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This study records the number of Peracarida (Cumacea, Isopoda, Mysida, Lophogastrida and Tanaidacea) from Algerian coastal waters. A total of 170 species are reported with the highest richness observed in the Isopoda (71 species), then the Cumacea with 43 species, the Mysida and Tanaidacea with 27 species each and the Lophogastrida with only two species. The diversity of Peracarida in Algeria is high, corresponding to 60% of the species recorded for the Mediterranean Sea. A geographical analysis of the distribution of the species shows that the Algerian fauna has a close similarity with taxa reported from both the European and African coasts of the Atlantic Ocean. This reflects the influence of Atlantic waters along the North African coasts extending from Morocco to Tunisia in the south of the Mediterranean Sea, which is related to the connection via the Strait of Gibraltar. For the Algerian coasts only five Peracarida species may be considered as Non-Indigenous Species.

International audience; The French coast of the Atlantic and English Channel (EC) is promising for the development of Marine Renewable Energy (MRE), including wind, wave, and tidal stream, due to the high velocity of currents in some parts of the area. This paper, focusing on wind and tidal energy, discusses how the implementation of MRE converters influences biodiversity, and vice versa, through biofouling and reef effects. The understanding of these interactions requires the knowledge of the hydro-sedimentary conditions and the macrofauna. The research on these topics, performed at the Continental and Coastal Morphodynamic laboratory (M2C) (UNICAEN, France), is presented through a multi-disciplinary approach by i) studying the hydrodynamic conditions and the macrofauna in Alderney Race, ii) studying the biofouling effects on tidal turbines and their influence on the turbulent wake, iii) assessing the hydro-sedimentary impacts induced by the offshore wind farm, like scouring, and iv) taking an ecosystem approach on MRE, such as the reef effect. From an ecological perspective, the reef effect can be responsible for changes in the structure and function of the ecosystem. Although several studies have analyzed this effect at the species-or community-scale, the propagation of the reef effect at the ecosystem-scale remains unclear. Thus, understanding these ecosystem-scale effects is urgent for future research. From an engineering perspective, biofouling changes the structural characteristics (i.e., supplementary mass) of the converters and thus, affects their performance.

International audience; A yearlong seasonal survey was carried out during 2016–2017 at 26 stations representing four tidal channels of the north-western part of the Gulf of Gabès (Tunisia). The area studied (characterized by a maximum tidal range of 2.3 m) was subjected to diverse anthropogenic pressures: from the phosphate industry and its metallic pollution, unauthorized bottom trawling in shallow water (known locally as ‘Kiss’), and organic pollution from the nearby urbanized areas. A total of 23,506 invertebrates representing 311 taxa were collected. Dominant taxa were the polychaetes with 51.4% of the individuals collected and 39.3% of the taxa, the amphipods (18.6% and 15.5%), the tanaids (12.3% and 2.6%), and the molluscs (11.5% and 18.3%). The mean annual abundances varied widely from one channel to another: from 300 to 3700 ind·m−2. The stations located in deeper waters exhibited greater variability. Measurements of abundance revealed seasonal changes with maximum values in winter, spring, and lower numbers in summer. Each tidal channel was characterized by specific features in the fauna. The macrofauna were dominated by the polychaete Cirratulus cirratus (mainly in spring) and the amphipod Microdeutopus anomalus (mainly in winter), whilst both of the tanaids, Apseudopsis gabesi (the first sighting reported for the area) and A. mediterraneus, were found to be abundant in winter in at least one of the four channels. Species are mainly deposit feeders, herbivorous and omnivorous. The analyses on spatial and temporal changes of the macrofauna population revealed variations according to the composition of the fauna increasing or falling along the channels and as a function of seasonal changes. In spite of a high level of anthropogenic activities, the Ecological Status (ES) assessment (applying the AMBI and M-AMBI indices) attributed High or Good ES for 10 stations, Moderate ES for 11 stations and five stations showed a poor ES at least during one season. Sampling subtidal stations in the future to survey long-term degradation of such ecosystems of the coastal environment of the Gulf of Gabès in Tunisia is proposed.

(IF 4.95; Q1); International audience; The “Rade de Cherbourg” (RdC, Cotentin) hosts the only marine salmon fish farm along the French coasts. High hydrodynamic regime would limit, there, organic matter (OM) accumulation directly under the cages, and enhance the transport of OM in the surrounding of the cages. This study was aiming at (1) monitoring the impact of a salmon fish farm on ecological quality statuses (EcoQs) of the RdC based on a benthic foraminiferal biotic index, (2) comparing EcoQs assessment results between foraminifera and macrofauna, and (3) in fine assessing the potential for benthic foraminifera to become an alternate biological quality element. In 2014 and 2015, bottom sediments of the RdC were sampled at 13 stations under and outside the farm for sedimentary (grain size and OM), and living foraminiferal and macrofaunal analyses. For benthic foraminifera, Exp(H’bc) was used to determine EcoQs, while H’, AMBI and BO2A indices were used for benthic macrofauna. Rank-frequency distributions (RFDs) were calculated for both groups. Ecological quality statuses based on foraminifera and macrofauna indicated a moderate degradation of the environmental conditions, shifting from excellent outside the farm to poor under the cages for foraminifera and from excellent to moderate for macrofauna. This study showed that benthic foraminifera are as reliable as macrofauna to assess EcoQs in the RdC. It offers interesting perspectives to monitor the health of marine systems based on benthic foraminifera. Furthermore, results obtained with RFDs suggested that this approach should be considered in the assessment of the good environmental status within the European marine strategic framework directive. Finally, diversity proved to be efficient in monitoring the health of the RdC, suggesting that it should not be set aside for the benefit of sensitivity-based indices.

