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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]

This study aimed to understand the reproductive biology and migrative behavior of the largehead hairtail Trichiurus lepturus in a tropical area, specifically off Pernambuco coast, northeastern Brazil. Commercial catches from fish corrals provided samples for analysis, including measurements, weight recording, and examination of gonads to determine its maturation stage. Reproductive analyses were performed, such as sex ratio, gonado‐somatic index, and sizes at first maturity. There was a slightly higher proportion of females among the 141 largehead hairtail specimens analysed. No significant differences were observed in length distributions between males and females. However, during the winter, significant differences were observed in length distributions for grouped sexes. The species exhibited a seasonal migratory pattern, with a higher presence on the continental shelf during the winter. The study identified strategic allocation of energy in feeding activities and temporal spacing of reproductive cycles, as indicated by the sex ratio and abundance of individuals during different seasons. Fish corrals probably do not harm largehead hairtail population off the southwestern Atlantic tropical coast, with minimal capture of individuals below the size of first maturity. The insights of the study into reproductive and migration patterns contribute to future assessments and management strategies for this species and corral fisheries. [ABSTRACT FROM AUTHOR]

Red snapper fishing (Lutjanus purpureus) is an important fishing activity for the Brazilian economy due to its export. The scarcity of up-to-date information on this system's ecology, economy, and social characteristics contributes to inefficient management. We analyze whether the commercial snapper fishery on the Amazon continental shelf is socioecologically sustainable. For this, an assessment tool was used that can be applied to fishing systems with little data, the Fisheries Performance Indicators (FPI). The results showed that the critical points of this activity are mainly related to the Ecological indicator (2.3) and the Economic indicator (2.8). The best indicator was the Community (3.8). The problems that put at risk the permanence of the activity and its maintenance are: (i) fishing for juveniles; (ii) illegal vessels; (iii) lack of collaboration of the fishing sector with science, and (iv) unreliability of data supplied. All the points mentioned make the snapper fishery on the north coast of Brazil socio-ecologically unsustainable in the long term. [ABSTRACT FROM AUTHOR]

The increase in population and rapid economic development activities increase vulnerability along the coastal areas. Coastal zones are among the planet's most dynamic regions and are susceptible to natural and anthropogenic hazards. To comprehend how risks and hazards are distributed spatially along the coast, coastal vulnerability assessment is crucial. This study aims at identifying the vulnerable zones along the coast of Kerala, India. For this, the coastal vulnerability index (CVI) is calculated by considering the physical, geological, and socio-economic parameters. The physical-geological parameters considered are nearshore bed slope, shoreline change rate, coastal elevation, tidal range, and continental shelf width. The socio-economic parameters include population density, road network, and land use/land cover. Analytical hierarchy process (AHP) is used for obtaining weights for physical-geological and socio-economic parameters. Coastal vulnerability results show that 82.40 km of the coastal stretch has a very high CVI value along the coast of Kerala, accounting for 13.87% of the total coastline. The most vulnerable stretches are along the coast of Kozhikode, Malappuram, Thrissur, Ernakulam, Alappuzha, and Trivandrum districts while Kasargod and Kannur districts have no coastal stretches with very high CVI. High population density, low nearshore bed slope, low coastal elevation, high erosion rates, built-up areas, and roads near to the coastline are some of the factors contributing to very high CVI in coastal districts of Kerala. [ABSTRACT FROM AUTHOR]

Sandy shorelines occupy ca. 80% of the coast of Mozambique, South Africa and Namibia. A geomorphological classification of sandy shorelines in the subcontinent identifies twelve major categories in four sub-regional coastal systems. The behaviour of each of the major shoreline types under rising sea level is outlined based on geological principles together with observations of former shorelines preserved onshore and on the continental shelf. Human adaptation strategies regarding shoreline change involve a binary choice (hold the shoreline in place or permit it to fluctuate) and these exert an equally important control on sandy shoreline response in the medium term as does sea-level rise itself. It is anticipated that densely urbanised sandy shorelines will be stabilised by coastal defences involving both capital works and ongoing maintenance that will be accompanied by deterioration and ultimate loss/replacement of the natural ecosystem. In contrast, currently undeveloped, natural shorelines will be permitted to adjust and will, as a consequence, survive and continue to deliver ecosystem services. The major challenge for climate-change adaptation lies in those lightly urbanised coastal areas where relatively small numbers of property owners may be, or perceive themselves to be, at risk of economic loss from shoreline change. In such cases the choice is between preserving those property interests (through sea defences) and preserving the sandy shoreline and its human and ecosystem services (via retreat). [ABSTRACT FROM AUTHOR]

The most extensive coverage of surficial sediment samples collected to date on Egypt's Nile Delta coast and shelf is needed to better define sediment dispersal patterns across this setting's rapidly eroding margin. Changes in time are now induced by River Nile sediment cutoff by dams, sea level rise, marked shelf subsidence, and regional climate changes, which have altered the amounts and components of sediments; these require replacement, along with the implementation of more effective coastal protection measures. Multiple computer-generated offshore maps depict the distributions and proportions of sand, silt, and mud; the mean grain size and standard deviation (sorting); heavy mineral concentrations; and carbonate content. Heavy mineral lobes at the coast and offshore identify former Nile branch sites. Channel lobes extending seaward resulted from their progradational phase and from the delta's altered sedimentation from the early to late Holocene. The progressive deposition and erosion of these fossil fluvial lobes, and of two active Nile channels, selectively removed their quartz and less dense minerals, thus concentrating heavy minerals on the coast and inner shelf. The prolonged dispersal of original sediment effluence from relict and recent Nile tributaries induced variable depositional patterns on the present shelf. These coastal depocenters, along with extensive sand, silt, and mud from shelf sediments, were reworked further seaward and dispersed by bottom currents, thus masking most previous onshore-to-offshore transport patterns. The major surficial features document long-term responses to the diverse dispersal that influenced the shoreline to the outer shelf deposits from the Pleistocene to the present. [ABSTRACT FROM AUTHOR]

Abstract—Sedimentation transport of 137Cs can lead to the significant accumulation of this radionuclide at depths that could not be reached through the vertical water exchange alone; therefore, a comparative assessment of its contents for different types of suspended matter (SM) and regions of the Black Sea is of particular interest. For this purpose, we have collected samples of SM and seawater at deep-water and coastal stations for the subsequent determination of the 137Cs activity in the surface water layer. To calculate the fraction of lithogenic matter, the potassium content in the SM was additionally determined. The range of 137Cs content on SM at different stations differed by more than an order of magnitude: from 7 to 111 Bq/kg for specific activity, and from 0.03 to 0.69% for its content on SM, in % of the total content in the surface water layer. Stations located farther away from the coast were characterized by the lowest percentage of 137Cs in SM, while its content at the coastal stations was more variable. The comparison of the lithogenic and biogenic contribution to SM and data on 137Cs for different stations suggests that the content of this radionuclide on SM is primarily determined by the dynamic variations of the lithogenic matter. Based on the 137Cs migration on SM, the Black Sea is divided into at least two types of regions. One regions are water areas far removed from sources of lithogenic matter where SM is formed mainly due to the hydrobiont activity. The 137Cs content in SM due to the predominance of biogenic matter and an insignificant concentration of lithogenic matter in this case accounts for hundredths of a percent of its total content in the surface water layer. Other regions are coastal and shelf water basins, which, on the one hand, are subjected to the significant coastal and river lithogenic runoff, and on the other, they are characterized by the elevated trophicity and biological productivity. In these water areas, 137Cs content on SM owing to the variability of biotic and abiotic factors is more variable and can fluctuate from values typical for the open sea to an order of magnitude higher. [ABSTRACT FROM AUTHOR]

Seismic lines and sediment cores collected along the shelf between Albenga and Loano (Liguria, NW Italy) allowed an unprecedented reconstruction of the characters and distribution of late Quaternary transgressive littoral deposits. Multiple seismic lines datasets and stratigraphic logs were managed within a single, GIS-based software. This approach allowed the merging, analysis, and interpretation of multimethodological datasets, greatly increasing the understanding of the study area. On seismic reflection lines, the identification of high-amplitude acoustic facies (i.e. coarse-grained deposits), coupled with the analyses of the identified paleo-morphologies, allowed the mapping of (at least) five paleo shorelines along the continental shelf at 30–40 40–60, 60–80, 80–90 and 90–100 m below sea level. Their retrogradiational geometry and terraced distribution likely indicate episodic, stepwise retreats of Late Quaternary coastal system (last 18–11 Ky), compatible with phases of fast sea level rise interspersed by long periods of sea level stillstand. [ABSTRACT FROM AUTHOR]

