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The morphological evolution of embayed beaches on a microtidal coast is assumed to largely respond to the degree of exposure to wave conditions, decreasing the mobility with increasing beach indentation (and vice versa). However, the number of sediment arrivals at the beach or the impact of extreme storms can modify this relationship. Here, we present an analysis of 10 embayed beaches along the Catalan coast with different morphometric and sedimentary characteristics to identify the most relevant parameters controlling the morphological evolution of these embayed beaches at the inter-annual and decadal scales. The study was mostly based on LiDAR topographic data collected from 2012 to 2017, aerial photographs from 1945 to 2021, sediment sampling and a long-term series analysis of the forcing parameters (waves, sea level, precipitation and land-use changes). The results show a net loss of volume on all the studied beaches at an inter-annual scale and a general shoreline retreat during the last few decades, suggesting the influence of common processes on the evolution of the studied beaches. Smaller pocket beaches with medium-to-high indentations are more sensitive to changes induced by local factors and show higher variability in the volume of the emerged beach and shoreline position than larger beaches. The most relevant factors influencing the evolution of the studied beaches on a decadal scale were identified as changes in sea level and the reduction in sediment inputs provided by streams due to land-use changes in the drainage basin. At the inter-annual scale, the impact of extreme events is the main factor controlling beach behaviour. These general trends can be opposite locally for beaches that receive large amounts of sediment via longshore transport from adjacent beaches

Maërl habitats are composed of coralline red algae species that can live freely rolling on the seabed and forming nodules, the so-called rhodoliths, or incrusted forming coralligenous habitats. Maërl habitats are generally distributed in the Mediterranean at a depth of between 30 m and 70 m and are considered one of the most emblematic Mediterranean seabeds. In the present study, the complex structure of maërl habitats was investigated to i) characterise the relief features and classify the different sediments, ii) to estimate the abundance of the coralline red algae (both rhodoliths and encrusting ones) and iii) to analyse the biodiversity of the species inhabiting the habitat. Data were obtained from an approximately 11 km-long transect, using non-intrusive sampling methods, integrating information from video images collected using the Remotely Operated Vehicle LIROPUS (IEO_CSIC), and multibeam bathymetry and backscatter data. Video images were used to reconstruct (using GIS) the habitat structure and characteristics. Throughout the transect, a strong relationship between habitat characteristics and the effect of trawling activity and the geomorphology of the studied area was observed. The closed area to fishing activity showed a high abundance of rhodoliths in well-structured megaripples reliefs. Contrarily, the areas affected by fishing showed an important destructuring of the relief with a low density of rhodoliths. Last, the muddy bottoms showed areas with no characteristic features and no rhodoliths. All this information has allowed to reconstruct the maërl habitat in the Blanes continental shelf (NW Mediterranean) and analyse the fragmentation of the assemblages seen in the video to assess its good environmental status (GES), and finally to identify the level of ecological integrity of this vulnerable habitat.

This research aims to distinguish genetic sedimentary processes building canyon geomorphological patterns and the factors driving different sedimentary activities in two nearby Mediterranean shelf-incised submarine canyons (Carchuna and Motril) that exhibit different degrees of incision on the narrow margin of the northern Alboran Sea. The straight Carchuna Canyon incises the shelf up to 200 m off the coastline and exhibit steep canyon walls featuring narrow terraces, muddy sands with high contents of organic matter along the thalweg, and transported shelf benthic foraminifera in distal settings. The Motril Canyon head is wider and incises the shelf edge, ca. 2 km off the coastline. It exhibits a sinuous morphology and less steep walls, wider terraces, and higher sedimentation rates with muddy sediments along the thalweg. In both canyons, cross-section relief, width, incision, and area decrease downslope, although these parameters increase locally. The downslope variations of geomorphological parameters are attributed to enhanced erosional/depositional processes promoted by tectonically controlled abrupt changes of the axial channel orientation. The degree of shelf incision, the location of the canyon heads in relation with the local sediment sources, and the seasonally variable hydrodynamic regimes determine the different degrees of recent canyon activity. The Motril Canyon is interpreted as a mature system that reflects episodic activity, collecting fine-grained sediments from the nearby Guadalfeo River. The Carchuna Canyon exhibits a youthful developmental stage whose activity is more continuous and involves sediment trapping of littoral cells and continuous downslope sand transport