(IF 2.93; Q1); International audience; As part of the energy transition, the French government is planning Offshore Wind Farm (OWF) constructions in the next decades. An integrated ecosystem approach of two future OWF sites of the Eastern English Channel (Courseulles-sur-mer and Dieppe-Le Tréport) was developed to model the marine ecosystems before the OWF implementation. Such ecosystem models allow simulating the possible reef and reserve effects associated to the presence of the farm, and to character the overall changes in the food-web functioning. This holistic view of OWF effects could be replicated on other sites and form the basis of an ecosystem based management of marine renewable energies. However, to use these models for management purpose, they need to be validated. In order to do so, stable isotope ratios of nitrogen were used for determining the accuracy of the effective trophic levels computed in these two models. Results showed that trophic levels estimated by the two models were consistent with the trophic levels estimated by the independent isotopic data. In the context of OWF development and cumulative impacts analysis, this step of validation of the models is essential for developing their use by management actors and policy makers. © 2020 Elsevier Ltd

(IF 0.78 [2018]; Q3); International audience; Two galatheoid anomurans, Gastrosacus raboeufi n. sp. and G. sp., the earliest members of the genus Gastrosacus von Meyer, 1851 known to date, are recorded from upper Bathonian strata in Calvados (Normandy, France). In this respect, we consider the enigmatic Palaeomunidopsis moutieri Van Straelen, 1925 from the middle Bathonian of Giberville (Normandy) to be a nomen dubium. As far as carapace morphology of G. raboeufi n. sp. is concerned, we note that it reveals a number of primitive characters that are indicative of a close relationship with the Gastrodoridae amongst paguroid anomurans.

(IF 1.74 [2018]; Q2); International audience; The mysid Neomysis americana (S.I. Smith, 1873), which originates from North-American estuaries, was reported for the first time in 2017 in the Seine estuary (English Channel, France). This sighting represents the second reported occurrence of this species in Europe, following the record of two individuals in 2010 in the Wadden Sea (Netherlands). Its appearance seems recent since no individuals were recorded in previous intensive sampling carried out in the navigational channel and North Channel of the Seine estuary since the middle of the 1990s. In 2017, a total of 2674 individuals of N. americana were sampled, showing the rapid establishment of a reproductive population which was favorised by the decline of the autochthonous population of Neomysis integer (Leach, 1814).

International audience; Since the beginning of the 2000’, the French government ambition was to have an offshore wind production formed 40% of the renewable electricity in 2030. Three calls tenders of Offshore Wind Farms (OWFs) construction have been pronounced since 2011. However, no offshore wind farm (OWF) had been constructed at the end of 2017 due to long administrative procedures and numerous appeals in justice, at French and European levels. Nevertheless, several studies have been enterprised to identify the environmental conditions and ecosystem functioning in selected sites before OWF implantations. However, these studies are generally focused on the conservation of some species or groups of species, and there is no holistic study on the effects of the construction and operation of OWF on an ecosystem taken as a whole. In 2017, a complete and integrated view of the ecosystem of two future OWF sites of the eastern English Channel (Courseulles-sur-Mer and Dieppe-Le Tréport) was developed to model the marine ecosystems before OWF implementation and to simulate reef effects due to new spatial occupation of maritime territory. Results contribute to a better knowledge of the impacts of the OWFs on the functioning of marine ecosystems. They also allow to define recommendations for environmental managers and industry in terms of monitoring the effects of marine renewable energy (MRE), not only locally but also on other sites, at national and European levels.

(IF 1.20 [2018]; Q2); International audience; Here we report the first record of the red mouthed rock shell Stramonita haemastoma (Linnaeus, 1767) (Gastropoda, Muricidae) a predatory gastropod newly introduced to the English Channel. This species originally lives in the western Atlantic, eastern Pacific and Mediterranean Sea. Three specimens were collected on Pecten maximus at St-Martin-de-Bréhal, Normandy, France, on 2 February 2018. We present some hypotheses about the mode of introduction of S. haemastoma and its potential impact on the ecosystem in the English Channel.