Heletz–Ashdod oil field is the first oil deposit to have been discovered in the Eastern Mediterranean. This deposit has been exploited until the present despite its small reserves. However, this area's tectonic–geodynamic and structural features must be studied more. Based on the integrated regional geological–geophysical analysis, it was proposed that the Heletz terrane, which includes this deposit, is the nodal structure of the Eastern Mediterranean. This terrane is a composite part of the earlier identified Mesozoic terrane belt (MTB). The Heletz terrane's essential tectonic peculiarity is the MTB's impact, rotating counterclockwise. Analysis of local geophysical data in this area (gravity, magnetic, and seismic) and regional thermal data examination testifies to the complex mosaic composition of the Heletz structure. It is proved that the crystal basement below the Heletz terrane is characterized by specific properties that do not coincide with the adjacent areas. Finally, a series of structural–paleogeographic and thickness formation maps of the Heletz–Ashdod oil field has been compiled. This investigation shed light on this area's perspectives and searched other hydrocarbon deposits in the easternmost Mediterranean coastal and shelf zones. [ABSTRACT FROM AUTHOR]

The Peninsular Malaysia Geodetic Vertical Datum 2000 (PMGVD2000) inherited several deficiencies due to offsets between local datums used, levelling error propagations, land subsidence, sea level rise, and sea level slopes along the southern half of the Malacca Strait on the west coast and the South China Sea in the east coast of the Peninsular relative to the Port Klang (PTK) datum point. To cater for a more reliable elevation-based assessment of both sea level rise and coastal flooding exposure, a new epoch-based height reference system PMGVD2022 has been developed. We have undertaken the processing of more than 30 years of sea level data from twelve tide gauge (TG) stations along the Peninsular Malaysia coast for the determination of the relative mean sea level (RMSL) at epoch 2022.0 with their respective trends and incorporates the quantification of the local vertical land motion (VLM) impact. PMGVD2022 is based on a new gravimetric geoid (PMGeoid2022) fitted to the RMSL at PTK. The orthometric height is realised through the GNSS levelling concept H = hGNSS–Nfit_PTK–NRMDT, where NRMDT is a constant offset due to the relative mean dynamic ocean topography (RMDT) between the fitted geoid at PTK and the local MSL datums along the Peninsular Malaysia coast. PMGVD2022 will become a single height reference system with absolute accuracies of better than ±3 cm and ±10 cm across most of the land/coastal area and the continental shelf of Peninsular Malaysia, respectively. [ABSTRACT FROM AUTHOR]

Here we present an optically stimulated luminescence (OSL) age estimate of 64 ± 5 ka for an offshore aeolianite and draw regional correlations (within 45 km) between the Pleistocene geological sequence offshore of the Durban Bluff, and contemporary palaeoenvironmental records from Sibudu on the South African sub-tropical east coast. Considering this age estimate within the context of high-resolution hydroacoustic data and, in particular, sub-bottom profiles, we tentatively suggest phases of dune building during marine isotope stage (MIS) 4 along the east coast of South Africa. The age and depositional characteristics of the composite Bluff-Blood Reef aeolianites suggest that dune-building events were linked to sea-level stillstands during both highstands (with deposits now preserved above water from MIS 7 and 5e) and lowstands (preserved below water, specifically, MIS 4). Aeolianite remnants of late MIS 4 age show that the wind regime during this mild glacial was dominated by winds typical of modern-day temperate latitudes; prevailing directions preserved in foresets pointing towards northerlies and southeasterlies. This is in contrast to the present-day prevailing northeasterlies and southwesterlies in the study area. We investigate the role of a narrow shelf in the characteristics of the sedimentary depositional system of the Durban Bluff and the role of southeasterlies during MIS 4 in delivering sediment to the contemporary coast. We demonstrate the value in correlating offshore and onshore Quaternary sequences, and the role that submerged deposits can play in unravelling nuances of glacial conditions on ice-free continental shelves. Broadly, the correlations that we draw between the shelf aeolianites and the archaeological record of Sibudu, supports evidence of climatic and environmental variability during MIS 4 in this area. [ABSTRACT FROM AUTHOR]

This paper presents the impact of near-bed turbulence due to only waves on a sediment bed to analyze the bedform evolutions and formation of ripples over a sloping bed of fine sediments in a laboratory flume. Measurements were made on the development of bedforms and the specific properties related to ripple formations. The geometric characteristics of ripples were recorded at multiple locations along the sloping bed in equilibrium condition. The results offered a significant understanding of the correlation between wave characteristics on a sloping bed and the shape of ripple marks. Grain size distribution analysis along the sloping bed revealed significant changes in the fine, non-cohesive sediment bed. It is interesting to note that the unimodal grain-size distribution was transformed to bimodal due to progressive surface waves. Moreover, strong spatial dependency was observed between the characteristics of waves and the arrangement of ripple forms. The parameters of ripples formed due to surface waves agree well with the predicted formulas. Results of near-bed turbulence due to surface waves are also reported. Furthermore, the study provides an understanding of the intricate relationships between waves, bed morphology, and changes in ripple marks. This knowledge can be applied to improve engineering practices in coastal regions. • Flume experiments on a sloping fine sand bed under waves of different frequencies. • Investigates complex interactions between waves and ripple formation in coastal shelf. • Impact of wave frequencies correlated with spatial variation of ripple morphology. • Modifications of near-bed turbulence on sloping bed, analogous to coastal shelf zone. • Insights the evolution of bed forms, grain sorting and ripple formation. [ABSTRACT FROM AUTHOR]

Four new species of buccinoid gastropods from the continental shelf and slope are described. Neptunea flatteryensis Clark, n. sp. and Latisipho ritteri Clark, n. sp. from depths of 134-165 m off the Cape Flattery area of Washington State, Buccinum cascadiense Clark, n. sp. found at bathyal depths of 788-1203 m, off of the coasts of Washington and Oregon, and Golikovia fitchi Clark, n. sp. found at bathyal depths of 722-1240 m off of California. [ABSTRACT FROM AUTHOR]

Production of octopus fisheries is highly variable typically due to their sensitivity to environmental conditions. Using data from four scientific research cruises conducted in 2016 and 2017, we studied the influence of the environment on the relative abundance and distribution of two co‐occurring octopus species, Octopus americanus (merobenthic) and O. maya (holobenthic), at the eastern part of the continental shelf of the Campeche Bank, a tropical upwelling area. By means of fitting hierarchical Bayesian spatio‐temporal models, we found that the relative abundance of both species decreased with depth and when salinity and temperature were higher. The residual spatial distribution showed that variability in space for both species differed between seasons. In summer, when upwelling conditions dominate, O. americanus was abundant at the eastern part of the continental shelf, while O. maya dominated in the north‐east and the coastal zone of Yucatan. In winter, when mixing conditions characterize the water column, O. americanus was abundant in coastal waters of Quintana Roo towards the north‐west, whereas O. maya occurred mostly to the north‐east. Additionally, the body weight of O. americanus decreased with depth, rocky bottoms and winter, while O. maya was smaller in shallower waters, sandy bottoms and summer. Overall, both species showed greater affinity for less saline and cooler waters, indicative of upwelling conditions. The spatial distribution differed between species and between sizes. We suggest that the ontogenetic differences would be associated with their distinct dispersal capacity during their early stages that would be under the influence of the Loop Current. [ABSTRACT FROM AUTHOR]

Insight on wave regimes along the world's coastlines is important for virtually all coastal and nearshore marine activities, installations, planning and protection. Waves are pervasive and the dominant source of energy driving extreme sea levels, the transport of pollutants and sediments, erosion, and a major contributor to risks of flooding. We quantify the global spatio-temporal wave conditions along the world's coasts and evaluate the needs for coastal Earth Observation strategies, with the aim, notably, that the derived scales of change can contribute to optimisation of these strategies. A global dominant timescale of 30 days is found in coastal wave variability that is, on average, spatially correlated just over the synoptic 5 degrees' regional scale (≈ 550 km at the equator). This regional-scale dimension suggests that the timing and design of traditional field surveys and observations relevant to a vast array of coastal activities, and which may be expensive in terms of human resources, may be complemented by information gained from satellite Earth Observation that throws light on spatio-temporal scales of wave-energy change along the world's coastlines. [ABSTRACT FROM AUTHOR]

