling (GAM) approach. We then examined the association between the HPI and historical landings from the Dutch commercial herring fishery in the 17th century to test the utility of our HPI. We examine the potential influence of food availability (in terms of zooplankton abundance) on the fishery, the evolution of which is often only considered in terms of human influences such as conflict, fishing gear and demand for fish as a commodity. We find that under certain conditions the HPI can explain 20% of the variability in Dutch herring landings. This highlights the importance of developing long-term and large-scale indices of natural marine ecosystem dynamics to understand the historical fortunes of the commercial fishing industry. The results are directly relevant to the United Nations' sustainable development goal 14 – life below water. [ABSTRACT FROM AUTHOR]

Finding prehistoric sites, on the sea floor off the United States, has proven to be a difficult task. Over four decades of innovative attempts have produced few discoveries. This discussion outlines the difficulties in finding submerged prehistory on the sea floor, examines current methodology(ies), and presents a new methodology that demonstrates promise based on research conducted over the past decade. The purpose of this discussion is to outline the problems facing archaeologists searching the sea floor for archaeological sites. It is less of a critique of past efforts and methodologies used in those attempts. Without those efforts, a reason for developing a different methodological approach would be unnecessary. Any "one size fits all" methodology is limiting, and the scant number of marine archaeological sites located off the shores of the United States can attest to the need for practitioners to continue refining their methods. This is especially the case on the continental shelf of the eastern United States, where sediment cover is often meters, or several meters, thick. This opportunistic methodology developed on the continental shelf of the Georgia Bight, western Atlantic Ocean, has located intact paleo-landforms with in situ, palaeoecological remains thereby offering promise for future archaeological discoveries. [ABSTRACT FROM AUTHOR]

The present study aims to detect early changes in the community structures of macrozoobenthos and indications of their recovery following sand excavation activities in the soft bottom of the southern continental shelf area, Korea strait, from August 2002 to October 2005. About 10 million m3 of relict sandy sediments were excavated from a 9 km2 area over 18 months, from June 2002 to April 2004. The sand excavation and collection activities in the study area increased the sand amount in the residual sediments due to the complete loss of fine surface sediments. However, the fine particles in the turbidity flumes produced by sand hopper vessels were deposited in neighboring zones. The overall ecological impacts of the sand excavation activity are the rapid loss of macrobenthic animals in the central region of the excavation area and the decrease in densities of some disturbance-sensitive macrobenthos, such as Ampelisca spp. and Photis longicaudata that are dominant in the marginal parts of the excavation area. The burrowing polychaete Ophelina acuminata and the opportunistic tube-building polychaete Paraprionospio coora were the most predominant species in the central region of the study area following 12 months. The affected regions showed decreases in the abundance and recovery of the macrozoobenthic fauna species depending on the changes in sediment properties induced by the sand excavation activities, such as sediment loss and material deposition materials. One and a half years after the cessation of the sand excavation activities, the density of the most abundant species was increased and comparable to those in the reference area. In addition, the biological characteristics of the macrobenthic community showed indications of recovery to their previous status, with different faunal compositions and densities. Further long-term ecological monitoring of the macrobenthic communities is necessary to comprehensively assess their recovery processes following sand excavation in the study area. [ABSTRACT FROM AUTHOR]

This paper provides first information about possible occurrence of the myxosporean genus Kudoa in fish of the World Ocean and, in some cases, in associated freshwater bodies at different depths. An analysis of the theoretically assumed site preference by Kudoa of different habitat depths of their fish hosts in the World Fauna is made for the first time. It is revealed that all species of the myxosporean genus Kudoa can be found in coastal shelf zones, of which 90 species (70.8% of the total) occur exclusively in the shelf zone, and the hosts of 50 Kudoa species (39.4%) live in its shallowest part (down to 50 m). 16 species (12.6%) and 14 species (11%) of this genus can be found at depths from the shelf to 500 meters and 1000 meters, respectively. From 1 to 3 species of Kudoa can be encountered theoretically at 1500 m to 3000 m, which is from 0.8 to 2.4% of all known representatives of these parasites. [ABSTRACT FROM AUTHOR]

An offshore installation is exposed to ship collision risk from in-field and passing vessels. Both categories of collision have occurred on the United Kingdom Continental Shelf (UKCS), and both have the potential to result in catastrophic damage to the installation, although to date only significant consequences have been observed in UK waters. World-wide, catastrophic collisions with installations have occurred resulting in severe damage to vessels and installations, leading to loss of life and environmental damage. This led to the authors investigate the occurrence and reporting of ship to platform collisions on the UKCS 1971–2017. It was found that there were periodic fluctuations in the occurrence of collision accidents. This research analyses the accident trends in order to determine the whether the fluctuations were a regular occurrence and, if so, what was the cause. 511 ship to platform collision incidents between 1971 and 2017 were subject to analysis, in terms of damage classification, the vessel type, month of occurrence and a comparison of the release of regulations with the fluctuation of incidents. Subsequently, this analysis has identified a key trend between the reporting of offshore collision incidents and the release and enforcement of offshore Safety Case regulations. [ABSTRACT FROM AUTHOR]