The quantification of sediment exchanges between the beach and the lower shoreface, although being still poorly understood, is required to adequately forecast long-term coastal evolution. The effect of extreme storms on the morphodynamics of the nearshore and the sediment budget of the coastal zone seems to be strongly conditioned by local parameters, which should be incorporated into studies of medium- and long-term coastal evolution. In the upper shoreface, the dynamics of shore-parallel bars in sandy coasts have been extensively studied, but their implications for the sediment budget remain controversial as it is unclear whether their evolution simply represents a morphological change or denotes an escape of sediment from the upper shoreface. In order to provide new knowledge to address these questions, fifteen topo-bathymetric surveys that extend from the emerged beach to 15 m water depth were carried out along 1 km of Castelldefels beach (Llobregat Delta, Barcelona, western Mediterranean Sea) during the period 2011–2022. Morphological variations on the shoreface are studied, volumetric changes are estimated and implications on sedimentary exchanges in the littoral profile are inferred. The largest morphological (volumetric) changes are caused by cross-shore displacements of the nearshore bars, usually onshore during fair-weather conditions and offshore during storms. Volumetric changes suggest that shoreline retreat and the erosion of the shallow section of the profile during the last decade provides sediment to both the distal upper shoreface and the lower shoreface. The resulting sediment budget in the profile is almost zero in absence of extreme storms, but becomes highly negative when including extreme storms events that cause a net offshore transfer of sediment from the upper to the lower shoreface and, probably, the inner shelf. The characteristics of the study area (morphology, sediments, waves, tides) and in-situ hydrodynamic measurements at the lower s

Los fondos marinos siguen siendo grandes desconocidos. Frente a los paisajes terrestres, más accesibles y familiares, la mayor parte de ellos permanecen inexplorados, siendo un enorme desafío para la investigación científica. Este libro da a conocer los paisajes submarinos de distintas zonas del Mediterráneo peninsular: unos fondos singulares y poco explorados, formados por crinoideos (animales exclusivamente marinos) y maërl (agregaciones de algas marinas calcáreas), que se hallan entre los 20 y 200 metros de profundidad. De un gran interés ecológico por su rica biodiversidad de fauna y flora, son también fondos muy vulnerables, al estar sometidos a una intensa actividad pesquera y a distintas perturbaciones medioambientales, de ahí la necesidad y urgencia de su protección, y de lograr un equilibrio entre conservación y explotación. Imperativos que adquieren una mayor relevancia al tratarse de hábitats que son una abundante fuente de bienes y servicios, desde la provisión de alimento hasta la mitigación de los efectos del cambio climático, contribuyendo a la salud y bienestar planetarios y humanos. Escrita por un equipo de investigación multidisciplinar en ciencias del mar y gracias a las insólitas filmaciones captadas por el vehículo submarino ROV LIROPUS 2000, como parte de la Campaña Oceanográfica CriMa (ICM/CSIC), esta obra desvela las características y peculiaridades de estos ecosistemas marinos

