Brittany Coast Research Articles

Instant Controlled Pressure Drop (DIC) as an innovative pre-treatment for extraction of natural compounds from the brown seaweed Sargassum muticum (Yendo) Fensholt 1955 (Ochrophytina, Fucales)

The effects of the Instant Controlled Pressure Drop (DIC) technology on the recovery of natural compounds from the brown seaweed Sargassum muticum (Yendo) Fensholt 1955 (Ochrophytina, Fucales) were investigated. Fresh biomass of S. muticum was collected on the Brittany Coast, France. Both fresh and Air Impingement-Dried (AID) thalli of 3 and 10 cm length were submitted to DIC during 20 s or 90 s of processing time under 100 or 800 kPa of saturated steam pressure. DIC treatment significantly improved the extraction of sulphate groups at 90 s, and carotene at 20 s under 100 kPa in thalli of 10 cm. While, coupling AID to DIC, the content of neutral sugars, proteins and antioxidants were higher in AID + DIC treatments. Further, a significant increase of 20 % in fucose-containing sulfated polysaccharides and 30 % in sodium alginate under 100 kPa during 90 s, compared to oven-dried, was observed. The biomass of the invasive S. muticum treated by DIC and AID + DIC represented a valuable contribution for extraction of natural compounds. Advantages for industrial integration of DIC were discussed.

First Use of Free-Diving Photo-Identification of Porbeagle Shark (Lamna nasus) off the Brittany Coast, France

A large number of pelagic shark species have declined significantly in recent decades due to overfishing, bycatch, and habitat degradation. Whereas porbeagle sharks have become scarce due to a reduction in their populations around the world, recent stock evaluations are giving positive signals about the evolution of the North-Eastern Atlantic stock size. The porbeagle shark (Lamna nasus), an offshore pelagic species with a wide distribution, is designated by IUCN as Globally Vulnerable and Critically Endangered for Europe and subject to various international conservation conventions. An increasing number of observations are reported off the Brittany coast of Trégor. The ecological role of this area for the species is still unknown and greater knowledge is needed to develop and apply sustainable management measures on a local and international scale. This study represents the first use of photo-identification on porbeagle sharks in order to improve the ecological knowledge of the species in the Trégor area. These results confirm the effectiveness of this method, with 19 of the 131 individuals identified being re-sighted, indicating an interesting degree of site fidelity and showing a sex ratio of 100% females. Observations of individuals over several years allowed the researchers to discuss the relevance of the different types of marks. The findings suggest that the Trégor area off the Brittany coast serves as a seasonal residence for female porbeagle sharks, especially between May and October. This study represents a successful first step in the use of photo-identification for this species. It offers technical support for the sharing of the methodology and provides some biological knowledge allowing researchers to discuss potential sustainable management measures for the conservation of porbeagle sharks in the study area and their habitats while needed.

The Enzyme-Assisted Extraction of compounds of interest in agriculture: Case study of the red seaweed Solieria chordalis (C. Agardh) J. Agardh

For centuries, seaweeds have been spread on fields to improve soil properties and crop yield. Over the last thirty years, the use of seaweed-based extracts has attracted increased attention in agriculture. In comparison with raw seaweed, extracts may be more concentrated in bioactive molecules such as macro/microelements, peptides, polysaccharides and metabolites. These molecules are usually obtained by conventional Water Extraction (WE), which is most often time consuming, with low selectivity and extraction yields. Over the last decade, tailored extraction processes using microwave, ultrasound and enzyme have demonstrated their advantages to obtain enriched seaweed extracts. In this context, the aim is to determine, for the first time in Solieria chordalis, whether Enzyme-Assisted Extraction (EAE) is an effective way of producing extracts enriched in macro/microelements and Plant Growth Regulators (PGRs), which are some of the main compounds of interest for plant nutrition and biostimulation. The red seaweed S. chordalis (C. Agardh) J. Agardh (Gigartinales, Rhodophyta) has been chosen as a case study model since it proliferates on the South Brittany coast (France) during the winter. The extraction yield and biochemical composition of the extracts are determined to assess the efficiency of EAE in comparison with WE. The results demonstrate that EAE increases the contents compared with WE in terms of neutral sugars (×2) and proteins (×1.3). In addition, PGRs in S. chordalis are quantified here for the first time. The most abundant PGRs present in S. chordalis and its extracts are Indole 3-Acetic Acid (IAA), 1-Amino-1-Cyclopropane-Carboxylic Acid (ACC) and Salicylic Acid (SA). Indeed, EAE allow us to enrich the content of the extracts in SA (×3), ACC (×3) and IAA (×6), compared with WE. Therefore, this study demonstrates that EAE is an efficient process for enriching S. chordalis extracts in various compounds, and should be investigated on other seaweeds for agricultural purposes.