Length‐weight relationships (LWRs) were estimated for four fish species (Catathyridium garmani, Pseudauchenipterus affinis, Cathorops arenatus, and Anchoviella brevirostris) captured at six sites on the Espírito Santo and Bahia continental shelf, Brazil. Fishes were sampled monthly for 13 consecutive months using a small‐meshed bottom trawl (measured 10.25 m in ground rope and 8.37 m in head rope, with 13‐ and 5‐mm 156 stretched mesh openings in the body and in the cod‐end). Measurements were taken for total length (TL − 0.1 cm precision) and total weight (TW − 0.01 g precision). All estimated LWRs were significant (p <.05). New maximum total lengths (TL) were recorded for three species. [ABSTRACT FROM AUTHOR]

This paper evaluates the contribution of waves to the total predicted storm surges in a Hurricane Irma hindcast, using ADCIRC+SWAN and ADCIRC models. The contribution of waves is quantified by subtracting the water levels hindcasted by ADCIRC from those hindcasted by ADCIRC+SWAN, using OWI meteorological forcing in both models. Databases of water level time series, wave characteristic time series, and high-water marks are used to validate the model performance. Based on the application of our methodology to the coastline around Florida, a peninsula with unique geomorphic characteristics, we find that wave runup has the largest contribution to the total water levels on the south and northeast coasts. Waves increase the surge on the south and northeast coasts, due to large fetch and wave runups. On the west coast, the wave effect is not significant, due to limited fetch. However, significant wave heights become greater as the waves propagate into the deep inner gulf. The continental shelf on Florida's west coast plays a critical role in decreasing the significant wave height and sheltering the coastal areas from large wave effects. Both models underpredict the high-water marks, but ADCIRC+SWAN reduces the underprediction and improves the parity with the observed data, although the scatter is slightly higher than that of ADCIRC. [ABSTRACT FROM AUTHOR]

The largest continental shelf Oxygen Minimum Zone (OMZ) in the world is formed along the Indian western shelf in the eastern Arabian Sea during the Southwest Monsoon [(SWM); June–September], which is a natural pollution event associated with the coastal upwelling. This study examines the composition, abundance, and distribution of copepods during the Northeast Monsoon [(NEM); November to February] and SWM in 50 m depth zones along the Indian western shelf in the eastern Arabian Sea. The NEM was characterised by warm, stratified, and low-salinity waters in the southeast Arabian Sea and cold, high-salinity, and well-mixed waters in the northeastern Arabian Sea. During the SWM, cold and Dissolved Oxygen (DO) deficient waters (<22 μM/0.5 ml L−1), which are the signs of coastal upwelling, were evident all along the study zone, but with more intensity off Kochi, Mangalore, and Goa in the south than off Mumbai and Okha in the north. The zooplankton total biomass and abundance showed seasonality with a general decrease during the SWM (av. 3.68 ± 1.29 ml m−3 and av. 5711 ± 3096 Ind. m−3, respectively) compared to the NEM (av. 7.37 ± 2.17 ml m−3 and av. 14,473 ± 4966 Ind. m−3, respectively). At the same time, the abundance of Polychaeta and Siphonophora showed an increase during the SWM (av. 1187 ± 1055 Ind. m−3 and av. 169 ± 119 Ind. m−3, respectively), probably a result of the DO deficient waters associated with upwelling. Two striking seasonal features in Copepoda community were evident in this study: (a) a compositional shift from Cyclopoida dominant during the NEM to Calanoida dominant during the SWM, and (b) the coastal OMZ along the Indian western shelf during the SWM was dominated by Calanoida, which include oceanic OMZ species such as Pleuromamma indica , Lucicutia flavicornis , L.paraclausii , Eucalanus elongatus , Subeucalanus pileatus , S.subcrassus , and Clausocalanus furcatus. This forms a clear imprint for the extension of the oceanic OMZ into nearshore waters during the SWM due to coastal upwelling. • Considered Copepoda as an indicator of coastal hypoxia along the Indian western shelf. • A compositional shift of Copepoda was evident during different seasons. • Many Copepoda of oceanic OMZ were found in the coastal hypoxic zones. • The study shows the biological continuity of the coastal and oceanic OMZ. [ABSTRACT FROM AUTHOR]

This study characterizes the spatio-temporal wave variability along Southwestern Nigerian coastal and shelf areas in the Gulf of Guinea. This is to provide further insight into the hydrodynamic factors that influence geomorphologic changes on the low-lying coast. Reanalysis wind-field datasets are employed to generate hourly wind forcing for an unstructured WAVEWATCH III model to simulate some bulk wave parameters. The model is validated against data from offshore buoys and satellite altimetry at selected locations near the coast. Results show that the waves have an annual average of significant wave height (H s), peak period (T p), and wind speed (u) of ∼0.5 m, 4.1 s, and 3.9 m/s, respectively. They exhibit seasonal spatial variability that is highest in the peak rainy season from July to September (Av. H s : 0.56–0.79 m; Av. T p : 4.68–5.18 s; Av. u : 4.30–5.22 m/s) and lowest in the early dry season from November to January (Av. H s : 0.26–0.34 m; Av. T p : 3.37–3.80 s; Av. u : 3.25–3.50 m/s). Also, the monthly averaged wave power varies from 0.2 to 2.8 kW/m annually. However, a maximum H s of 2.2 m that generated power of 9.4 kW/m for 11.1 s was recorded during the peak of the rainy season in August. Overall, waves with relatively low intensity, which can be classified as smooth to moderate, propagate from the southwest direction and decrease towards the coast. The higher H s and T p recorded during the peak of rainy and end of dry seasons are attributed to the influence of far-away swells. A comparative assessment indicates that the Barrier-Lagoon coast is highly controlled by waves, while the Mahin mud coast, which witnesses frequent flooding events that degrade its shoreline, has little wave influence. Thus, local subsidence that increases the relative sea level is suggested to be taking place at sections of the muddy coast. This information is crucial for the sustainable engineering design and management of low-lying coasts. • The SW Nigerian coastal and shelf area is characterized by smooth to moderate waves. • The waves exhibit seasonal variations that are strongest at the peak of rainy seasons. • The Barrier-Lagoon shelf has relatively stronger waves that can be harnessed. • Complex hydrodynamic interactions control geomorphological changes in the area. • Mahin coastal degradation is aggravated by alterations in local geomorphology. [ABSTRACT FROM AUTHOR]

The width of shelves and continental slopes of the East Siberian and Laptev seas affected the postglacial transgression. This dependence, in turn, is directly determined by the viscosity of mantle layers. Based on numerical simulations, the sea level on the East Siberian Sea coast was at higher altitudes than on the Laptev Sea 4–6 ky BP. The difference in the transgression rate could be explained by the hydroisostatic mechanism. [ABSTRACT FROM AUTHOR]