[EN] Coastal erosion poses significant challenges for urban beaches and requires engineering solutions that combine the construction of protective structures with coastal regeneration measures. This study investigates the morphological evolution of an enclosed urban beach in the presence of submerged breakwaters and regeneration works, analysing their effect on the mitigation of coastal erosion and the restoration of the beach profile. Through an analysis of topo bathymetric campaigns, the temporal changes in the coastal morphology are evaluated in relation to the implementation of submerged breakwaters and sediment contribution projects. The influence of these elements on the stability of the beach profile and changes in sediment volume is analysed. The results reveal a dynamic morphological evolution highly influenced by protection and regeneration structures. Sediment accumulation is observed upstream of submerged breakwaters, indicating the effectiveness of these structures in reducing localized er osion. However, collateral effects are identified, such as the redistribution of sediments. The regeneration works, in combination with the submerged breakwaters, demonstrate a significant contribution to the restoration of the beach profile and protection against erosion. However, it highlights the importance of active management and continuous monitoring to address potential unintended impacts and adjust strategies as coastal morphology evolves. This study provides a detailed understanding of the interaction between submerged breakwaters, regeneration works and the morphological evolution of an urban beach. The findings inform the planning and design of future coastal management projects, highligh ting the need for integrated approaches that consider both protective structures and restoration measures to effectively address coastal erosion in urban settings, [CAT] L'erosió costanera planteja reptes significatius per a les platges urbanes i requereix solucions que combinin la construcció d'estructures de protecció amb mesures de regeneració del litoral. Aquest estudi investiga l’evolució morfològica d’una platja urbana encaixada en presència d’espigons submergits i obres de regeneració, analitzant el seu efecte en la mitigació de l’erosió costanera i la restauració del perfil de platja. Mitjançant l’anàlisi de campanyes topo-batimètriques utilitzant un projecte de GIS, s'avaluen els canvis temporals a la morfologia costanera en relació amb el diferent impacte de l’onatge en funció de la implementació d'espigons submergits i projectes d'aportacions de sediments. S'analitza la influència d'aquests elements a l'estabilitat del perfil de platja i als canvis de volum de sediment. Els resultats revelen una evolució morfològica dinàmica i altament influenciada per les estructures de protecció i regeneració. S'observa una acumulació de sediments a la part interna dels espigons submergits, cosa que indica l'eficàcia d'aquestes estructures per reduir la pèrdua de sediment cap a zones de més profunditat. Tot i això, s'identifiquen efectes col·laterals, com la redistribució de sediments. Les obres de regeneració, en combinació amb l’ espigó submergit, han estabilitzat força la platja i la protegeixen contra l'erosió. Tot i això, es ressalta la importància de la gestió activa i el monitoratge continu per abordar possibles impactes no desitjats i ajustar les estratègies a mesura que evoluciona la morfologia costanera. Aquest estudi ofereix una comprensió detallada de la interacció entre espigons submergits, obres de regeneració i l’evolució morfològica d’una platja urbana. Les troballes informen la planificació i el disseny de futurs projectes de gestió costanera, destacant la necessitat d'enfocaments integrats que considerin tant les estructures de protecció com les mesures de restauració per abordar eficaçment l'erosió costanera en

Narrow continental shelves such as those surrounding the Mediterranean basin are usually dominated by active depositional features such as major prodeltaic wedges located off major rivers (e.g. the Gulf of Lions, the northern Adriatic Sea), or by infralittoral wedges in settings where fluvial supply is more limited and hydrodynamic regimes are more energetic. However, the knowledge of the geomorphological patterns of undernourished shelves remains much less documented. In this contribution, we aim to characterize the submarine geomorphology and the sub-surface sedimentary bodies of a shelf sector located west of the Guadalfeo River, a major regional source in the northern margin of the Alboran Sea, where fluvial supply is provided by small seasonal rivers. To reach those goals, we analysed a data base comprising multibeam bathymetric and backscatter data, seafloor video images and Parasound acoustic sections. The studied shelf exhibits a distinctive zonation, where three major domains could be characterised. In the inner shelf, the most significant depositional bodies are composed by wedge-shaped deposits with limited lateral extent. Over the surface, several geomorphic indicators reveal the occurrence of high-energy processes in relation to the seasonal inputs of the Verde and Seco rivers. Recent to modern sedimentation seems to be much reduced distally. The middle shelf is marked by two main breaks of slopes, the surficial expression of highly reflective depositional bodies, likely marking the location of ancient paleo-shorelines and extensive development of paleo-coastal plains. The outer shelf is a flat domain covered by several elongated sedimentary bodies, which are disposed oblique to the middle shelf paleo-shorelines. Below those bodies, sub-surface architectures exhibit several unconformity-bounded regressive wedges. We discuss the shelf zonation observed in the study area considering the confinement of recent infralittoral and prodeltaic wedges to the inne