(IF 4.49; Q1); International audience; A one-year experimental study was conducted in 2012–2013 to assess the physical and biological impacts of dumping dredge spoil composed of muddy fine sand (1 million m3) in a benthic zone with medium-grained sands in the eastern part of the Bay of Seine. Previous study showed that the impact is local and the benthic habitats show a high degree of resilience after a short dumping phase and the recovery of the community is observed just after cessation of the disturbance. Moreover, during the deposition phase, Impacted and Influenced zones can be distinguished from a Non-impacted zone. A combination of indices (BO2A, AMBI benthic indices) and modelling tools were applied to study the dumping dredge spoil impact. Results highlighted that these different indices allowed detecting the dumping operations effects. In addition, results from the AMBI et BO2A indices revealed that the system showed a high resilience after a short dumping phase. Lastly, the macrofauna and demersal fishes appear to be stimulated in the Influenced zone during the dumping phase, thus supporting the Intermediate Disturbance Hypothesis.

The European seas are known to be the recipient of several hundreds of Non-Native Species (NNS) due two main origins: shipping and aquaculture. More than 160 NNS had been recorded along the Normandy coast, which remains low in comparison with the number of marine invertebrate species known in the English Channel (> 3,000). The main sites of introduction are the harbours, especially Le Havre and the oyster cultivation zones. Among these NNS, 56 are present in Normandy and considered invasive along the European coasts, but only ten (one macro-algae and nine invertebrates) are invasive in Normandy. Six examples are illustrate, the molluscs Magallana gigas, Crepidula fornicata, Ensis leei, and Ruditapes philippinarum, the polychaete Ficopomatus enigmaticus and the crab Hemigrapsus sanguineus. The two first species have changed the dynamics and functioning of the coastal ecosystems, while the others have lower impact. In fact, the oyster and the manila clam are now key species for the French economy, while the rapid expansion of the other species change biodiversity in the more colonised sites. The ALEX (ALien Biotic IndEX) proposed by Cinar and Bakir in 2014 for the Mediterranean Sea is used for the first time in Atlantic waters.

The polychaete Chaetopterus variopedatus lives in large, leathery U-shaped tubes in subtidal sands or gravel. The species is scarcely distributed in the English Channel and thus not easy to find. The studied animals and their associated fauna originate from beam trawls or were washed up on beaches in Normandy. In the upper part of the tube, near the prostomium of C. variopedatus, we found the following commensal species: the crab Asthenognathus atlanticus and the polychaetes Harmothoe glabra and Gattyana cirrhosa. For the tropical-temperate crab A. atlanticus our findings represent an extension of its geographical range. Moreover, at the tube’s extremity several epifaunal species were present, among them the ascidian Styela clava, an introduced species from Japan. Undoubtedly, tubes of C. variopedatus provide an excellent habitat for associated species and further studies involving the interaction of the host and its commensals could prove very interesting. Our results suggest also that these tubes represent a stepping-stone habitat for the introduction of non-native species and the geographical extension of tropical-temperate species in the English Channel.

The Gulf of Gabès on the southern coasts of Tunisia in the central part of the Mediterranean is a very shallow basin, characterized by semidiurnal tides, attaining a range of 2.3 m during spring tides. The intertidal zone was covered by extended Zostera (Zosterella) noltei Hornemann, 1832 beds mainly developed around the Kneiss Islands while tidal channels ensured the water circulation in this sub-tropical environment with very low freshwater input and high summer temperature. In spite of protected conventions, the area remained under high human pressures: overfishing, and the impact of the pollution of the phosphate industry. Intensive sampling in both intertidal and shallow subtidal zones during annual cycles permitted to identify a rich macrofauna which increase considerably the species known in this eastern part of the Mediterranean Sea. More than 50 species are added for the Tunisian fauna. Moreover, patterns of diversity are analysed with the sediment types, presence or absence of Zostera noltei seagrass bed, and human pressures. The list of the collected species are compared with those of surrounding areas in both Western and Eastern Mediterranean Sea.

International audience; The eastern part of the English Channel (north-eastern Atlantic) in a megatidal environment is one of the most impacted area in the world wide ocean. To the traditional fish activities and maritime transports with dredging and deposit spoil sediment which impact the ecosystem, aggregate extractions and implementation of offshore wind farms increase the pressures in this shallow epicontinental sea. The soft-bottom sea bed was mainly covered by sandy gravels and gravelly sand located offshore under high tidal currents while medium sand and muddy fine sand were deposit along the coast in area with weak currents. A large number of benthic indices had been recently developed mainly to the implementation of the European Water Framework Directive, but to structural assessment, development of more integrate method such as Ecological Network Analysis with the Ecopath model permit to furnish a functional assessment of the benthic habitats. Several studies in diverse sediment type under human pressures or future activities with reef and protected scenarios within an offshore windfarm permit to evaluate the suitability of structural and functional indices to reveal spatio-temporal statutes and changes of the Ecological Status of the benthic ecosystems.