Multi-year renewal of green tides: 18 years of algal mat monitoring (2003–2020) on French coastline (Brittany region)

To better understand the green tide phenomenon impacting French coastline and give guidance to stakeholders to elaborate effective mitigation plan, an extensive survey has been deployed on Brittany hot spots. Based on 18 years monitoring database, the objectives of this work were to investigate the inter-and-intra annual evolutions of Ulva beaching, and to assess the parameters driving green tide annual renewal. The yearly cumulated area of Ulva mat on the Brittany coast averaged 2,42 ± 0,84 ha, of which 55 ± 12 % % was reported within Saint Brieuc-Binic Bay, with a maximal beaching generally observed in July. The renewal of green tide at spring time seems to be correlated with the Ulva bloom from the previous autumn period, particularly in bays with low exposure to swell. The residual stock, defined as Ulva fragments maintained in healthy conditions during the winter season, appears as highly dependent on nitrogen summer flows.

When phytoplankton do not bloom: the case of the dinoflagellate Lepidodinium chlorophorum in southern Brittany (France) assessed by environmental DNA

Green seawater discolorations caused by the marine dinoflagellate Lepidodinium chlorophorum are frequently observed during summer along southern Brittany coasts (NE Atlantic, France). Here, the ecology of L. chlorophorum is studied during a non-bloom period using high-throughput sequencing metabarcoding of environmental DNA (eDNA) samples for the detection of this species at low concentrations. Sediment samples (for metabarcoding and cyst analyses) were collected in January–February 2019 and water samples from two stations were collected at three water depths in September–March 2019–2020 and 2020–2021 (for metabarcoding and environmental parameters). The protistan community was dominated by dinoflagellates and was homogenous in the water column. Amplicon sequence variants (ASVs) associated with the genus Lepidodinium were detected in autumn–winter at low relative abundances (minimum: 0.01%). Increases in Lepidodinium abundance were positively correlated with pulses of ammonium re-suspended from bottom sediments. Although Lepidodinium eDNA (<1%) was detected in the sediments, no cyst morphotypes could be associated with Lepidodinium, and germination experiments revealed no Lepidodinium-like cells, leaving in doubt the existence of resting cysts of this species in the seed bank. It is hypothesised that temporary Lepidodinium cells remained present in the water column at low concentrations during the autumn–winter period, awaiting ammonium input from sediments to initiate growth, and that blooms develop when water column stratification and river input provide favourable environmental conditions for biomass increases.

High-Resolution Drone Images Show That the Distribution of Mussels Depends on Microhabitat Features of Intertidal Rocky Shores

