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The eastern part of the Bay of Seine (English Channel) is highly impacted by harbour activities and the dumping of dredged sediment by the port authorities of Le Havre (GPMH) and Rouen (GPMR). Sediment dredged by the GPMH (2–2.5 millions of m3 per year) has been disposed at the subtidal Octeville site since 1947. Since the 2000s, mainly fine sediment (80% of fine particles <63 μm) has been disposed using alternate mosaic boxes with limited thickness (0.2 to 0.6 m per box per year), preventing the accumulation of disposed sediment in some parts of the dumping site. During the period August 2016 to September 2017, an experimental study was set up to identify the spatio-temporal changes of the macrobenthos collected at ten stations on six dates: three stations where different volumes of sediments were dumped (from 41,000 to 186,000 m3), two stations located within the Octeville site but without dumping operations during the study and five stations outside the disposal site (northern and southern zones). The Taxonomic Richness, total abundance and abundances of the polychaete Owenia fusiformis show negative correlations with the volumes of deposited sediment, whereas use of the AMBI (AZTI's Marine Biotic Index) and B2OA (Benthic Opportunist Annelids Amphipods) indices does not allow us to distinguish the impacted zone. Our study shows that the impact of dumping remains local and the benthic habitats display a high degree of resilience with rapid recovery of the community after the cessation of disturbance. Recommendations on the future long-term strategy are proposed to improve assessment and minimise the impact of dumping sediment on this benthic habitat.

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We explore the coastal morphology along an uplifting 500 km-long coastal segment of the Central Andes, between the cities of Chala (Peru) and Arica (Chile). We use accurate DEM and field surveys to extract sequences of uplifted shorelines along the study area. In addition, we consider continental pediment surfaces that limit both the geographical and vertical extent of the marine landforms. We establish a chronology based on published dates for marine landforms and pediment surfaces. We expand this corpus with new 10Be data on uplifted shore platforms. The last 12 Ma are marked by three periods of coastal stability or subsidence dated ~12-11 Ma, ~8-7 Ma and ~5-2.5 Ma ago. The uplift that accumulated between these stability periods has been ~1000 m since 11 Ma; its rate can reach 0.25 mm/a (m/ka). For the last period of uplift only, during the last 800 ka, the forearc uplift has been accurately recorded by the carving of numerous coastal sequences. Within these sequences, we correlated the marine terraces with the sea level highstands (interglacial stages and sub-stages) up to MIS 19 (790 ka), i.e., with a resolution of ~100 ka. The uplift rate for this last period of uplift increases westward from 0.18 mm/a at the Peru-Chile border to ~0.25 mm/a in the center of the study area. It further increases northwestward, up to 0.45 mm/a, due to the influence of the Nazca Ridge. In this study, we document an unusual forearc cyclic uplift with ~4 Ma-long cycles. This periodicity corresponds to the predictions made by Menant et al. (2020) based on numerical models, and could be related to episodic tectonic underplating (subducting slab stripping) beneath the coastal forearc area.