Site GNL Quintero 1 (GNLQ1), located on the central Chilean coast (32°S), remains the only submerged fini-Pleistocene landscape reported for the southeastern Pacific coast to date. This unique site is characterized by a high frequency and diversity of extinct terrestrial faunal remains supported within a fine-grained sedimentary matrix. Several studies have been performed on the faunal assemblage; however, the sedimentary environment in which the site was formed still remains unclear. In this work, stratigraphic, sedimentological and geochemical analyses conducted on two marine cores are combined with seismic data to determine the depositional conditions affecting the formation of this exceptional shallowly buried submerged landscape. Previous results indicated that site GNLQ1 formed, at least between 28 and 21 ka, in an aquifer-fed freshwater lagoon that developed on a fluvial plain. Here, we show a three-stage sedimentological evolution. In the first stage, a shallow restricted freshwater lagoon formed under relatively arid conditions. Subsequently, the lagoon expanded and deepened under the humid climatic conditions that affected central Chile during the Last Glacial Maximum (LGM). Finally, around 8.5-8 ka, the most recent post-glacial marine transgression (PMT) submerged the site, probably eroding the Late Pleistocene – Early Holocene part of the sequence. Currently, the site lies at ca. 13 m b.s.l. within the shoreface of present-day Quintero Bay, 650 m from the current shoreline. This enhanced understanding of GNLQ1's evolution offers a new perspective on resource availability on the coastal shelf of western South America during the Late Pleistocene, as well as highlighting the unexpected paleontological potential of this area and encouraging future archaeological research of potential prehistoric evidence within these drowned landscapes. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to quantitatively examine the characteristics of suspended sediment on synthetic aperture radar (SAR) observations of sea roughness. In this work, seven Sentinel-1 (S-1) SAR images in 2019 acquired in the Interferometric Wide-swath (IW) mode at vertical-vertical (VV) polarization channel were collected, where Yangtze River freshwater dominants and suspended sediment concentration (SSC) are higher in continental shelf of East China Sea (ECS). These images were collocated with waves simulated from WAVEWATCH-III (WW3) and SSC inverted from the Haiyang-1C (HY-1C) Coastal Zone Imager (CZI) image. The comparison of WW3-simulated SWH yielded a 0.45-m root-mean-square error (RMSE) with a 0.78 correlation (COR) when comparing the simulations with the measurements from Haiyang-2B (HY-2B). The SAR-measured normalized radar cross-section (NRCS) is linearly related with the HY-1 C SSC at SSC > 1200 mg l–1, which is caused by the change of dielectric constant of sea water and viscosity. Moreover, the NRCS is simulated by the three-scale radar backscattering model. It is generally found that HY-1 C SSC enhances the NRCS in difference between simulations and observations up to 8 dB at SSC of 2000 mg l–1, which could distort the accuracy of SAR wind retrieval. [ABSTRACT FROM AUTHOR]

Arctic river deltas and deltaic near-shore zones represent important land-ocean transition zones influencing sediment dynamics and nutrient fluxes from permafrost-affected terrestrial ecosystems into the coastal Arctic Ocean. To accurately model fluvial carbon and freshwater export from rapidly changing river catchments, as well assessing impacts of future change on the Arctic shelf and coastal ecosystems, we need to understand the sea floor characteristics and topographic variety of the coastal zones. To date, digital bathymetrical data from the poorly accessible, shallow and large areas of the eastern Siberian Arctic shelves are sparse. We have digitized bathymetrical information for nearly 75,000 locations from large-scale current and historical nautical maps of the Lena Delta and the Kolyma Gulf Region in Northeast Siberia. We present the first detailed and seamless digital models of coastal zone bathymetry for both delta/gulf regions. We validated the resulting bathymetry layers using a combination of our own water depth measurements and a collection of available depth measurements, which showed a strong correlation (r > 0.9). Our bathymetrical models will serve as an input for a high-resolution coupled hydrodynamic-ecosystem model to better quantify fluvial and coastal carbon fluxes to the Arctic Ocean but may be useful for a range of other studies related to Arctic delta and near-shore dynamics such as modelling of submarine permafrost, near-shore sea ice, or shelf sediment transport. The new digital high-resolution bathymetry products are available on the PANGAEA data set repository (Fuchs et al. 2021a, b). Likewise the depth validation data is available on PANGAEA as well (Fuchs et al., 2021c). [ABSTRACT FROM AUTHOR]

Spatially damped continental shelf waves (CSWs) with diurnal tidal frequency outside Lofoten–Vesterålen in north-west Norway are studied theoretically for an idealized shelf topography. Wave damping is caused by the exchange of fluid on the shelf with an inner archipelago through a permeable coastline. This exchange is modelled by the application of a Robin condition at the coastal boundary. It is shown that CSWs with diurnal frequencies are possible in a small wave number range centred around zero group velocity. By calculating the nonlinear radiation stress components in the spatially damped CSWs, we find the time- and depth averaged Lagrangian mean drift current to second order along the coast. We show that the Lagrangian mean drift current is independent of the value of the damping coefficient, however small, as long as it is nonzero. This illustrates the singular behaviour of the Lagrangian wave drift problem for CSWs. [ABSTRACT FROM AUTHOR]

Costa Rica has been affected by several local and distant tsunamis in the past, but the historical information is scarce and incomplete. Its Pacific coast stretches for over a thousand kilometers, and tsunami hazard has never been evaluated for its full extent. Numerical modeling of tsunami propagation and inundation is a useful tool to assess tsunami hazard, particularly in cases with limited historical information available. Here, we perform a first estimation of tsunami hazard for the Pacific coast of Costa Rica from seismogenic sources, by numerical propagation of 57 local and distant tsunamis to a depth of 20 m. The results of our study identified tsunami sources that are particularly threatening for Costa Rica and determined locations with higher tsunami hazard. For the analysis, the Pacific coast of Costa Rica was divided into segments and subsegments based on differences in continental slope morphology. Subsegments with higher tsunami heights were Southwest Nicoya Peninsula and West Osa Peninsula, and in a lesser extent North Guanacaste, North Nicoya Peninsula, and Central Pacific. Regions with long and gentle slopes and narrow continental shelf were affected by higher tsunami waves, due to more efficient tsunami energy transmission to the shelf and reduced energy loss while traveling through a narrow shelf. On the opposite, steeper continental slopes reflected most of the tsunami energy, causing smaller tsunami heights nearshore, regardless of the shelf width. Nevertheless, other effects played a major role, like curved coastlines that focused tsunami energy, wave refraction, interference, and trapped edge waves. Distant tsunamis dominated the threat, with tsunamis coming from the Tonga-Kermadec and the Colombia-Ecuador Trenches causing the greatest heights due to directivity, and arrival times of about 15 h and 75 min, respectively. Local tsunamis had short arrival times but a localized impact, mainly at the shoreline in front of the generation region but were also affected by tsunami focusing, wave refraction, and edge waves. Outer rise and Osa sources caused the lowest impact within local sources. These results provide a guide for emergency planners to prioritize coastal locations and tsunami sources for tsunami preparedness actions and warning protocols. [ABSTRACT FROM AUTHOR]

This paper presents a geomorphological map of the seafloor north east of the Maltese Islands (Central Mediterranean) at a scale of 1:50,000. The map was compiled following the integration, analysis and interpretation of several high-resolution seafloor bathymetry datasets. Several structural features, coastal and marine landforms and anthropogenic features have been mapped. Most of the mapped submerged landforms - including fluvial, gravity-induced and karst landforms - appear to have been formed during the sea-level lowstand of the last glacial cycle. The map provides valuable insights on the submerged landscape of the Maltese Islands and its evolution since the Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

The European eel hatches in the Sargasso Sea and migrates across the Atlantic Ocean toward Europe. At the continental shelf, larvae metamorphose into glass eels and then recruit to coastal habitats and estuaries. Among other cues, glass eels orient in situ using lunar cues, but what role this lunar compass plays in their recruitment to the coast is unknown. To assess this, we incorporated empirical in situ observations of glass eel swimming and lunar‐driven orientation into a biophysical advection model. We simulated dispersal of glass eels drifting with the North Atlantic Current to test the hypothesis that lunar‐driven swimming and orientation behavior affects recruitment to North Sea coasts. Particles were released from the continental slope north of Scotland, an obligate passage for migrating eel larvae. Four numerical experiments were conducted: one with passive drift and three including glass eel swimming speeds (ranging from 3 to 12 cm/s) and lunar‐driven orientation. With a speed of 3 cm/s, the lunar compass increased recruitment to the North Sea coasts of Southwestern Norway and Scotland by 34%–40%. Conversely, orientation behavior decreased recruitment to northern areas like Iceland (−46%), the Faroe Islands (−39%) and Northern Norway (−49%). Behavior affected the timing of recruitment to Southwestern Norway, causing peaks of abundance in May–June, but not to other regions. These results show that lunar‐driven orientation and swimming behavior observed in glass eels substantially increases their recruitment to North Sea coasts. Results agree with the distribution of eel in northern Europe, which decreases in abundance with increasing latitude. [ABSTRACT FROM AUTHOR]