(IF 2.87; Q1); International audience; As part of the energy transition, the French government is planning the construction of Offshore Wind Farms (OWFs) in Normandy. These OWFs will be integrated into an ecosystem already facing multiple anthropogenic disturbances. A holistic view of cumulated impacts (OWF construction, global warming and fisheries) were developed on the Courseulles-sur-Mer’ ecosystem through the use of a qualitative mathematical modelling approach. This modelling approach provides the mean to consider alternative hypotheses about how the ecosystem structure and function affects its dynamics. Alternative models were constructed to address the different hypotheses regarding the behaviour of top predator (whether the top predators will be scared away by the OWF or attracted by the reef effect), impacts of global warming and changes in fisheries activities. Key findings from these analyses are that the OWF construction could lead to an increase in benthos species and fish benthos feeders whatever the perturbation scenario, while the predicted response of top predators was ambiguous across all perturbation scenario. Qualitative modelling results can play a vital role in decision making by improving long term planning for the marine environment but also as a tool for communication with the public and so contribute to a better acceptability of the Marine Renewable Energy (MRE) project.

The French government is planning the construction of offshore wind farms (OWF) in the next decade (around 2900 MW). Following the European Environmental Impact Assessment Directive 85/337/EEC, several studies have been undertaken to identify the environmental conditions and ecosystem functioning at selected sites prior to OWF construction. However, these studies are generally focused on the conservation of some species and there is no holistic approach for analysing the effects arising from OWF construction and operation. The objective of this article is to promote a sampling strategy to collect data on the different ecosystem compartments of the future Dieppe-Le Tréport (DLT) wind farm site, adopting an ecosystem approach, which could be applied to other OWFs for the implementation of a trophic network analysis. For that purpose, an Ecopath model is used here to derive indices from Ecological Network Analysis (ENA) to investigate the ecosystem structure and functioning. The results show that the ecosystem is most likely detritus-based, associated with a biomass dominated by bivalves, which could act as a dead end for a classic trophic food web since their consumption by top predators is low in comparison to their biomass. The systemic approach developed for DLT OWF site should be applied for other French and European installations of Offshore Wind Farm.

International audience; The Manila clam Ruditapes philippinarum (Adam and Reeve 1850) was introduced into France in the 1970s and now dominates the European clam Ruditapes decusattus (Linnaeus 1758) in the intertidal zone of the western Cotentin (English Channel). While it has successfully colonized a large variety of sediment habitats, from muddy sand to gravel, the densities remain< 20 ind. m-2. In this extensive intertidal zone, it is difficult to estimate the density as well as the stock of such dispersed species of clam. Our study has three main objectives: i) to determine a better sampling strategy to estimate the density of Ruditapes spp. clam populations; ii) to assess the spatial distribution of clams at the scale of the western coast of Cotentin (30 km of coastline from North to South), and iii) to evaluate the stock and annual quantities of clams fished by recreational and professional fishing in this area. For the estimation of densities and stock of Ruditapes spp., it is better to continue using a quadrat area of 1 m² for a large number of random sampling points (≥ 400) to estimate with the greatest possible spatial precision the local and regional abundance of such low-density populations. Sampling techniques with smaller quadrats and more sampling points lead to higher standard deviation of the mean densities. The species are distributed in four main patches covering between 0.54 to 3.14 km² out of a total of 10.47 km² (~ 10% of the intertidal zone). The 2015 stock (Ruditapes> 40 mm, legal catch size) in these four patches is estimated as 382 t (fresh weight with shell) for a total of harvest of 122 t (32% of the adult stock), which corresponds to a catch of 8 t by professional fishers and 113 t by recreational fishers.

(IF 1.74; Q2); International audience; Asthenognathus atlanticus Monod, 1932, is reported here for the first time in the area around Dieppe-Le Tréport (Normandy coast in the eastern part of the English Channel). A total of 26 specimens were collected in 2015–2016 from fine and coarse sands at water depths between 12 and 25 m. Two specimens were found in the stomach of two thornback rays Raja clavata. The eastward progression of A. atlanticus is consistent with tidal residual currents in the English Channel. The period of global warming is likely favorable for this easterly progression, and the species could reach the southern part of the North Sea in a few years. Our observations in the eastern part of the English Channel also illustrate a new commensal association between the tubicolous polychaete C. variopedatus and the crab A. atlanticus, the latter being found in a variety of soft-bottom sediments ranging from muddy to coarse sands, in agreement with reports of its presence in the Rade de Cherbourg and the Bay of Seine.

Background Finding of a single female specimen of the African mangrove crab Perisesarma alberti Rathbun, Bull Am Mus Nat Hist 43: 379–474, 1921, in the intertidal zone of the eastern part of the Bay of Seine, English Channel, France. Result Identification and description of the recorded crab, photographs and measurements of the single specimen. Comparison with reports from West African mangroves. Conclusion It is unlikely to assume an African origin of the collected species. It is more likely a species escaped from an aqua-terrarium, even if the common species in the French aquarium trade have an Australasian origin.