In this study, we used orthomosaics and a digital surface model (DSM) generated from drone surveys to (1) characterize the distribution of mussel (Mytilus galloprovincialis) aggregations at high resolution (centimeters), and (2) evaluate the role of topographic features, intertidal height, slope, and orientation angle in determining mussel distribution on two rocky shores oriented differently on both sides of a beach on the French Brittany coast. We first developed and tested a mussel visualization index (MVI) for mapping mussel aggregations from drone images. Then, we analyzed mussel distribution on the two shores. The results showed a contrasted total mussel-occupied area between the two rocky shores, with a higher occupation rate and a clear pattern of distribution depending on topographic features on the rocky shore oriented to the west. Intertidal height, and its associated immersion time, was the main factor determining mussel distribution. An optimum intertidal height was found in the center of the distribution height range, at c.a. 4.5 m above the lowest astronomical tide (LAT), where individuals are under immersion phase on average 43% of the time. Within this optimum, the occupation rate of the mussels was significantly higher in microhabitats facing south and west, particularly at intermediate slope angles. These results demonstrate the role of microhabitat topographic features on the development of intertidal mussels and their final distribution. Furthermore, the results highlight the importance of mesoscale structures of habitats (e.g., 100 m), which seem to be responsible for the differences we observed between the two shores. Our methodological approach highlights the main advantage of using high-resolution drone images to address ecological processes in intertidal ecosystems. Indeed, drone imagery offers the possibility to assess small-scale interactions between individuals and habitat conditions over a wide area, which is technically infeasible from fieldwork approaches or by using satellite remote sensing due to their lower resolution. Scale integration and methodological complementarity are powerful approaches to correctly represent the processes governing the ecology of intertidal ecosystems. We suggest using this methodology to monitor long-term changes of sentinel sessile species.

The Rance tidal power station: Toward a better understanding of sediment dynamics in response to power generation

A three-dimensional coupled hydrodynamic and morphodynamic numerical model was developed to analyze sediment dynamics in the Rance estuary, in response to the tidal power station (TPS) built near the mouth in the 1960s. The Rance estuary is a relatively small low-discharge steep-sided ria, located along the Brittany coast in northern France, with a maximum spring tidal range of 13.5m. Taking advantage of this significant tidal regime, the first and currently the second largest operational tidal power station in the world was built at the estuary’s mouth, with peak output capacity of 240MW. After calibration and validation of the model for present-day conditions, suspended sediment concentration (SSC) and bed level evolution were evaluated at tidal and fortnightly scales for different scenarios, with and without TPS. Peak SSC are reached during spring tides and specifically during the estuary’s infilling (flood) stage where both turbines and sluice gates are open. Unbalanced with sediment transport during ebb, sediments are accumulated in the main channel of the upper estuary. Under natural tidal forcing (i.e., without TPS), simulations show that an estuarine turbidity maximum forms in the upper estuary, and sediment deposition is significant. However, sedimentation rates are two times lower than those observed in the presence of the TPS. A possible alternative for reducing sediment accumulation in the upper estuary would be the opening of sluice gates simultaneously with the turbines during falling tide, to enhance ebb currents that would allow particles transport towards the estuary’s downstream.

Spatio-temporal dynamics and biogeochemical properties of green seawater discolorations caused by the marine dinoflagellate Lepidodinium chlorophorum along southern Brittany coast

Blooms of the marine dinoflagellate Lepidodinium chlorophorum cause green seawater discolorations affecting the recreational use and the tourism economy along southern Brittany (NE-Atlantic, France). Hypoxic conditions associated with phytoplankton biomass recycling are suspected to cause fauna mortalities. An in situ monitoring was performed in 2019 to characterise the seasonal variability of L. chlorophorum. This species was observed from May to November, with a maximum abundance in June–July. Specific bloom sampling demonstrated a dominance of L. chlorophorum within microphytoplankton, and documented its vertical distribution. Satellite observation was used to compute the surface extent of the bloom and to highlight the importance of small-scale temporal variability, with tidal currents being a primary driver of surface distribution of the bloom. Stratification contributed to promoting the bloom of L. chlorophorum. High concentrations of phosphate and ammonium, together with transparent exopolymer particles (TEP), were recorded within the bloom. Bacterial stimulation, leading to nutrient remineralisation or mucus facilitating mixotrophy, is suggested to sustain bloom development. Hence, TEP production might provide an ecological advantage for the dinoflagellate, conversely causing negative effects on the environment and biological resources through hypoxia. These first insights constitute a baseline for further studies in other ecosystems impacted by this species.