Bottom trawling is a fishing method that involves towing of nets along the seafloor to catch demersal species. The dragging of trawling gears along the seafloor results in scraping and ploughing of the surficial sediments, leading to the formation of turbid plumes of resuspended sediments and causing measurable changes in the seabed morphology. High-resolution multibeam data, side scan sonar, sediment grain size and vessel tracking data have been used to investigate the impact of bottom trawling on the seafloor morphology and surficial sediments of the northern Catalan continental shelf (NW Mediterranean), providing new insights into the impact of this anthropogenic activity on the seafloor. Multibeam data evidenced the occurrence of large-scale erosive features as a consequence of repeated scouring by fishing gears in localized areas. They are characterized by elongated (70-300 m wide and up to 8 km long) channelized areas of high backscatter with variable incision (from 0.2 m to 1.2 m). The spatial distribution of these morphologies shows a similar pattern to that observed in the fishing intensity, with maximum values in the areas of increased trawling intensity, corresponding to the main fishing grounds. Side scan sonar data also shows higher densities of trawl marks in these areas than in the surroundings. Sediment cores collected on these features show an upward-coarsening trend in the first 4-5 cm of the core, suggesting that part of the finer fraction resuspended by trawling is winnowed, increasing the sand content of the surface sediment. The identification of such large erosive morphologies in the main fishing grounds evidences that repeated trawling over the same fishing ground during decades can result in deep excavation of the seafloor, leading to permanent large-scale morphological changes. Furthermore, the evolution of these erosive features over a 13-year interval points towards long recovery periods after the cessation of trawling activities

The mesophotic domain is a poorly explored part of the oceans, notably in the Mediterranean Sea. Benthic communities in these depths are not well documented and as such are under higher risk from anthropogenic impacts. Hard substrate habitats in this depth window are not common and are a key ecotope. The Malta Plateau in the central Mediterranean, which is characterized by low sedimentation rates, offers a potentially unexplored domain for these features. Bathymetric and backscatter data offshore of the eastern coast of the island of Malta were used to identify > 1,700 small structures in mesophotic depths. These structures were verified to be biogenic mounds by dives. The mounds extend from several meters to tens of meters in diameter and occur in two main depth windows −40 to 83 meters below present sea level (mbpsl) and 83–120 mbpsl—each formed probably in a different stage during the last glacial cycle. The mounds are composed of interlocking bioconstruction by encrusting organisms and are colonized by sponges and various cold water corals (most of which are protected; e.g., Madrepora oculata). This unique and important habitat is currently under grave threat by human activity, most immediately by trawling and anchoring activity.

Modelling the response of sandy beaches to sea level rise is a major scientific challenge and several types of models can be applied. Given the long-time scales involved, different sources for model forcing must be combined (wave and sea-level, e.g., from buoys or hindcast models). We here apply the XBeach process-based morphodynamic model and the Q2Dmorfo reducedcomplexity model to El Castell, a Mediterranean embayed beach. The models are first calibrated with data measured during 161 days with an AWAC at 14 m depth in front of the beach. XBeach predicts reasonably well the bathymetric dynamics while Q2Dmorfo can only reproduce the shoreline evolution. The calibrated versions of the models are then applied using other potential forcing sources. The source for sea level does not affect the results but both models are sensitive to the wave forcing source., Peer Reviewed, Postprint (published version)