The Erymidae Van Straelen, 1925 had a worldwide distribution during the Jurassic and the Cretaceous. Twenty-seven species among four genera were reported in the Late Cretaceous, but confusions in diagnoses have led to wrong generic identifications of many erymid species. In the light of recent clarifications of the diagnoses of erymid genera, the Late Cretaceous species are here reviewed. We recognize thirteen of them including three European species which benefit of new descriptions: Palaeastacus sussexiensis (Mantell, 1824), Enoploclytia leachi (Mantell, 1822) and Enoploclytia seitzi Glaessner, 1932. Furthermore, a comparison of the Late Cretaceous erymid fauna with that from the Early Cretaceous emphasizes some changes. A decrease in diversity on genus and species level is noted with the absence of Eryma Meyer, 1840 in the Late Cretaceous and the predominance of Enoploclytia M’Coy, 1849 (including almost half of the species). Despite the scarcity of the fossil record, our palaeobiogeographic interpretations led us to propose hypotheses about the provenance of North American populations in the end of Early Cretaceous and in Late Cretaceous: (1) their supposed absence since the Callovian (Jurassic) is due to collecting and/or reporting bias or (2) they were the result of migrations of European populations. Moreover, the report of a chela assigned to Stenodactylina cf. armata (Secretan, 1964) in France confirms the existence of migration routes between European and Malagasy faunas during the Late Cretaceous.

Among the polychaetes, the Syllidae comprise numerous species whose study over many years has benefitted from valuable revisions and descriptions of new species in Europe. This abundant literature proves very useful for revisiting the taxonomy and distribution of the Syllidae in the English Channel (EC), mainly as regards existing studies on coarse sediment communities in the eastern part of the Channel. This habitat is one of the most widespread in the EC and is known as favourable for the small polychaete fauna including Syllidae. A 2-year survey (winter and summer sampling periods) covering 19 stations, associated with theBranchiostoma lanceolatumcoarse sand community offshore Dieppe-Le Tréport, led to the identification of 6537 individuals from 29 taxa including 27 species. Six fine sand stations were also sampled in which only 12 individuals were collected. Among these species, seven are new for the EC polychaete fauna and six others are observed for the first time in the eastern part of the EC. All the new species for the EC are warm temperate species previously only known south of the Bay of Biscay. The Syllidae list given in Dauvinet al. (2003) has been re-analysed and amended with our list and that of the Chausey Archipelago study (Olivieret al., 2012). To date, 91 Syllidae species have been recorded in the EC and are established mostly in coarse sediments.

International audience; As part of the energy transition, the French government is planning the construction of three offshore wind farms in Normandy (Bay of Seine and eastern part of the English Channel, northwestern France) in the next years. These offshore wind farms will be integrated into an ecosystem already facing multiple anthropogenic disturbances such as maritime transport, fisheries, oyster and mussel farming, and sediment dredging. Currently no integrated, ecosystem-based study on the effects of the construction and exploitation of offshore wind farms exists, where biological approaches generally focused on the conservation of some valuable species or groups of species. Complementary trophic web modelling tools were applied to the Bay of Seine ecosystem (to the 50 km 2 area covered by the wind farm) to analyse the potential impacts of benthos and fish aggregation caused by the introduction of additional hard substrates from the piles and the turbine scour protections. An Ecopath ecosystem model composed of 37 compartments, from phytoplankton to seabirds, was built to describe the situation " before " the construction of the wind farm. Then, an Ecosim projection over 30 years was performed after increasing the biomass of targeted benthic and fish compartments. Ecological Network Analysis (ENA) indices were calculated for the two periods, " before " and " after " , to compare network functioning and the overall structural properties of the food web. Our main results showed (1) that the total ecosystem activity, the overall system omnivory (proportion of generalist feeders), and the recycling increased after the construction of the wind farm; (2) that higher trophic levels such as piscivorous fish species, marine mammals, and seabirds responded positively to the aggregation of biomass on piles and turbine scour protections; and (3) a change in key-stone groups after the construction towards more structuring and dominant compartments. Nonetheless, these changes could be considered as limited impacts of the wind farm installation on this coastal trophic web structure and functioning.

A Before/During/After Control-Impact approach is used to assess the effects of Port 2000 on the suprabenthos in the North Channel (NC) of the Seine estuary during the period from September 2001 to October 2015. Since the beginning of Port 2000 construction (2002-2005), the NC is affected by an increase of salinity (marine influence) and input of sand. The suprabenthos changes are mainly characterised by an increase in species richness in the upper part of the NC and a decrease in species density and biomass of the dominant mysid species over time. Multiple stressors (natural and anthropogenic) have been operating simultaneously (hydrological changes, construction of Port 2000, supplementary dredging) rendering the interpretation of the biological changes difficult. Thus, the present results evidenced a combination of changes in the Seine Estuary not only attributed to the impact of the Port 2000 construction.