For most of the period of human occupation of Sahul (the combined Pleistocene landmass of Australia and New Guinea), lower sea levels exposed an extensive area of the northwest of the Australian continent, connecting the Kimberley and Arnhem Land into one vast area. Our analysis of high-resolution bathymetric data shows this now-drowned region existed as an extensive archipelago in Marine Isotope Stage 4, transforming in Marine Isotope Stage 2 into a fully exposed shelf containing an inland sea adjacent to a large freshwater lake. These were encircled by deep gorges and escarpments that likely acted as important resource zones and refugia for human populations at that time. Demographic modelling shows the shelf had a fluctuating potential carrying capacity through Marine Isotope Stages 4–2, with the capability to support 50–500 k people at various times. Two periods of rapid global sea level rise at 14.5–14.1 ka (Meltwater Pulse 1A), and between 12 ka and 9 ka, resulted in the rapid drowning of ∼50% of the Northwest Shelf. This likely caused a retreat of human populations, registering as peaks in occupational intensity at archaeological sites. We contend that the presence of an extensive archipelago on the Northwest Shelf in Marine Isotope Stage 4 facilitated the successful dispersal of the first maritime explorers from Wallacea, creating a familiar environment for their maritime economies to adapt to the vast terrestrial continent of Sahul. • MIS4 lowstand exposed a vast archipelago off the northwest coast of Sahul. • The island environment likely enabled staged human dispersal from Wallacea to Sahul. • The NW Shelf contained a mosaic of habitable fresh and saltwater environments. • Modelling reveals the drowned shelf could have supported between 50,000 and 500,000 people. • Retreat ahead of sea level rise drove increasing occupation and new rock art styles. [ABSTRACT FROM AUTHOR]

• The residual sediments were concentrated in the central of the Malacca Strait, while the modern terrigenous sediments were distributed along the coastal side. • The sedimentary environment in the Malacca Strait presented residual, reworked, and modern characteristics. • The sedimentary dynamics restricted the transport of modern terrigenous sediments from the coast to the central region of the Malacca Strait. The Malacca Strait is not only a part of shelf deposition but also a crucial conduit connecting the continental shelf to the deep ocean. Here, we present the grain size characteristics of sediments in the Malacca Strait and regional hydrographic data obtained from global models to delineate its depositional configurations and further identify its sedimentary environments. The results reveal that the residual sediments are concentrated in the central region of the strait, whereas the modern terrigenous sediments are distributed along the coast of Malaysia and the broad northern region of the strait. The central region of MS, ProvinceⅠ, has the coarsest sediments with moderate sorting, indicating a residual sedimentary environment where the sands are residual paleo-river deposits. There are poorly sorted silty sands in ProvinceⅡ, which display finer mean grain size than that of ProvinceⅠ. It suggests a reworked sedimentary environment with variations of sediment sources between the southern and northern regions. It is a palimpsest of the paleo-deltaic deposits in the southern region, which have been intensely altered by modern high-energy hydrodynamic conditions. In terms of the northern part of ProvinceⅡ, it has modern reworked deposits shaped by wave, tide, and monsoon currents. The finer sediments, which correspond to the distribution of higher silt content, are supplied by the surrounding land in ProvinceⅢ indicating a modern environment primarily influenced by seasonally varying sedimentary dynamics, such as monsoon currents, well-developed eddies, and water masses. We thus propose that the depositional configurations in the Malacca Strait are confined by depositional dynamic environments, which restrict modern terrigenous sediments distributed along the coast and scarcely transported into the central region of the strait which exposes residual deposits. This study highlights the importance of both modern and relict sediments in the strait and our findings are important to better understanding modern strait sedimentary systems with high tidal-current-energy. [ABSTRACT FROM AUTHOR]

Antecedent conditions and geology influence bedform dynamics and other sea-bed bottom current interactions on the continental shelf. However, the nature of this influence has not been well constrained, particularly on current-swept shelves. A variety of bedforms (narrow and broad sediment ribbons, comet marks and subaqueous dunes) are revealed by high resolution multibeam bathymetry and side scan sonar surveys of the mid-to outer "Wild Coast" shelf along the east coast of South Africa. The bedforms demonstrate a relationship to the geological framework of the shelf. The various bedforms occur in conjunction with bedrock-incised valleys and topographic depressions filled with transgressive sediment and bounded laterally by prominent rocky outcrops. These sediment sources are siphoned and mobilised by the Agulhas Current to create the contemporary shelf bedforms. Mechanisms of bedform development are associated with the interplay between the loci of sediment supply and associated grain size on the one hand and the current velocity and pathway of the Agulhas Current on the other. Sediment ribbons form parallel to the flow path of the Agulhas Current in narrow or broad forms that can be differentiated primarily by sediment grain size. With increased sediment availability from nearby bedrock-bound depocenters these transition along shelf to 2D dunes. A cross-shelf transition to 3D dunes on the outer shelf is marked by increased current velocity, grain size and decreased sediment availability outside of rock-bound depocenters. Rock outcrops affect current velocity and flow paths sufficiently to favour localised deposition over sediment stripping from the shelf. Comet mark forms develop from interactions between availability of finer sediment and perturbations of current flow paths by rock outcrops. This creates conditions that favour localised sediment scouring over deposition. With variability in sediment size, grain size and current flow, dunes fluctuate between active (sharp crested), inert (round crested) and degraded (flat crested) states. A lack of available sediment to replenish outer shelf dunes sees prolonged stasis, eventual dune splitting and breakdown under progressive current influence. Mid-shelf dunes have a greater capacity to recover from periods of stasis and short-term degradation due to greater availability of sediment. Dune migration rates are slower than previous regional estimates. Reasons for this are inconclusive and may be multifaceted. Possible reasons include inertial constraints, prolonged downcurrent reformation periods and longer dune relaxation associated with coarser grain sizes and a paucity of sediment on the outer shelf coupled with the Agulhas Current core migrating further in and offshore. This may explain the stability of the large barchan dunes and reduced movement of other sharp crested dunes relative to the regional migration rates. • Document sediment dynamics on a geostrophic-current dominated shelf. • Reveal influence of geological control on dune development. • Core of Agulhas Current directed by changes in shelf physiology. [ABSTRACT FROM AUTHOR]

The landings of the artisanal elasmobranch fisheries of 3 communities located along the Pacific coast of Guatemala from May 2017 through March 2020 were evaluated. Twenty-one elasmobranch species were identified in this study. Bottom longlines used for multispecific fishing captured ray species and represented 59% of the fishing effort. Gill nets captured small shark species and represented 41% of the fishing effort. The most frequently caught species were the longtail stingray (Hypanus longus), scalloped hammerhead (Sphyrna lewini), and Pacific sharpnose shark (Rhizoprionodon longurio), accounting for 47.88%, 33.26%, and 7.97% of landings during the monitoring period, respectively. The landings were mainly neonates and juveniles. Our findings indicate the presence of nursery areas on the continental shelf off Guatemala. This study included the first survey of commercial exploitation of ray species in the artisanal fisheries off the Pacific coast of Guatemala. It is imperative to protect shark nursery areas and to develop management strategies for ray species that are important to artisanal fisheries. [ABSTRACT FROM AUTHOR]

This article examines the development of case law concerning the criteria determining the relevant coasts and the relevant areas in delimitation of the exclusive economic zone and continental shelf. There is a discrepancy in the jurisprudence over whether the relevant area is determined by assessing the overlaps of "seaward extension," "projections," or "potential entitlement," and this undermines the transparency of the process and the predictability of the result. There is also a debate over whether identification of the relevant area shall be based on "frontal" or "radial" projections. This article tracks this jurisprudence, questions why there is a discrepancy, and critically analyzes the consequences of these decisions in the light of the principle of equity. [ABSTRACT FROM AUTHOR]

Bagnoli-Coroglio is a Site of National Interest (SNI) facing the Pozzuoli Bay that has been the place of an industrial activity for more than a century (1854-1985). The modern coastal geology of this area results from the recent evolution of an antecedent volcanic landscape that originated after a caldera collapse following the eruption of Neapolitan Yellow Tuff (NYT) of Campi Flegrei (15 ka). After the NYT eruption, a shallow marine depression formed within the caldera collapse area that underwent progressive filling-up, due to volcaniclastic sediment input from the caldera borders, within a semi-enclosed source-to-sink system. The integrated interpretation of the Digital Terrain Model (DTM) of the Bagnoli-Coroglio area and the high resolution reflection seismic profiles acquired off the Pozzuoli Bay suggests that the present-day coastal plain of Bagnoli-Fuorigrotta and conterminous continental shelf represent the latest infilling phase of the annular depression (caldera 'collar') between the structural border of the NYT caldera and the inner caldera resurgent dome. The stratigraphic architecture and morpho-bathymetry of the Bagnoli inner shelf provide a record of the complex interplay between eustatic sea level changes, volcano-tectonic (ground/seafloor) deformation, and supply of volcaniclastic sediments, with associated coastline shifts over the last millennia. [ABSTRACT FROM AUTHOR]