The SW Iberian margin host the present-day convergent plate boundary between Iberia and Nubia. Regional seismic activity is characterized by low to moderate events, although large historical and instrumental earthquakes (Mw>8.0) have been occurred, such as the 1755 Lisbon and 1969 Horseshoe ones. The NW-SE convergence (4-5 mm/yr) is accommodated by thrusts and a set of strike-slip faults that conforms a 600 km-long and 300 km-wide deformation band named the SWIM Fault Zone. The seismogenic Lineament South (LS), a WNW-ESE 350 km-long dextral strike-slip fault, is the most prominent among them and represents an important tsunami hazard for the SW Iberian coasts due to its extension, orientation and proximity to the coast. In this work we show multi-scale seismic profiles across the LS that reveal the Plio-Quaternary activity of the fault. The LS cuts and displaces the entire sedimentary sequence up to the seafloor, generating a set of continuous crest-and-troughs of hundreds of meters wide over the seafloor. Ultra-high resolution bathymetry acquired with AUV along two 15 km-long segments of the LS shows the presence of pull-apart basins, pressure ridges, semi-circular escarpments interpreted as collapsed structures, sedimentary features such as submarine dunes with lengths ranging from 200 m to 6 km, large longitudinal erosive bed-forms interpreted as furrows, and mass movement scars

It is usually assumed that the morphological evolution of embayed beaches on a microtidal coast largely responds to the degree of exposition to wave conditions; decreasing the mobility with the increase of beach indentation (and vice-versa). However, the amount of sediment arrivals on the beach, such as local streams inputs or longshore or cross-shore sediment transport, can modify that relationship. Here, we present the analysis of ten embayed beaches along the Catalan coast (NW Mediterranean) with very different morphometric and sedimentary characteristics, with the aim of identifying the most relevant parameters controlling the morphological evolution of embayed beaches at inter-annual and decadal scale. The study is mostly based on LIDAR topographic data collected from 2012 to 2017, and aerial photographs from 1946 to 2020. Based on these data, the main characteristics of the beaches were determined. The results show a net loss of volume on all studied beach at inter-annual scale and a general shoreline retreat during the last decades. Only one beach shows an opposite behavior due to the bypass of large amounts of sediment by longshore transport from the next beach. Small pocket beaches with medium-high indentation displayed higher variability on volume of the emerged beach and shoreline position, being more sensitive to changes induced by local factors, and standing up with the higher potential vulnerability. Among the possible causes of the erosion of these beaches, it is suggested that the reduction of the sedimentary contributions supplied to the beach by the streams could be a relevant factor

This work presents the geomorphologic characterization of the Blanes Canyon (northwestern Mediterranean), based on high- and very-high resolution multibeam bathymetry acquired in the framework of the ABRIC project. High-resolution hullmounted multibeam data (up to 5 m grid size) were collected along the entire submarine canyon head using a Kongsberg EM710 multibeam echo sounder (MBES). Additionally, the Hybrid Remotely Operated Vehicle (H-ROV) “Ariane” was used to acquire finescale morphology of vertical rocky walls within the canyon with unprecedented detail (80 cm grid size). The vertical mapping was performed using an EM2040 MBES mounted on the front of the H-ROV with a 45° orientation. High-resolution video footage was acquired on the same canyon walls with the ROV “Liropus”. Blanes Canyon has a marked structural character, deeply incising the margin and exposing Miocene to Pliocene successions. The tectonic control is evidenced by the rectilinear trajectories and sharp bends of the canyon axis, and by the presence of vertical rocky walls that can reach up 300 m in height. The canyon is asymmetric and has a smoothed eastern flank and a western flank dominated by a dendritic lattice of gullies. H-ROV bathymetric data on vertical cliffs allowed to trace the horizontal strata of Miocene ages, which offer the substrate for the development of benthic communities. Other identified fine-scale morphological elements include terraces, thalweg incision, under-cutting, scarps and rock avalanches. The study of the different-scale morphologies found in the canyon will allow a better understanding of its evolution trough time and the erosive processes involved