International audience; This study aims to identify the composition and the distribution of macrobenthic communities in the Rade de Cherbourg (RdC), on the north coast of the Cotentin Peninsula (Normandy, France). The results show the presence of six main benthic communities: (1) Crepidula fornicata banks in coarse mixed sediment, (2) Amphipholis squamata and Apseudopsis latreillii in mixed sediment, (3) Melinna palmata in muddy sand, (4) Melinna palmata in mixed muddy fine sand, (5) Spio decoratus in fine sand and (6) Spio decoratus and Apseudopsis latreillii in very fine and fine sand (from EUNIS classification). The RdC appears as a rich soft bottom macrobenthic habitat in a semi-enclosed bay, surrounded by hard-bottom environments. However, current and future projects related to human activities (harbour extension, salmon farming) could impact the benthic communities. Moreover, the structure and composition of the muddy fine sand and fine sand communities, which are dominant within the area of the RdC, show similarities with comparable communities found in the western English Channel under the influence of Atlantic waters.

National audience; La rade de Cherbourg est une zone particulière puisqu’elle présente une diversité de faciès sédimentaires (vase, sable fins, cailloutis, graviers et affleurements rocheux), avec la présence de zones envasées, phénomène anachronique dans cet environnement soumis à un fort hydrodynamisme (courant de marée atteignant jusqu’à 1ms-1 au nord de la grande rade). La présence d’une ferme d’élevage de salmonidés ainsi que des ports de pêche et de plaisance, des lignes de ferries et les projets liés à l’accueil des Energies Marines Renouvelables en font une zone aux défis économiques et environnementaux importants pour la Normandie. Dans ce cadre, la rade de Cherbourg fait l’objet d’un programme de monitoring intégrant les différents compartiments environnementaux. Les résultats présentés concernent un état zéro de la qualité de l’environnement dans l’ensemble de la rade avant l’extension de terre-pleins (37 ha). La distribution des faciès sédimentaires présents dans la zone en liens avec les communautés benthiques sont présentés. Cette étude met en évidence la présence de cinq faciès sédimentaires fins et de six communautés benthiques. La rade de Cherbourg apparait comme une enclave de substrats meubles, dans un environnement voisin de nature plus grossière, permettant l’installation d’une faune riche et diversifiée en comparaison à celles situées à l’extérieur de la rade. L’impact de la ferme d’élevage est minimisé par la présence du fort hydrodynamisme permettant la remise en suspension des particules sédimentaires, des fèces ainsi que de la nourriture non-consommée. La présence, en fortes abondances, de certaines espèces benthiques caractéristiques d’un enrichissement en matière organique est cependant mise en évidence sous les cages. D’autre part, en comparaison avec d’autres communautés présentes en Manche (côtes anglaises et françaises), les communautésbenthiques des sables fins et des sables envasés de la Rade, sont plus proches de celles présentes en Manche Ouest en termes d’assemblages faunistiques et d’abondances.

La rade de Cherbourg, au nord du Cotentin (Normandie), est une zone de substrats meubles caractérisée par un fort hydrodynamisme. La présence d’une ferme d’élevage de salmonidés et les projets liés à l’accueil des Energies Marines renouvelables (EMRs) en font une zone aux défis économiques et environnementaux importants. En effet, des travaux d’extension du port de Cherbourg en grande rade (débutés en janvier 2015), menés afin d’accueillir la filière hydrolienne mais également des activités complémentaires liées à l’éolien en mer, vont engendrer, entre autre, un accroissement du trafic maritime et une augmentation du dragage, impactant probablement la qualité de l’environnement et les communautés benthiques à proximité. Ainsi, cette étude a pour but d’étudier la distribution des communautés benthiques avant l’extension des terre-pleins et de déterminer la qualité de l’environnement dans l’ensemble de la rade et à proximité de la ferme aquacole. Les résultats obtenus montrent la présence de six communautés benthiques, en plus de la communauté à Zostera (Zostera) marina. La rade de Cherbourg apparait comme une zone riche et diversifiée. L’impact de la ferme d’élevage est minimisé par la présence du fort hydrodynamisme qui permet la remise en suspension des particules. Cependant, on note la présence en fortes abondances de certaines espèces caractéristiques d’un enrichissement en matière organique (le tanaïdacé Apseudopsis latreilli, le polychète Melinna palmata et le bivalve Thyasira flexuosa). D’autre part, en comparaison avec d’autres communautés présentes en Manche (côtes anglaises et françaises), les communautés des sables fins propres et celles des sables envasés de la Rade de Cherbourg, sont plus proches de celles présentes en Manche Ouest qu’en Manche Est ou le long des côtes anglaises.