Three-dimensional hydrodynamic model of the Rance estuary (France) influenced by the world’s second largest tidal power plant

The Rance estuary is a small steep-sided ria, located in the Brittany coast of northern France, with a maximum spring tidal range of 13.5m and an average river discharge of 7m3/s. Taking advantage of this significant tidal range, the Rance tidal power station (RTPS) was built in the 1960s as the world’s first and largest tidal power plant, with peak output capacity of 240 Megawatts. It is currently the second world’s largest tidal power installation after the Sihwa-Lake tidal barrage. The RTPS has two active parts: a barrage of 6 sluice gates and a structure of 24 turbines. Despite a well-known effect of the plant on damping estuarine water levels, little attention has been given to currents vertical distribution and the plant's impact on the dynamics of freshwater-saltwater interface. Therefore, a three-dimensional model of the Rance estuary was developed. Moreover, currents and salinity measurements were carried out to validate the numerical model. Simulated and measured currents showed that (i)the RTPS induces an acceleration of flood currents directly upstream of the sluice gates and (ii)ebb currents are strengthened by the narrowness of the Saint-Hubert-Port. Finally, salinity analyses assessed the dynamics of the freshwater-saltwater interface which is pushed further upstream during summer.

Genetic diversification and life-cycle of the polychaete Capitella spp. from the English Channel: evidence for sympatric cryptic species and alternative reproductive strategies

Polychaetes belonging to the genus Capitella are known to represent a complex of opportunistic cryptic species that dominates the macrobenthos of organically enriched sediments, such as muddy areas particularly rich in sulfide. With the exception of the species, Capitella capitata (Fabricius) from West Greenland, Capitella spp. from the European Atlantic coast have never been accurately characterized both genetically and morphologically and were often reported as capitata in the literature. The life cycle of these European worms has not been described properly either, despite their widespread use as bio-indicators in ecological studies. The present study provides the first morphological description of Capitella specimens collected along the Brittany coast and the English Channel up to the entrance of the North Sea and their genetic diversification in this region. Both morphological and molecular data are congruent and support the co-occurrence of cryptic species at the tip of Brittany. The most frequent French mt lineages, C-Channel1, C-Atlantic and C-Channel2, although well distinct from Capitella teleta, are also divergent but closer to C. capitata initially described from Greenland. Following barcoding, the most abundant species (C-Channel1) was isolated and reared in the laboratory to describe its life cycle and predict both its dispersal ability and ecological success in the face of the sulfidic muddy habitats of the French harbors.

French Mediterranean and Atlantic populations of the brown algal genus Taonia (Dictyotales) display differences in phylogeny, surface metabolomes and epibacterial communities

Considered as holobiont systems, marine macroalgae and their microbiota constitute functional units displaying a large diversity of interactions. Main factors driving the assembly of epiphytic microbiota, and subsequent interactions with the host, are often associated to environmental differences but also to host taxonomy displaying specific chemical properties. Here, through a large sampling effort focused on the brown algal genus Taonia (Dictyotales) on both the French Mediterranean and Atlantic coasts, we aimed to highlight the relative importance of the effects of environment, host taxonomy and surface metabolome on the epibacterial community of these seaweeds. Phylogenetic analyses revealed two distinct clusters, one grouping only the specimens from the French Mediterranean coasts and the second one composed of samples from Brittany. Both metabarcoding and surface metabolomics revealed clear differences between Mediterranean thalli and those collected in Brittany. Strong environmental differences associated with algae from these two different geographical areas could both be involved in this clustering. For example, oxidative stress due to higher irradiance intensities might induce a higher expression of fucoxanthin in Mediterranean samples, while higher eutrophication levels could explain the higher abundance of Alteromonas spp. on algal samples from Brittany coast. In a lesser extent, genetic differences observed between thalli from these two locations could also influence surface metabolomes and thus host-microbiota interactions.