This paper recommends end to end quality assurance methods and quality control tests for High Frequency Radar Networks. We focus on the network that is operated by the Mid Atlantic Regional Association Coastal Ocean Observing System (MARACOOS). The network currently consists of 38 radars making real-time measurements of the surface currents over the continental shelf for a variety of applications including search and rescue planning, oil spill trajectory modelling and providing a transport context for marine biodiversity observing networks. MARACOOS has been delivering surface current measurements to the United States Coast Guard (USCG) since May 2009. Data quality is important for all applications; however, since the USCG uses this surface current information to plan life-saving missions, delivery of the best quality data is crucial. We have mapped the components of the HF radar data processing chain onto the data levels presented in the NASA Earth Science Reference Handbook and have applied quality assurance and quality control techniques at each data level to achieve the highest quality data. There are approximately 400 High Frequency radars (HFRs) deployed globally and the presented techniques can provide a foundation for data quality checks and standardization of the data collected by the large number of systems operating today. [ABSTRACT FROM AUTHOR]

Nearshore waters are utilized by elasmobranchs in various ways, including foraging, reproduction, and migration. Multiple elasmobranch species have been previously documented in the nearshore waters of North Carolina, USA, which has a biogeographic break at Cape Hatteras on the Atlantic coast. However, comprehensive understanding of the elasmobranch community in this region is still lacking. Monthly year-round trawling conducted along two ocean transects (near Cape Lookout and Masonboro Inlet in 5 to 18 m depth) in Onslow Bay, North Carolina provided the opportunity to examine the dynamics and seasonal patterns of this community using a multivariate approach, including permutational multivariate analysis of variance and nonparametric BIO-ENV analysis. From November 2004 to April 2008, 21,149 elasmobranchs comprised of 20 species were caught, dominated by spiny dogfish (Squalus acanthias) and clearnose skate (Rostroraja eglanteria). All species exhibited seasonal variation in abundance, but several key species contributed the most to seasonal differences in species composition within each transect. Spiny dogfish was most abundant in the winter at both locations, comprised mainly of mature females. Although clearnose skate was caught in all seasons, the species was most abundant during the spring and fall. Atlantic sharpnose (Rhizoprionodon terraenovae) was one of the most abundant species in the summer, and two distinct size cohorts were documented. Temperature appeared to be the main abiotic factor driving the community assemblage. The extensive year-round sampling provided the ability to better understand the dramatic seasonal variation in species composition and provides new information on the relative abundance of several understudied elasmobranch species that may be of significant ecological importance. Our results underscore the importance of inner continental shelf waters as important elasmobranch habitat and provide baseline data to examine for future shifts in timing and community structure at the northern portion of the biogeographic break at Cape Hatteras. [ABSTRACT FROM AUTHOR]

The east coast of India is highly prone to devastating winds, torrential rainfall, and storm surges caused by tropical cyclones. The storm surge is affected by ocean basin characteristics involving the width and slope of the continental shelf. The bed roughness plays a major role in surge formation. The east coast of India is characterized by a broader shelf in the north and a narrow shelf in the south. This paper uses a hybrid Finite Volume Method–Finite Element Method based Shallow water equation (SWE) solver to predict the storm surges during different cyclone events, and the roughness parameter Manning's n is used in bed friction calculations. The bottom friction coefficient parameterization involving bed roughness is used to calibrate the resistance to flow in the numerical model. The calibration exercises are carried out with different values of n for each surge simulations for different cyclones to predict the surface elevation. Different statistical parameters against the measured values are used to analyze the impact of varying n values on predicted surge levels, and the most suitable n value is carefully chosen. The relationship between n and the bed slope is established as an expression, to replace the formulations involving Manning's n, thereby minimizing the usual computational efforts. The performance of the novel bed friction formulation involving the physical parameter in bed slope is demonstrated through statistical evaluations. [ABSTRACT FROM AUTHOR]

[Objective] The Carboniferous system of the Ounan Depression in the eastern Qaidam Basin is a key area for oil and gas exploration in new regions and strata. Drilling and outcrops reveal significant differences in the sedimentary characteristics of the Upper Carboniferous strata across the plane. Previous research, mainly based on outcrop and drilling data, has focused on longitudinal sedimentary evolution and the overall sedimentary background, leaving the distribution characteristics of sedimentary facies unclear. This uncertainty affects the deployment of oil and gas exploration in the Upper Carboniferous of the eastern Qaidam Basin. [Methods] The article focuses on the Upper Carboniferous strata of the Ounan Depression. It predicts the distribution characteristics of sedimentary facies under the guidance of sedimentary model theory using a limited amount of drilling data and 2D seismic data. Utilizing 2D seismic data from the Ounan Depression, it also conducts a detailed study of the internal structure and external geometric features of seismic reflections using seismic facies identification technology. [Results] The comprehensive study identifies six types of seismic facies within the Upper Carboniferous of the Ounan Depression: parallel sheet, sub-parallel sheet, mounded, wedge-shaped, oblique foreset, and chaotic. A planar assemblage map of the seismic facies was developed. By integrating regional geological data, outcrops, well logs, and seismic data, and under the guidance of seismic sedimentology and continental shelf sedimentation theory, the relationship between seismic facies and sedimentary facies in the Upper Carboniferous of the Ounan Depression was established, and the distribution characteristics of sedimentary facies in the study area were predicted. [Conclusion] The results indicate significant differences between the seismic facies in the western and eastern regions of the Ounan Depression. Overall, the western part exhibits lower frequency and more continuous phases compared to the eastern region; the western region also has greater monolayer thickness and a more stable sedimentary environment. From east to west, the Ounan Depression develops a sequential fluvial-delta plain sedimentary system, delta front sedimentary system, and prodelta-deep water shelf sedimentary system. [Significance] The research findings provide a scientific basis for predicting favorable reservoir distribution areas and deploying exploration targets for Carboniferous oil and gas exploration in the eastern region of the Qaidam Basin. [ABSTRACT FROM AUTHOR]