International audience; The present study analyses the spatio-temporal variability of the macrozoobenthos from the intertidal zone of the Kneiss Islands (Gulf of Gabès, Tunisia). Samples were collected once from 34 stations, while seasonal variations were studied by sampling four times at 12 stations over the period 2013-2014. A total of 159 macrobenthos taxa associated with intertidal Zostera noltei beds are identified from the 34 stations, with a taxonomic dominance of crustaceans (32%), molluscs (29%) and annelids (27%). Abundance varies from 9244 to 36,844 ind・m−2 with a mean value of 14,346 ind・m−2. Analysis of the trophic structure shows that the majority of stations are strongly represented by carnivores (41%), followed by the non-selective deposit feeders (16%). Cluster analysis and multidimensional scaling allow identification of three main benthic assemblages based on species abundance, corresponding to different sediment types and organic matter contents. The seasonal variability in abundance, diversity and community structure is mainly due to spring and summer recruitment. The biotic indices (i.e. AMBI, BO2A and BENTIX) show that the intertidal area of Kneiss Islands exhibits a good ecological status.

International audience; The polychaete Sabellaria alveolata (Linnaeus, 1767) is an important ecosystem engineer building reef structureswhich add to the topographic complexity in colonized areas. In Europe, the most extensive reef formation is located in the Bay of Mont-Saint-Michel (France). Since 2006, Sabellaria bio-constructions have developed on hard substrates along the west coast of the Cotentin Peninsula between Champeaux and Saint-Germain-sur-Ay on the northern part of the Bay of Mont-Saint-Michel. In this sector, two distinct types of bio-construction can be distinguished: platforms and reefs. The aim of this study is to analyse the patterns of the associated macrofauna on these platforms and reefs, as well as outside, and test for a correlation between the presence of Sabellaria bio-constructions and the richness of the benthic macrofauna. Univariate analyses are used to compare the macrofauna on four sites (Champeaux, Lingreville, Blainville-sur-Mer and Saint-Germain-sur-Ay). The results show a higher taxonomic richness on the platform-type than on the reef-type structures, and also a higher taxonomic richness outside the bio-construction areas. This suggests that, on the examined sites, the presence of S. alveolata bio-constructions does not contribute to higher levels of benthic macrofaunal richness on hard substrates. Temporary bio-constructions along this coast exhibit reefs of interest at some sites as well as in very small zones which merit special attention.

International audience; The Gulf of Gabès in southern Tunisia shows the highest tidal ranges of the Mediterranean Sea. During spring tides, the very large intertidal sand and mudflat zone is exploited for clam harvesting, mainly targeted on the species Ruditapes spp. mainly Ruditapes decussatus by Linnaeus in 1758. To assess the short-term impact of clam harvesting on the intertidal macrobenthos of the Kneiss Islands mudflats, a control-impact study was set up in September and December 2013 using a BACI (Before-After-Control-Impact) design, with a control station and eight stations fished for clams. Significant decreases in total macrofauna, benthic polychaetes (mainly Nephtyidae, Eunicidae, Spionidae, Maldanidae, Sabellidae and Cirratulidae) and R. decussatus were observed from before to after the harvesting initiated. In the future, it would be very important to control this human activity, due to its negative impact on the surrounding macrofauna, which represent essential prey for fishes and birds living in this protected area.

Along the French coast of the English Channel, Hemigrapsus sanguineus (De Haan, 1835) is abundant under boulders on exposed shores that have high-energy hydrodynamic conditions in the intertidal zone. However, small individuals (< 6 mm) are rare in the muddy gravel sediments under boulders and the settlement habitat for post-larvae is largely unknown. This study explored whether mussel beds could represent a settlement zone for H. sanguineus . At the end of the summer of 2013, there were many post-larvae and small crabs in some mussel beds, with up to 528 individuals/m². However, at one location, no juveniles of H. sanguineus were found in mussel bed habitat despite the presence of adults on the same shore. We conclude that mussel beds are an important habitat for the settlement of juvenile crabs. Key words: Asian shore crabs, invasive marine species, English Channel Introduction The introduction of alien shore crabs into coastal environments is mainly the result of human activities that are becoming more frequent with the ever-increasing maritime traffic levels (Williams 1984; Ng et al. 2008). Nevertheless, the introduction of invasive species is a complex phenomenon, and there is a pressing need to assess the risks linked to biological invasions. In some cases, the introduced species can have a strong negative, or even a positive, effect on native species and/or communities (Carlton 1989; Ruiz et al. 1997; Cohen and Carlton 1998; Occhipinti-Ambrogi 2007). The Asian shore crab

Recreational and professional clam fishing was an important activity on the extensive intertidal zone of the western Cotentin coast (western English Channel). A variety of fishing gear was used to harvest the target species: the European clam Ruditapes decussatus (Linnaeus, 1758) and the introduced Manila clam R. philippinarum (Adams and Reeve, 1850). In this study, we studied the effect of rake harvesting during the spring tides of February–March 2014, following an experimental design with a control station and three stations impacted by rake harvesting in three sediment types: sandy, gravelly, and mixed gravelly rocky habitats. No significant sediment and macrofauna changes occurred at the three sites after rake harvesting. Nevertheless, the number of clams decreased significantly after raking on the gravelly habitat, whereas in the other two habitats, sediment transport in this high-energy hydrodynamic environment was able to transfer clams and other macrofauna species across the fishing sites, thus minimizing the effects of rake harvesting. Therefore, although the effect of rake harvesting appeared limited during winter, the regional impact (high fishing pressure along 60 km of coast) and increase of recreational fishers during summer needed to be studied in the future.