Les foyers éclatés : Les émigrés français à l’île de Jersey et le facteur genre de l’exil

This essay focuses on the temporary settlement of refugees on the Channel Island of Jersey during the French Revolution, analyzing this borderland community with a gendered lens. Until recently, French historians have depicted the emigration as a direct response to French and British anti-émigré legislation and rhetoric, each wave contingent upon the political climate in France. This perspective, however, misses much of the complexity of Jersey’s unique place in the emigration as a French speaking island along the Brittany coast with a British military presence. A social analysis of this emigration from western and northern France to the Channel Island of Jersey reveals the complex motives of household migration and the realities of temporary exile in a fractured world. Domestic ruptures among these French emigrants were met with a mixed response from the host country (Britain) and the local authorities who managed these refugees. Viewing their losses evoked a crisis of masculinity and demanded a humanitarian response that highlighted female fragility.

Are benthic nutrient fluxes from intertidal mudflats driven by surfacesediment characteristics

A broad sampling program was carried out in the spring of 2019 on the Brittany coast to assess how the surface sediment characteristics drive the benthic effluxes of ammonium (NH + 4) and phosphate (PO 4) from intertidal mudflats. A total of 200 sediment samples were characterized by their porosity, grain-size, elemental composition and pigment contents, as well as the benthic fluxes of NH + 4 and PO 4 determined by core incubations. The results showed that (1) a high phaeopigment and iron-bound phosphorus content (Fe-P) and a low porosity were significantly related to the high PO 4 flux, and (2) a high porosity and the TN:Org-P ratio in the sediment organic matter (SOM) were related to the high NH + 4 flux. This indicated that PO 4 fluxes would be more driven by the redox status of the sediment through the desorption of Fe-P under specific anoxic conditions during the algal decomposition. NH + 4 fluxes would be more driven by high NH + 4 recycling rates from SOM mineralization and high sediment-water exchanges, enhancing the diffusion of NH + 4 to the overlying water. The present study allowed to highlight the large variability in the benthic nutrient fluxes at the regional scale, as a result of the connections between microbial (SOM mineralization), chemical (adsorption-desorption) and physical (diffusion) processes.

Effect of COVID-19 spring lockdown on low-frequency ambient noise levels along the Brittany coast

Shipping noise is a major source of ocean noise in Brest bay, and includes cargo vessels, navy ships, fishing boats and recreational vessels with frequencies overlapping the range of marine animal sound emission. Changes in vessel activity provide unique opportunities to quantify the relationship between traffic levels and soundscape conditions in biologically important habitats. Using an autonomous recorder deployed from March 20 to July 29 2019 inside Sainte-Anne harbor in Brest area we assessed the effect of the 2020 spring COVID-19 lockdown (March 17 to May 11) on ambient noise levels. We measured the mean power spectral density levels in different third-octave bands (including Marine Strategy Framework Directive bands centered on 63 Hz and 125 Hz). The March 20–May 15 (during lockdown) levels were up to 2.6 dB re 1 μPa2/Hz below the May 15–July 28th (after lockdown) levels, corresponding to nearly a halving of acoustic power.

Impact of ear protection on occurrence of exostosis in surfers: an observational prospective study of 242 ears.

The aim of the study was to investigate the efficacy of ear protection (earplug and surf hood) in preventing the development of external auditory exostosis (EAE) in surfers. We performed a prospective observational study. Volunteer surfers were recruited from June 2016 to October 2017 on the Brittany coast in France. Each participant filled in a questionnaire and underwent otoscopic digitalized photography to establish the degree of external ear obstruction by two different practitioners. The correlation between the percentage of external ear obstruction and the time spent in water with or without protection was evaluated. Risk factors of EAE were assessed. Two hundred and forty-two ears were analysed. The incidence of EAE was 89.96% with an average rate of obstruction of 37.65%. Risk factors for EAE were male sex (p = 0.0005), number of years practicing surf (p < 0.0001) and symptoms of ear obstruction (p = 0.0358). A significant correlation was found between EAE severity and number of hours spent in water without any protection (earplugs or surf hood) (p < 0.0001). No correlation was found between EAE severity and time spent in water with earplugs (p = 0.6711) but a correlation was identified between obstruction and time spent in water with surf hood (p = 0.0358). Wearing earplugs is an effective way to prevent EAE in surfers unlike surf hood.