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The southern coast of Argentina is composed of many coarse-grained coastal barriers, which are mostly concentrated at the mouth of a few large rivers that drains the Andean mountains. As the Patagonian estuaries are characterized by tidal ranges that are among the largest in the world, coastal barriers are exposed to high amplitude tide-induced sea-level changes as well as strong tidal currents. In order to better understand the influence of tides in wave-built sedimentary bodies, an in-depth analysis of the architecture of barrier systems has been realized at the mouth of the Santa Cruz estuary (50°S). Maximum tidal range is 12 m in this estuary. A great variety of morphologies compose both sides of the estuary inlet, from simple spits and barrier spits to beach ridges. Barrier spit and beach ridges characterize the southern side, whereas elongated simple spits and spit barriers isolating large tidal flats are more developed on the northern side. As a consequence of this configuration the northern system is much wider than the southern one (6 km vs 1 km). The site was investigated using ground-penetrating radar (400 MHz GSSI antenna), along with the analysis of digital elevation models and some sedimentological observations. Cross-shore and long-shore profiles, with a penetration depth up to 4 meters, show a large range of radar facies attributed to erosional surfaces, beach face progradation, along-drift elongation, hooks and spit terminus development, and washover deposits. The analysis of the radar architecture allows reconstructing the development of individual morphology, and helps to differentiate the influence of wave- and tide-related processes. The most open-sea barrier spit systems show a classic development controlled by the wave-related littoral drift entering into the estuary (onshore directed), and enhanced due to shore parallel flood currents into the inlet. In contrast, in the innermost part of the northern side, spits and barrier spits feature contrasting morphologies, structures and directions of elongation, either landward or seaward, reflecting a complex combination between wave-, tide-and fluvial dynamics on their construction. One of the spits imaged with the GPR shows an intense reflection that has been associated with the top of the tidal flat on which the spit migrates (Fig. 1). The GPR lines highlight the control of underlying substrate on spit morphologies A same morphology is thus characterized by different architectures; in Figure 1B the prograding sequence follows a transgressive sequence, while in Figure 1C the transgressive sequence cannot be observed in the architecture due to the highest elevation of the tidal flat. In the southern side of the estuary, the barriers show extensive progradational sequences with different slopes that seem to depend on the spit morphology, and therefore on the exposure to ocean swells.

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The current development of human activities at sea (e.g. land reclamation, maritime activity and marine renewable energy) is leading to a significant increase in the number of infrastructures installed in marine settings. These artificial structures provide new hard-bottom habitats for many marine organisms and can thus modify the structure and functioning of coastal ecosystems. In order to better evaluate the nature of these modifications as well as the potential benefits and/or impacts generated, it becomes essential to develop assessment methods that can be applied to a wide variety of study sites from harbours to coastal offshore environments. In this context, our study aims to review the different methods and indicators available which are used to measure the modifications of biodiversity and ecological functioning generated by such structures. Among the methods reviewed, we highlight some that were developed specifically for artificial structures, and others intended for various primary uses but which have been successfully transposed to artificial structures. Nevertheless, we also point out the lack of reliable methods concerning some biological ecosystem components impacted by artificial structures. In this context, we require the adaptation or creation of brand-new indicators to achieve a better characterisation of the ecological impacts generated by these structures. Overall, this study highlights a very high number of existing methods, which provide stakeholders with useful tools to study the impacts of artificial structures, and identifies the need to develop integrative indicators to enhance the deployment of new artificial structures.

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Abstract. The North Atlantic coast of Morocco has been affected historically by marine submersion events resulting from both storms and tsunamis and causing human and economic losses. The development of proactive adaptation strategies requires the study of these events over centennial to millennial timescales. Using a 2.7 m sediment core sampled from the Tahaddart estuary, we have been able to reconstruct past marine submersion events on this coastal area of Morocco over the last 4000 years. The high-resolution sedimentological and geochemical analysis conducted on this core allows us to identify 14 sediment layers attributed to marine high-energy events. The core was dated with isotopic techniques (137Cs, 210Pbex, 14C) and the outcomes reveal that three sediment layers are in connection with two major historical marine submersion events. The first layer mentioned as E1 seems to fit with the great Lisbon tsunami in 1755 CE (Common Era), an event dated for the first time on the Atlantic coast of Morocco. The other two layers referred as E13 and E14 were dated between 3464 and 2837 cal BP and correlated with marine submersion deposits found on Spanish and Moroccan coasts, which confirms the existence of a major high-energy event (around 3200 BP) similar to the one in 1755 CE.