The paper discusses the principles of developing a hierarchical system of units for zoning the coastal zone and shelf of the World Ocean based on bionomic (ecosystem) features are discussed. A number of scientific and applied problems require zoning of ecoregions (sea basins) at the regional and topological levels. A system of units is proposed, taking into account the zonal, depth-related, and azonal features of ecoregions. The main initial unit of bionomic zoning is the underwater landscape. As an example of regional and topological zoning, the morphological structure of landscapes of three districts of the Japanese coastal region of the Sakhalin orogenic region of the Japan Sea is considered. The hierarchical system of units of bionomic zoning makes it possible to identify landscape analogues. In practical terms, this zoning may help to predict the introduction of useful species and forecast the risk of invasion by harmful species. [ABSTRACT FROM AUTHOR]

Since the 1970s, analytical models of coastal trapped waves (CTWs) have been developed using a first-order wave equation in the long-wave limit. Formulations of this kind require assumptions of a straight coastline with similar shelf bathymetry. These assumptions prevent the models from capturing the scattering and backscattering behavior of propagating CTWs that encounter changing coastlines, bathymetry, or shelf width. CTW modes from two different analytical models, one of which includes friction and stratification, are compared with CTW observations of velocity and pressure from a study region near the Outer Banks off the North Carolina coast in the United States. The coastline in the study region is relatively straight locally but is bounded by an estuary to the north and shelf narrowing to the south, both of which induce scattering. The models suggest that the CTWs in this region are insensitive to changes in stratification, implying that observed seasonal differences in wave magnitude are due to seasonal wind forcing. Furthermore, friction is found to be important, particularly for mode-1 propagation, but higher-order modes are prevalent despite the importance of friction. There is very poor agreement between the observed and modeled free and forced CTWs because of scattering. This lack of agreement indicates that this is not a globally applicable theoretical formulation because many global coastlines violate the basic assumptions. [ABSTRACT FROM AUTHOR]

Sediment source-to-sink processes of river systems have significant impacts on depositional environments in coastal and shelf seas and on long-term climate change. Typically, sediments at the outlets of small mountainous rivers (SMRs) are considered to represent the average composition of particles eroded from the entire river basin due to the fast sediment transfer rate and short residence time in the basins. However, this assumption may be challenged by the significant heterogeneity in sediment erosion and transport processes within the SMRs catchments. In this study, we compare the geochemical and provenance heterogeneity of two typical mountainous rivers in subtropical East Asia, the Mulanxi in Mainland China and the Zhuoshuixi in Taiwan. These two SMRs have similar monsoon climate regimes but different tectonic, geomorphic, and hydrological settings, as well as sediment routing processes. Neodymium isotopes (εNd) and stable elemental ratios of Cr/Th and Sc/Th demonstrate the remarkable intra-catchment geochemical heterogeneity of both rivers. The εNd decreases from −7.1 to −10.0 from non-tidal to tidal reaches in the Mulanxi, while it changes from −11.5 in the upper reaches to −14.1 in the lower reaches of Zhuoshuixi. Apart from the general controls of provenance lithology and weathering processes on sediment geochemical heterogeneities between these two SMRs, the intra-catchment heterogeneity of the Zhuoshuixi is mainly induced by uneven sediment mixing in the flat and low connectivity areas (accounting for ∼36.5% of the downstream area). Meanwhile, the strong tidal influence is the primary control for the intra-catchment geochemical heterogeneity of the Mulanxi sediment, and relatively long sediment residence time in the catchment also plays some role. Our study suggests that samples collected at the river mouths cannot be simply treated as representative of the basin average or fluvial end-member to the sea. The compositional heterogeneity of the SMRs and its environmental effects and responses to rapid climate change require more in-depth investigations. • Distinct geochemical heterogeneity observed between SMRs in subtropical East Asia • Tide-induced sediment mixing accounts for heterogeneity of SMRs in SE China coast • Geomorphic features and climate events explain the heterogeneity of Taiwan rivers • Samples in the river mouth cannot represent the fluvial end-member to the sea [ABSTRACT FROM AUTHOR]

The Kuroshio Current carries a large amount of nutrients in dark subsurface layer along the southern coast of Japan. However, due to lack of sufficient multidisciplinary high‐resolution observations, it has been unclear whether and how the subsurface nutrients are injected to sunlit layers on the continental shelf. In this study, using a state‐of‐the‐art tow‐yo microstructure profiler and nitrate measurements, we show that the Kuroshio flowing on the shelfbreak induces very strong turbulent dissipation rate ∼O(10−7W·kg−1) and diffusivity ∼O(10−3 m2·s−1) over an across frontal scale of 20–30 km. This strong turbulence could provide a diffusive nitrate flux to euphotic zone of >O(1 mmol N·m−2·day−1). As the Kuroshio steadily runs on the continental shelves along the path, the nutrient injection found in this study is a very important supply for biological production on the continental margin along the southern coast of Japan. Key Points: Very strong turbulence is observed in the Kuroshio Current near shelfbreak over 30 km in the across frontal directionTurbulence is caused by banded internal wave shear amplified between the Kuroshio Current and the continental slopeTurbulent mixing causes a large diapycnal diffusive nitrate flux to the euphotic zone over 30 km [ABSTRACT FROM AUTHOR]

The northern of Chile is one of the most productive and permanent upwelling systems of the large Humboldt Current System. However, do not investigations have been developed about the decapod larvae dynamics in this region, characterized by its narrow continental shelf and an oxygen minimal zone (OMZ) very shallow (<50 m). Four oceanographic campaigns carried out in a coastal upwelling zone off northern Chile in 2003 were used to analyze the dispersal patterns of 15 taxa from decapods larvae selected. The coastal upwelling conditions showed a maximum Ekman transport value (Mx) in January and a minimum in May, while the temperature and salinity characteristics defined four types of waters named a) cold upwelling waters (UW), b) warm trapped waters (WTW), c) upwelling front waters (UFW) and d) oceanic front waters (OFW), which showed different concentrations of dissolved oxygen, OMZ depth (<1 mL L−1) and chlorophyll-a concentrations, respectively. Decapod larvae with the highest abundance and frequency were Cancer spp., Emerita analoga , Pinnaxodes chilensis , Callianassidae sp., Pagurus sp. and Allopetrolisthes sp., from adults of diverse habitats, characterized by different development stages and periods. The offshore weighted distance (Ğ) estimated for the decapod larvae allowed the differentiation of three main groups. a) group formed by high dispersion larvae (>11 km), with five zoea stages and associated to the UFW waters, b) group formed by mean dispersion larvae (between 5 and 8 km) and distributed in upwelling waters (UW), and c) group showing lower horizontal dispersions (<4 km), which significantly and negatively correlated to the OMZ in UW and WTW-type waters. The different cross-shelf distribution patterns relative to the oceanographic conditions were compared with other upwelling system, and larval behavior, morphology, environmental requirements and development period of different decapods were discussed. • Horizontal dispersion of decapod larvae are similar in different upwelling systems. • Ekman transport does not act similarly upon the dispersion potentials larvae. • Shallow minimum oxygen zone could affect the dispersion patterns decapod larvae. • Benthic decapods of the inner shelf zone have at least three dispersive strategies. [ABSTRACT FROM AUTHOR]

High-resolution shallow seismic investigations on inner continental shelf of Goa have been carried out to map gas-charged sediment zones and investigate origin of trapped gas. Analyses of data reveal that the gas is trapped by different stratigraphic layers and is distributed in two zones. Zone-1 is restricted up to ~30 m water depth and in the southern part of the study area. In this zone, gas is confined within the Holocene layers above the Holocene maximum Hooding surface (MFS). Whereas, zone-2 is comprised of several isolated gas-charged patches which are distributed in the entire study area mostly between ~20 m and ~45 m water depth. In this zone, gas is confined below Holocene- MFS in incised river bed or a layer just below MFS or both. Gas-charged sediment in zone-1 is formed due to degradation of organic material which is predominantly early Holocene mangrove derived, whereas, zone-2 it is formed due to degradation of organic material which were deposited by ancestral rivers during the post-glacial sea level rise of the Late Pleistocene. The distribution pattern of zone-1 is controlled by coastline configuration, long-term longshore current pattern, Holocene rapid sea level rise and lithological character of exposed inter-tidal zone. Whereas, distribution of zone-2 is controlled by palaeo-rivers of different glacial periods and their hydraulic energy condition during the base level rise. [ABSTRACT FROM AUTHOR]