To investigate the topographic constraints caused by submarine canyon walls on near-bottom currents, four moorings arrays were deployed in the Blanes Canyon (NW Mediterranean) at ~600 m water depth during winter and spring 2020. Two moorings were placed at a main canyon head and two at the head of a canyon tributary, in regions characterized by narrow gorges and the presence of vertical canyon walls. This study was carried out during the Spanish ABRIC Project aimed to investigate sediment transport mechanisms and their influence on suspension feeder benthic communities. Preliminary results reveal that near-bottom currents were aligned with the canyon wall orientations and oscillated up- and down-canyon mainly at inertial frequencies. The highest current velocities measured at both study sites were ~35 cm/s and directed up-canyon, although the residual flows in both monitored sites were predominantly downcanyon. Suspended sediment concentrations did not exceed 4 mg/L and they mainly increased during down-canyon flows, which contributed to a continuous and persistent transfer of suspended particles towards deeper parts of the canyon. These new findings reveal a complex interaction between local hydrodynamics and steep canyon morphologies, which ultimately affect the ambient suspended sediment transport throughout the canyon, potentially driving the settlement and development of benthic communities inhabiting submarine canyon walls

Sorted bedforms have been widely described in sediment-starved continental shelves. They have been defined as sedimentary features consisting of isolated slight topographic depressions (commonly <1m) composed of coarse sediment within a larger region of finer sediment. However, recent observations revealed an unusual sorted bedform pattern that is dominated by coarse-grained sediment with patches of finer sediment. Repeated geophysical and geological surveys involving swath bathymetry and backscatter mapping, side scan sonar, grab sampling and sediment cores were used to characterise this particular pattern of sorted bedforms observed at three study sites in the Western Mediterranean: The Catalan, Marettino and Malta continental shelves. Swath data revealed complex sorted bedforms patterns at water depths of 10–60 m, characterised by a subtle relief (<0.4 m) and elongated and irregular shapes in plan view. Sediment characteristics varies significantly among the three study sites. Sorted bedforms on the Catalan continental shelf are composed of siliciclastic fine sands lying over a coarse sandy layer, whereas the sorted bedforms on the Malta and Marettino continental shelves are composed of bioclastic fine and medium sand overlying a coarser sediment layer (very coarse sand and gravel). Although the sorted bedforms show variable morphology and textural characteristics among the three study sites, they exhibit similar dynamics. Repeated surveys revealed that primary sorted bedform morphology was largely stable over a decadal timescale in the three study areas, with small changes in the coarse/fine sediment boundaries and significant changes on smaller-scale bedforms developed over the coarse domain in the Catalan continental shelf

Sentinelles de la Costa és un projecte de ciència ciutadana per a la monitorització de platges amb l'objectiu que els ciutadans participin activament en el procés científic i facin el seguiment de sectors específics de costa a què acudeixen de forma recurrent o esporàdica. A canvi, aquestes usuàries/is tindran a la seva disposició els resultats derivats de l'anàlisi de les imatges aportades (línies de costa i aplicacions de la seva monitorització), per tal de fer-los conscients dels canvis esdevinguts i quines en són les causes, apropant la ciència a la societat

Submarine canyons are deep, large-scale incisions that occur on the continental shelf and slope of all ocean margins. These landforms serve as preferential particle-transport conduits that connect the coastal zone with the deep-sea. Canyons have been studied for decades and are among the most iconic submarine geomorphic features. Advances in marine technology are increasingly providing new understanding of the physical and biological processes that take place in canyons, which are also notoriously affected by the impact of anthropogenic activities. In this article we describe the main geomorphic characteristics of submarine canyons and synthesize the past and current knowledge on their formation, evolution, global distribution and hydrodynamical and ecological significance.

"Centinelas de la Costa" aims, through a coordinated team of different entities and experts in coastal research, to promote the scientific culture of citizens, in terms of the changes that our coast shows as a consequence of different natural processes or of anthropic origin. It is articulated in two main actions with different spatial scope: (i) Action at the regional level: with the aim of implementing and promoting the means and resources already available within the international initiative of CoastSnap towards different sectors of society. Adding to existing resources, new functionalities have been implemented and a contest has been launched to encourage the use of the CoastSnap App and generate community. (ii) Action at the local level: a common space and format of a mobile application has been created, "Centinelas de la costa", that allows the different members of the project team to provide solutions according to the specific needs of each location. This action is complemented with training days for volunteers in data collection, in collaboration with local agents