International audience; The Chinese mitten crab Eriocheir sinensis H. Milne Edwards, 1853 is a native crab of East Asia. It is predominant in freshwater but migrates seawards to breed. It was found in Normandy, for the first time, in 1943 (Hoestlandt, 1943, 1948). Seventy-one years of observations along the Normandy coast and in the Seine estuary, as well as in the ship-canals and inner seaport of Le Havre, have recorded a total of 65 crabs at 33 locations. The observation of an E. sinensis juvenile in mussel beds along the Calvados coast indicates that this habitat can be a favourable location for larval settlement.

International audience; Comprehending marine invasions requires a better knowledge of the biological traits of invasive species, and the future spread of invasive species may be predicted through comprehensive overviews of their distribution. This study thus presents the current distribution of a non-indigenous species, the Asian shore crab Hemigrapsus takanoi, as well as the species population characteristics (size distribution and cohorts), based on a five-year survey (2008e2012) along the French coast of the English Channel. Two large populations were found near harbours: one on the Opal Coast (where density reached 61 ! 22 ind.m"2, mean ! s.d., in Dunkirk harbour) and one on the Calvados coast (density up to 26 ! 6 ind.m"2, mean ! s.d, in Honfleur harbour). H. takanoi exhibited a short life cycle, a rapid growth, an early sexual maturity and a high adult mortality. These features, combined with previously described high fecundity and high dispersal ability, endow this species with an 'r-selected strategy'. This strategy, which usually characterises species with a high colonisation ability, would explain the success of H. takanoi for colonising the French coast of the Channel. However, the species was found only in harbours and their vicinity; H. takanoi thus exhibited a discontinuous distribution along the 700 km of coastline. These results are discussed regarding sediment preference and potential introduction vectors. Hemigrapsus takanoi is now considered as established on the French coast and further studies are needed to evaluate the consequences of its introduction on the structure and functioning of the impacted shores

International audience; The freshwater discharge into the Seine estuary decreased between 1996 and 2012 and no discharge N 1200 m3 s−1 has occurred after 2001. The suprabenthic community in the navigational channel ofthe Seine estuary was characterised in 1996 by high abundances and biomass of mysids and the decapod Palaemon longirostris, which were among the highest in the world for transitional waters during a period of high discharge of the Seine River. A recent sampling (2011-2012) of the suprabenthos in new hydrological conditions (i.e., lowriver discharge) showed subsequent changes of the quantitative composition of the community with both decreases of abundance and biomass. Such long-term changes were probably due to the combination of hydrological changes, and anthropogenic modifications of the entrance of the Estuary, the Port 2000 construction, and supplementary dredging in the navigational channel of the Rouen harbour. The changes of the suprabenthic community encompassed an important impact in the estuarine trophic chain, which was essential to fish juveniles, such as sea bass and flat fish.

International audience; The invasion process can be described as a succession of stages initiated by the transport of organisms from their native range to a new area where they persist, proliferate and spread. It is important to monitor the demographic development of invaders for management purposes. This study focuses on the different stages of population development during the invasion process and underlines the importance of understanding and monitoring the 'persistence phase'. The distribution of Hemigrapsus sanguineus (Asian shore crab) in the English Channel, along the French coast, was first undertaken in 2008. In 2010, 35 sites were surveyed and it appeared that the abundance of this species had already established a 2-5 fold increase since 2008. The present study presents the geographical distribution of H. sanguineus in 2011 and 2012 which includes a further 39 sites (72 sampling stations in 2012). All populations observed during previous years persisted in 2011 and 2012. In 2012, H. sanguineus was detected at 61 sites; 36 intensely colonised (including 3 newly colonised sites compared to 2011); 22 had trace numbers and 3 sites had 'proven presence'. In addition to males with carapaces up to 39 mm width (CW), abundances increased by a factor of 2 since 2010, which testifies for the naturalized status of the species along the French coast of the English Channel. Since 2008, La Hougue proved to be the most abundantly colonised site along the French coast. By 2011 it had an average density of 101±19 ind.m-2, with an abundance of 258±54 individuals (under 30 boulders). Populations were subsequently halved in 2012. Increasing densities and abundances recorded between 2008 and 2011 at la Hougue suggest that H. sanguineus had reached the 'expansion phase', but the dynamics of H. sanguineus populations at the most colonised sites (12 sampling sites with abundance >200 individuals under 30 boulders), suggest that maximum values had already peaked and that the 'persistence phase' was probably reached. The implementation of pluri-annual surveys seems of prime importance to correctly evaluate population dynamics of alien species.