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Due to the climate change, it is necessary to modify the energy modes of production. The mix energetic, based on renewable energies as tidal currents, is one of the solutions to decrease the energy production carbon footprint. This article focuses on hydrodynamic interactions in Alderney Race (France), which is the most energetic tidal site in Western Europe with a maximum potential of 5.1GW according to Coles et al. (2017). The impact of a winter storm occurring during spring tide is assessed thanks to numerical modeling with a 3D fully-coupled wave–current model and in-situ data. This study starts to analyze the impacts of the storm on the wave field and the current effects on waves. Then, the modifications of the current and tidal stream energy caused by waves are discussed. After a successful validation step with excellent PBIAS and R2 scores, the main finding are: (i) although the current intensity is strong (around 3–4m s−1), the wave action significantly changes the vertical profile of the current, with a reduction of the PBIAS by a factor of 1.78 between simulations with and without wave effects, (ii) ocean waves affect the tidal asymmetry, with a flood current whose intensity is 13% higher than for the ebb current, inducing a decrease of 30% in the tidal stream energy, (iii) the flow is very sensitive to the angle between the directions of propagation of waves and current, with an acceleration or a reduction of the velocity, as observed in the presence of a 3D turbulent structure, (iv) current effects on waves cause a wavenumber shift, changes in significant wave height (modulated by tide), wave direction due to refraction and an increase of the energy transfer from waves to ocean ascribed to the wave breaking. By a feedback mechanism, the modifications of the wave field by current and water level significantly alter the flow with a decrease of its velocity when waves propagate against current. This study shows that the 3D wave–current interactions need to be considered during a storm even during a spring tide event where currents are the strongest.

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Abstract Integrative and spatialized tools for studying the effects of a wide variety of ecosystem drivers are needed to implement ecosystem-based management and marine spatial planning. We developed a tool for analyzing the direct and indirect effects of anthropic activities on the structure and functioning of coastal and marine ecosystems. Using innovative modelling techniques, we ran a spatially explicit model to carry out an ecological network analysis (ENA) of the effects of climate change (CC), of an offshore wind farm (OWF) and of multiple fishing scenarios on the Bay of Seine (eastern part of the English Channel) ecosystem. ENA indices described the effects of those different drivers in a holistic and spatial way. The spatial analysis of ecosystem properties revealed local and global patterns of modifications attributed to CC, while the OWF resulted in localized changes in the ecosystem. This ability of ENA indicators to detect human-induced changes in ecosystem functioning at various spatial scales allows for a more integrative view of the effects of human activities on ecosystems. ENA indices could be used to link both local and global ecosystem changes, for a more cross-scale approach to ecosystem management.

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Abstract Integrative and spatialized tools for studying the effects of a wide variety of ecosystem drivers are needed to implement ecosystem-based management and marine spatial planning. We developed a tool for analyzing the direct and indirect effects of anthropic activities on the structure and functioning of coastal and marine ecosystems. Using innovative modelling techniques, we ran a spatially explicit model to carry out an ecological network analysis (ENA) of the effects of climate change (CC), of an offshore wind farm (OWF) and of multiple fishing scenarios on the Bay of Seine (eastern part of the English Channel) ecosystem. ENA indices described the effects of those different drivers in a holistic and spatial way. The spatial analysis of ecosystem properties revealed local and global patterns of modifications attributed to CC, while the OWF resulted in localized changes in the ecosystem. This ability of ENA indicators to detect human-induced changes in ecosystem functioning at various spatial scales allows for a more integrative view of the effects of human activities on ecosystems. ENA indices could be used to link both local and global ecosystem changes, for a more cross-scale approach to ecosystem management.

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This study describes for the first time in the central Mediterranean Sea the effects of bottom trawling on macrobenthic fauna in tidal channels of the Kneiss Islands in the Gulf of Gabès, Tunisia. Following a BACI protocol, two control stations (protected by artificial reefs) and two trawled stations (impacted stations) were sampled during a period with the absence of bottom trawling activity (the COVID-19 pandemic lockdown period from March to May 2020) and during a trawled period. Although bottom trawling had no impact on sediment composition, this anthropogenic activity reduced the concentration of dissolved oxygen and had a noticeable effect on water column turbidity. The absence of trawling led to a significant increase in biomass, number of species, and abundance of total macrofauna. This illustrated the negative effect of trawling activity in shallow waters and the high resilience of macrobenthic communities of the tidal ecosystem of the Kneiss Islands. In the future, it would be very important to control the use of this destructive fishing gear due to its negative impact on the marine habitat and macrofauna, which represents essential prey for fishes and birds living in this protected area.

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