Se realizaron 14 campañas topo-batimétricas desde la playa emergida hasta los 15 m de profundidad, a lo largo de 1 km en la playa de Castelldefels (Delta del Llobregat, Barcelona) durante el periodo 2011-2020. Se analizan las variaciones morfológicas que tienen lugar, los cambios volumétricos y sus posibles implicaciones en los intercambios sedimentarios en el perfil litoral. Los principales cambios morfológicos están causados por los desplazamientos transversales de las barras de arena, generalmente hacia tierra durante condiciones de buen tiempo y hacia mayor profundidad durante las tormentas más fuertes. Los cambios volumétricos sugieren que el retroceso de la línea de costa durante la última década aporta sedimento a la parte superior de la playa sumergida, mientras que los eventos más extremos producen una transferencia de sedimento hacia la plataforma continental, que podrían ser parcialmente irrecuperables para la dinámica litoral. El balance sedimentario resultante es negativo, Postprint (updated version)

The effects of massive dumping of dredged material were studied during and after the last large Barcelona port expansion. A benthic tripod equipped with a current meter, a turbidimeter and a video camera was deployed at the edge of the Barcelona shelf dumpsite. Additionally, sediment cores were taken before, during and after dumping at the tripod location. Previously, sediment samples were taken in the port expansion area. Dumping generated frequent (10–19 per day), high (>203.2 mg L−1) and short (50–90 min) suspended sediment concentration peaks along with shock waves that increased currents velocities. The dumped sediment formed a thin laminated deposit that accumulated beyond the limits of the dumpsite. This material was finer and had a lower trace metal content than the previous sediment at the dumpsite and the surface samples taken from the dredged area. Unconsolidated sediment left after dumping was available to be resuspended and advected, generating higher ambient suspended sediment concentrations (0.8–15.0 mg L−1) than before the dumping (0.4–2.0 mg L−1), which lasted several days. Results of this work suggest that after the end of a massive dumping in low dispersive environments, such as on the dumpsite of the Barcelona continental shelf, turbidity should continue to be monitored until the recovery of natural values. The characteristics of the bottom sediment should be periodically controlled beyond the limits of the dumpsite if the dumped material spilled outside its boundaries. Environmental guidelines for dredging activities should include specific actions for long-lasting massive dumping episodes regarding their spatial extent, considering the effects of the shock waves generated by dumping, and also the temporal evolution of the effects of dumping after its completion

Continental margins are transitional areas between the land and the deep ocean where large amounts of particulate matter are supplied, transported, and ultimately deposited in the deep sea. High-energy hydrodynamic processes such as storms, ocean currents, or internal waves and tides, as well as bottom trawling activities contribute to the resuspension and remobilization of these particles. These mechanisms favor their transference from the continental shelf to the continental slope and maintain high concentrations of particulate matter in the water column forming nepheloid layers. The temporal evolution of the hydrographic and nepheloid structure in the upper slope off Vancouver Island (British Columbia, Canada, NE Pacific) was assessed by analyzing 4 months (from mid-August to late-November 2018) of sensor data from Ocean Networks Canada (ONC) NEPTUNE cabled seafloor observatory. The distribution of particulate matter during the study period illustrated a well-defined turbidity structure consisting of surface nepheloid layers (SNLs) at <100 m depth associated to primary and secondary productivity, intermediate nepheloid layers (INLs) between 150 and 300 m depth at the shelf-break and upper slope domain, and bottom nepheloid layers (BNLs) developed at >400 m depth. Moderate storm events occurred during fall when the more intense INLs were recorded at shelf-break depths. However, not all the INLs recorded during this period occurred in coincidence with these storms, indicating that these INL detachments were modulated by a different sediment resuspension mechanism. Analyses of fishing vessel activity during the study period revealed that trawlers operated over the same depth range as these INLs. Our results suggest that, in combination with the regional currents, the presence of continuous fishing along the continental slope off Vancouver Island contributes to the advection of suspended sediment particles, playing a major role in their transfer as nepheloid layers