Hydrodynamics of a hyper-tidal estuary influenced by the world's second largest tidal power station (Rance estuary, France)

The Rance estuary is a relatively small low-discharge steep-sided ria, located along the Brittany coast in northern France, with a maximum spring tidal range of 13.5 m. Taking advantage of this hyper-tidal regime, the first and currently the second largest operational tidal power station in the world was built at the estuary's mouth and has been in operation since the 1960s. Despite the well-known effect of damping of estuarine water levels, little attention has been given to quantifying the influence of the plant on the propagation and asymmetry of the tidal wave inside the estuary. In this study, hydrodynamics and tidal wave patterns were analyzed in this anthropogenically influenced estuarine system. A two-dimensional depth-averaged numerical model of the Rance estuary was developed. Two scenarios without the tidal power plant involving the dam's pre- and post-construction bathymetry (1957 and 2018 respectively) and present-day conditions scenarios were designed, to highlight the impact of bed evolution and the tidal power station on hydrodynamics and tidal asymmetry. Numerical results showed that, without the structure, bathymetric evolution did not substantially influence estuarine hydrodynamics. Nevertheless, on the estuary-side of the dam, the presence of the tidal power plant induced (i) a decrease in both tidal range and tidal prism, (ii) an increase of low water levels, and (iii) a decrease in both flood and ebb currents. Contrastingly, the region close to the structure reacted differently to plant operating modes, with an increase in flood currents (ebb currents) upstream of the sluice gates (downstream of the turbines). For both the natural condition and the artificially-induced hydrodynamic forcing due to the presence of the plant, numerical results showed that the Rance estuary mainly exhibits flood-dominant behavior, with a longer duration of falling than rising water and stronger peak flood currents than ebb currents. Spanning a period of approximately 60 years, this study presents a quantitative analysis of the influence of the tidal power station on the hydrodynamics in the Rance estuary, and its possible consequences for sediment dynamics. This approach is novel for this particular enclosed water body, characterized by the presence of a dam at its mouth and a lock at its uppermost limit.

Tidal Patterns and Sediment Dynamics in a Hypertidal Estuary Influenced by a Tidal Power Station

Rtimi, R.; Sottolichio, A. and Tassi, P., 2020. Tidal patterns and sediment dynamics in a hypertidal estuary influenced by a tidal power station. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1520–1524. Coconut Creek (Florida), ISSN 0749-0208.The Rance estuary is a relatively small low-inflow steep-sided ria, located in the Brittany coast of northern France, with a maximum spring tidal range of 13.5 m at the mouth. Taking advantage of this hypertidal regime, the first and largest operational tidal power station in the world was built at the estuary mouth and is in operation since the 1960s. Despite a well-known effect of the plant on the damping of estuarine water levels, little attention has been given to the propagation of the tidal wave along the estuary. Moreover, net siltation has been reported by several observations, but there is no specific knowledge on the role of the plant on sedimentation. In this study, tidal wave patterns and sediment dynamics are analyzed in this particular man-engineered system. A numerical model, based on a two-dimensional depth-averaged approach is implemented to predict the tide propagation and tidal currents along the estuary. Numerical results are analyzed and discussed to highlight the role of the plant on the transformation of the tidal wave in the estuary and its possible consequences on sediment dynamics and morphological evolution.

Long, Medium, and Short-term Shoreline Dynamics of the Brittany Coast (Western France)