Abstract Continental shelf sediments are a major source of iron (Fe) for phytoplankton in surface waters. In this study, we investigate the mechanisms that control release of Fe from shelf sediments and its lateral transport ("shuttling") in oxic and hypoxic waters on the northwestern Black Sea shelf. We find that at two coastal stations near the outflow of the Danube river high input of organic matter drives strong reductive dissolution of Fe(oxyhydr)oxides (henceforth termed Fe oxides) in surface sediments, supporting high rates of Fe release to oxygenated bottom waters (∼0.36 mmol m−2 d−1). We suggest that bioirrigation plays a key role in the release of Fe from these sediments. At four stations further offshore organic matter deposition is lower resulting in limited mobilization of Fe2+ in the sediment and low benthic fluxes of Fe (<0.07 mmol m−2 d−1). Lateral transport of Fe from the coastal zone towards the deep basin mostly takes place in colloidal and/or particulate form (>0.2 μm) in the lower part of the water column, likely through repeated deposition and resuspension of Fe oxides from surface sediments. Using synchrotron-based X-ray spectroscopy and sequential chemical extractions, we demonstrate that the suspended matter and surface sediments are enriched in easily reducible Fe oxides (mostly ferrihydrite) and Fe associated with clay. The mobilization of Fe in the coastal zone and subsequent lateral transport of these Fe-bearing particles results in higher ratios of Fe/Al in surface sediments at outer shelf stations (ca. 1.2 to 2 wt.% wt.%−1) than at coastal stations (ca. 0.5 to 0.9 wt.% wt.%−1). However, below the sediment surface layer Fe/Al ratios are similar at all stations indicating limited burial of the laterally transported Fe. Our results highlight the critical role of organic matter input, associated biological activity and riverine Fe input as drivers of Fe shuttling on continental shelves. We also show that in shelf areas where sediments receive low inputs of organic matter, physical transport controls the ultimate fate of the shuttled Fe. This article is part of a special issue entitled: "Cycles of trace elements and isotopes in the ocean - GEOTRACES and beyond" - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González. Highlights • On the northwestern Black Sea shelf, iron is released from coastal organic-rich sediments overlain by oxic bottom waters. • Bioirrigation is suggested to play a key role in the release of iron from coastal sediments. • Transport of iron over the shelf takes place through repeated deposition and resuspension. • Most iron is transported in the lower part of the water column as ferrihydrite and iron associated with clay. [ABSTRACT FROM AUTHOR]

Mechanisms in controlling the growth of heterotrophic bacteria have seldom been explored in the tropical South China Sea (SCS). This study reports the tempospatial distribution patterns and the controlling mechanisms of bacterial biomass (BB), production (BP), and specific growth rate (Bμ) from one summer (Jun 2010; 4 transects) and two winter (January and December 2011; one transect each) cruises along the northern SCS-shelf. In summer, all three bacterial variables showed strong gradients with greater readings at the inner-shelf then decreasing seaward. The positive correlations of bacterial production rate (BP) and bacterial specific growth rate (Bμ), with primary production (PP), chlorophyll-a, and dissolved organic carbon observed in summer indicate a high possibility of bottom-up (substrate supply) control. Positive bacterial temperature response was observed in the inner to mid-shelf area in winter. There, Bμ changed proportionally with temperature up to ca. 22°C. The Q10 (the increase of reaction rate for a temperature rise of 10°C) for Bμ was ~4.0, which was in the range reported by coastal studies. Very high BP/PP ratios (summer average: 89 ± 92%; winter average: 131 ± 88%) indicated bacteria carbon demand relied heavily on allochthonous organic carbon sources such as river input and re-suspension processes, and that the SCS-shelf might be net heterotrophic in these two seasons. In winter, BP/PP ratios changed positively with temperature in areas inside the midshelf, suggesting that the coastal zone might become a stronger CO2 source during cold season under a warming climate, if anthropogenic loadings of inorganic nutrients and organic matter remain high in the future. [ABSTRACT FROM AUTHOR]

Jardim, K.A.; Santos, V.F., and Oliveira, U.R., 2018. Paleodrainage systems and connections to the southern lacustrine belt applying remote sensing data, Amazon coast, Brazil. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 671–675. Coconut Creek (Florida), ISSN 0749-0208. Paleodrainage systems mapped in many regions worldwide reveal important inactive fluvial systems that indicate changes in morphosedimentary, tectonic and environmental processes in different time scales. Two paleodrainage systems were identified north of the Amazon River mouth, associated with the Southern Lacustrine Belt at Cabo Norte. The analyses were performed using data from orbital remote sensors, validated by field information and overflights. The paleodrainage systems show predominant North-South (N-S) and Southwest-Northeast (SW-NE) directions. The N-S system may be connected to an ancient Pleistocene coastline. The SW-NE system is younger, with the same direction as the current river courses and is associated with the genesis of the Araguari River. The paleodrainage alignments of this system in the Northwest-Southeast direction (NW-SE) show the same direction as tectonic lineaments presented from the basement to the continental shelf. The identified paleodrainage systems indicate significant changes in the regional drainage of the Amazonian coastal plain and indicate intense riverbed aggradation processes, which may be associated with neotectonic movements and relative sea level variations during the Quaternary. These are important indicators for the understanding of environmental changes during the Late Pleistocene and Holocene, and may aid in the paleogeographic reconstitution of the Amazon river mouth. [ABSTRACT FROM AUTHOR]

The marine environments off the Kimberley coast are being subjected to ever increasing human-induced pressures, with little known of the region's marine biodiversity, and therefore, which conservation approaches are appropriate. Consequently, the Western Australian Museum with partner agencies undertook to survey the region over a six year period (2009-2014). Thirty eight locations involving 179 survey stations were visited within the defined Project Area, which ranged from the Kimberley coast to the continental shelf edge. Geomorphic data from these stations, along with additional data from a 2006 survey, were incorporated into the analyses, providing a total of 224 survey stations. Analyses revealed a three-way differentiation of the surveyed stations demonstrating continental shelf zonation, an intertidal and subtidal distinction and a turbidity gradation. [ABSTRACT FROM AUTHOR]

Paleoamerican colonization models have emphasized the importance of coastal zones for provisioning hunter gatherers with a diverse range of subsistence resources. This article expands on recent research by Lowery et al. 2012, and presents a model to explain the distribution of Clovis points across the Atlantic slope of Eastern North America. Marine transgression since the last glaciation has submerged large tracts of the Atlantic continental shelf. Global bathymetric data was used to estimate the Clovis age shoreline from Delaware to Florida. Clovis biface data for modern coastal areas, obtained from the Paleoindian database of the Americas, was compared to the slope of the paleo-shoreline to predict coastal zone preference. Results indicate a relationship between point distribution and coastal zone type. Areas where major rivers with high-quality tool-stone intersect broad coastal zones served important roles to Clovis subsistence adaptations. The potential exists for early Paleoamerican sites along the continental shelf submerged beneath 55–75 m of the Atlantic Ocean. Modern coastal regions with high densities of Clovis points may serve as analogues for identifying earlier sites that have been submerged as a result of marine transgression. [ABSTRACT FROM PUBLISHER]

The ecosystems of the Israeli Mediterranean coast have undergone significant changes in recent decades mainly due to species invasions and fishing. In order to characterize the structure and functioning of the marine continental shelf of the Israeli Mediterranean coast and assess temporal changes, we developed a food web model representing two time periods: 1990–1994 and 2008–2012. The 1990–1994 and 2008–2012 food web models were composed of 39 and 41 functional groups, respectively. Functional groups ranged from primary producers to top predators, and included six and eight alien functional groups, respectively, encompassing several crustacean and fish species. Input data included local surveys and fishery statistics, published data on stomach content analyses, and the application of empirical equations to estimate consumption and production rates. Results of the competitive interactions between alien and native species and changes in trophic flows between food web components highlight the increasing impact of alien species over time. Fishing had noticeable impacts in both time periods and played an important role in the ecosystem. Despite different productivity rates and other environmental differences, the Israeli marine ecosystem shared common structural and functional traits with other Mediterranean marine ecosystems. This is the first attempt to study the ecosystem of the Levant region using mass-balance models and to integrate such a large amount of alien species into food web analyses. [ABSTRACT FROM AUTHOR]