Stéphan, P.; Blaise, E.; Suanez, S.; Fichaut, B.; Autret, R.; Floc'h, F.; Cuq, V.; Le Dantec, N.; Ammann, J.; David, L.; Jaud, M., and Delacourt, C., 2019. Long, medium, and short-term shoreline dynamics of the Brittany Coast (western France). In: Castelle, B. and Chaumillon, E. (eds.), Coastal Evolution under Climate Change along the Tropical Overseas and Temperate Metropolitan France. Journal of Coastal Research, Special Issue No. 88, pp. 89–109. Coconut Creek (Florida), ISSN 0749-0208.This paper aims to analyze the shoreline changes of coastal accumulations (sandy and gravel beaches/barriers) of Brittany (Western France). Three long, medium, and short term spatio-temporal scale observations are taken into consideration for the assessment of shoreline dynamics at this regional scale. Firstly, the long-term shoreline position evolution is based on a comparison of two sets of aerial orthophotos (1949-1952 and 2006-2009). A total of 652 beaches were analyzed in order to map and quantify erosion (35% of the total studied coastline), stability (38%), and accretion (27%) over the last 60 years. In detail, these percentages vary significantly according to the beach/barrier morphologies (spits vs pocket beaches), sediment composition (sandy vs gravelly), and hydrodynamic context (exposed vs sheltered). Secondly, a pluri-annual (i.e., medium-term) shoreline change analysis based on five representative beaches was conducted. This analysis was also based on image processing using sets of aerial photos taken every five years over the last 60 years (1948-2013). Results show an alternation of significant erosion- and accretion-dominated periods (respectively EDP and ADP), with six main EDP (i.e., periods 1962-1968, 1977-1978, 1980-1985, 1987-1990, 1993-1997, and 2013-2014) related to an increase in the frequency of extreme water levels associated with storm events. Finally, the short-term change analysis based on high-frequency monitoring of 11 sites was carried out over the period 1998-2017. These surveys, based on field topo-morphological measurements, highlight the impact of five morphogenetic events associated with significant storm events: 1998-2000 (storms Lothar and Martin in December 1999), 2008 (storm Johanna on March 10, 2008), the winter of 2013-2014 (a cluster of storms in January, February, and March 2014), 2016 (storm Ruzica/Imogen on February 8, 2016) and 2018 (storm Eleanor on January 2, 2018). A relevant recovery phase, which took place between 2008 and 2012 due to the calm and cold winters, was also recognized. The identification of parameters involved in shoreline variations at these three timescales is important for future management options of the Brittany coast.

The PERCEBES project: science for the spatial management of the stalked barnacle fishery in the Atlantic Arc

The PERCEBES project: science for the spatial management of the stalked barnacle fishery in the Atlantic Arc

Using sentinel-1A SAR wind retrievals for enhancing scatterometer and radiometer regional wind analyses

ABSTRACTScatterometer surface wind speed and direction observations in combination with radiometer wind speeds allow to generate surface wind analyses with high space and time resolutions over global as well as at regional scales. Regarding scatterometer sampling schemes and physics, the resulting surface wind analyses suffer from lack of accuracy in areas near coasts. The use of the synthetic aperture radar (SAR) onboard the Sentinel-1A satellite attempts to address the enhancement of surface wind analyses issues. In this study, SAR wind speeds and directions retrieved from backscatter coefficients acquired in interferometric wide (IW) swath mode are used. Their accuracy is determined through comprehensive comparisons with moored buoy wind measurements. SAR and buoy winds agree well at offshore and nearshore locations. The statistics characterizing the comparison of SAR and buoy wind speeds and directions are of the same order as those obtained from scatterometer (Advanced SCATterometer (ASCAT) and RapidScat) and buoy wind comparisons. The main discrepancy between SAR and buoy data are found for high wind speeds. SAR wind speeds exceeding 10 m s–1 tend to be underestimated. A similar conclusion is drawn from SAR and scatterometer wind speed comparisons. It is based on the underestimation of SAR backscatter coefficient (σ°) with respect to σ° estimated from scatterometer winds and the geophysical model function (GMF) named CMOD-IFR2 (Ifremer C band MODel). New SAR wind speeds are retrieved using CMOD-IFR2. The corrected SAR retrievals allow better determination of the spatial characteristics of surface wind speeds and of the related wind components in near-coast areas. They are used for enhancing the determination of the spatial structure function required for the estimation of wind fields gridded in space and time at the regional scale. The resulting wind fields are only determined from scatterometer wind observations in combination with radiometer retrievals. Their qualities are determined through comparisons with SAR wind speeds and directions, and through their application for determination of wind power off Brittany coasts.