Offshore wind farms typically host tens to hundreds of turbines that are individually sited on foundations or anchored if floating. These turbines are connected by inter-farm cables which feed into one or more marine-based substations, further feeding one or more shore-connected high-voltage cables--all infrastructure that requires knowledge of water depth, metocean conditions, and seabed/subsurface geology. With this industry set to establish itself on the continental shelf of Atlantic Canada, knowledge of the geological conditions from the seabed to tens of metres below will be essential for farm layout and foundation design. Thus, geoscience questions addressing regional geomorphology, Pleistocene glacial retreat and sea-level change, the characteristics of key individual stratigraphic layers, and the magnitude and patterns of sediment mobility are important. In Atlantic Canada, ongoing efforts to address these questions are using legacy data, but new data is required to further our understanding of the shallower portions of the shelf. Examples include: what is the distribution of buried tunnel valleys under offshore banks, and might their complex facies infill affect foundation conditions? How and where would the organic sediments, left by a coastal suite of landforms drowned during transgression, affect foundation or landfalling cable stability? How active is salt diapirism, and could it be considered a geohazard? Are demonstrated sediment mass failures also a risk? What is the current understanding of sediment mobility in shallow waters, and how does that affect infrastructure armouring/depth of burial? What is the variability of the geotechnical properties of our offshore sediments? What is the foundation suitability of offshore Tertiary semi-consolidated bedrock? To conclude, the initial scope of a developing regional foundation suitability model will be presented for the Eastern Scotian Shelf. [ABSTRACT FROM AUTHOR]

The composition and distribution of macrobenthic communities was investigated in three areas in the KwaZulu- Natal Bight, a section of shelf off the east coast of South Africa. Areas were pre-selected on the basis of three known oceanographic features, posited to deliver land- or Agulhas Current-derived nutrients onto the shelf and to drive ecosystem functioning in this region. Replicate sediment samples were collected with a 0.2 m2 van Veen grab, during two surveys (A, B) corresponding with normal periods of high and low rainfall, respectively. A subset of the full station array was selected across the shelf in an arrangement of increasing depths (inner-, mid- and outer shelf) through each feature area to investigate the spatial distribution and feeding modes of macrobenthic taxa. The two periods showed some differences in abundance and numbers of macrobenthic taxa, but were not statistically different. Total macrobenthic abundance from Survey A was 20 215 individuals from 642 taxa, decreasing to 18 000 individuals from 503 taxa during Survey B. Polychaeta and Crustacea were the dominant taxa sampled; abundance of the latter was attributed largely to a proliferation of Paguristes sp.1 at inner-shelf samples in the midbight (Thukela) region during Survey B. Similarity classification distinguished seven sample groups reflecting differences in feature areas and shelf positions under investigation. The Thukela River midshelf community supported the highest macrobenthic abundance, while the midshelf off the southern bight (Durban region) was most species rich. Findings were attributed to the habitat complexity of the midshelf which includes a palaeo-dune cordon at the 60 m isobath. Functionally, the community was dominated by interface- and deposit-feeding fauna, emphasising the importance of trophic plasticity in an environmentally variable and heterogeneous shelf environment. [ABSTRACT FROM AUTHOR]

Transport and accumulation of radionuclides in the Arctic depends on many biogeochemical processes, which are changing at accelerated rates due to climate change and human economic activity. We present the results of a study on the features distribution of some natural radionuclides in the marine sediments on the East Siberian Arctic Shelf collected during several expeditions from 2008 to 2019. Average activity concentration of 232Th, 40K and 226Ra under the influence of different sedimentation regime increases from 40.7, 418 and 30.8 Bq/kg to 41.6, 423 and 34.9 Bq/kg respectively from coastal shelf marine sediments (<50% clay) to outer shelf marine sediments (>50% clay). Sediment particle size has a greater impact on radionuclides in the coastal shelf. An increase in the activity concentrations of 232Th and 226Ra with the increasing clay particles were found. On the outer shelf with a change in the sedimentation regime, the influence of the size composition decreased, at the same time, there is a correlation between the organic carbon concentration and the radionuclide activity concentration. Absolute maximums of natural radionuclide activity concentration (232Th = 70.9, 226Ra = 70.4, 40K = 591 Bq/kg) were detected in the Chaun Bay. The highest activity concentration of 226Ra was found in paleo-river valleys marine sediments. A low 232Th/226Ra activity concentration ratio indicates the enrichment of paleo-river valleys marine sediments with 226Ra. In the deep-sea sediments of the shelf slope on the contrary paleo-river valleys, this ratio is greatly increased. • The activity concentration of natural radionuclides increases from coast to outer ESAS. • Sediment particle size has a greater impact on radionuclides in the coastal ESAS. • On the outer ESAS, the influence of biogenic OM on radionuclides increases. • The highest activity concentration of 226Ra was found in paleo-river valleys marine sediments. [ABSTRACT FROM AUTHOR]

Output from a high-resolution ocean model, a wind reanalysis and a particle tracking tool are used to improve our understanding of the shelf circulation in an embayment off South Africa's east coast, known as the KwaZulu-Natal Bight. This region spans across roughly 140 km of coastline and is located between 29°S and 30°S. It is influenced by the strong, south-westward flowing Agulhas Current on its offshore edge, while its shelf is dominated by weak and variable currents. On the KwaZulu-Natal Bight's shelf, realistic high-resolution model simulations indicate the presence of a mean north-eastward flow: the Natal Bight Coastal Counter-Current. The mean surface circulation depicts a Natal Bight Coastal Counter Current stretching along the 50 m isobath from the southern to the northern section of the KwaZulu-Natal Bight while progressively becoming narrower and weaker northwards. The mean vertical structure of this counter current extends throughout the water column and at its origin, it almost connects with the Agulhas Undercurrent. In this region, the Natal Bight Coastal Counter-Current is about 20 km wide and has an average speed of 20 cm/s at its core, which may exceed 100 cm/s during individual events. The passage of southward propagating anticyclonic eddies offshore of the Agulhas Current are associated with a southward flow along the southern KwaZulu-Natal Bight region and the interruption of the otherwise north-eastward shelf currents. While the circulation in the KwaZulu-Natal Bight is primarily driven by perturbations at the Agulhas Current front, there is also some indication of a direct wind-driven influence in coastal waters, inshore of the 50 m isobath and north of 29.5°S. Virtual particle tracking experiments show that the Natal Bight Coastal Counter Current may increase connectivity between Marine Protected Areas within the KwaZulu-Natal Bight, where the current greatly increases the water retention. This may trap nutrients from coastal origins on the shelf, together with any suspended particles such as larvae. Therefore, the Natal Bight Coastal Counter-Current has the potential to increase the suitability of this habitat for larval settlement. • The model shows a mean north-eastward flow that extends across the length of the KwaZulu-Natal Bight. • The Natal Bight Coastal Counter-Current (NBC3) finds its origin in the Durban Eddy. • Offshore anticyclonic eddies interrupt the NBC3. • Winds are a strong driver of the coastal circulation inshore of the 50 m isobath. • The NBC3 impacts MPA connectivity. [ABSTRACT FROM AUTHOR]

This study assessed the influence of the seasonal fluctuation of abiotic conditions (wet v. dry season) on the functional diversity ( FD) of tropical coastal fish assemblages. Sampling was carried out in three regions of north-east Brazil with contrasting coastlines (influenced by reef, lagoon and estuary). In each region, fishes were sampled from three depth strata (10, 20 and 30 m) and FD was estimated using an index based on key phenotypic and behavioural characteristics. All three regions had higher FD in the wet season at shallower depths, indicating the coexistence of species with low functional redundancy in sites subject to seasonal flushing of fresh water. Deeper sites had lower FD than shallower sites, although this difference was less pronounced for region 3, which is strongly affected by its proximity to the São Francisco estuary. The results broadly support the hypothesis that alterations in abiotic conditions in the wet season allow estuarine-adapted fishes with a different suite of functional traits to invade shallow coastal regions. [ABSTRACT FROM AUTHOR]