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Engineer species, such as gorgonians, provide several ecosystem services and play a significant role in the maintenance of biodiversity, which is why it is important to identify optimal strategies for their conservation. We aimed to test an ecological niche modelling approach in the marine shallow environment and identify the ecological niche of various species of gorgonians in order to lay the scientific foundation for future conservation actions. We analyzed a unique dataset of spatialized inventories on a regular grid (< 800 m) along 450 km of coastline of five gorgonian species commonly found in the Mediterranean shallow habitats (10-50 m deep). We replicated data collection in 2013 and 2020. Fourteen environmental predictors derived from the most advanced geomorphological and hydrological data were tested to assess the ecological niche of the five species using maximum entropy (MaxENT). We tested the sensitivity of the model fit to sampling bias by reducing the number of occurrences and their geographic extent. Our results showed that there was a difference in the spatial distribution of the five gorgonian species in the Gulf of Lion: Eunicella singularis and Leptogorgia sarmentosa were widely distributed while the occurrence of Paramuricea clavata, Corallium rubrum and Eunicella cavolini was limited. The model confirmed that depth, rugosity, slope, sea surface temperature, current and turbidity can be significant drivers for gorgonians distribution, but in different associations, enabling one to differentiate the niche of four of the five species. Moreover, the model did not always identify the species specific drivers suggested in previous studies. Despite the model identifying a similar niche for E. singularis and E. cavolini (based on the environmental predictors tested), the two species, in fact, displayed very different spatial distributions in the area. For all the species, except E. cavolini, the predicted suitable habitat distribution from our model matched the observed spatial distribution. The reduction of the number of presence observations did not alter the quality of the ecological niche models as long as the observation points were spread over the entire variability range of predictors. The latter can be achieved by only including presence observations from highly protected zones of the marine protected areas of the region. Our results provide a greater understanding of the factors shaping the distribution of five gorgonian species commonly found in Mediterranean shallow areas. This is an essential step in the development of spatial planning for marine biodiversity conservation aimed at these key engineering species and their resilience to climate change.

The natural mechanism for sessile species resilience after major population disturbance is larval dispersal during reproduction. Modelling larval dispersal when processes controlling dispersal are accounted for, is a powerful tool to anticipate connectivity patterns among populations. However, simulations performance might be altered considerably by either flow representation in the underlying hydrodynamical simulations or the inclusion of larval traits. Here, we assessed how behaviour, ocean model resolution and temporal variability in the ocean dynamics influence connectivity patterns among coastal rocky locations, some of them being designated as MPAs. We combined a fine (0.3 km) and coarser (1.5 km) resolution ocean model, with or without the negatively buoyant behaviour of Paramuricea clavata larvae, with different turbulence intensity, in three years and for pelagic larval duration (PLD) ranging from 1 to 28 days. Ocean model resolution was the most influential factor on the resulting connectivity levels. The results were also equally influenced by buoyancy, PLD and temporal variability, in the fine resolution configuration, while turbulence could be neglected. Based on these results, guidelines for coastal biophysical modelling are proposed.

Habitat-forming species sustain biodiversity and ecosystem functioning in harsh environments through the amelioration of physical stress. Nonetheless, their role in shaping patterns of species distribution under future climate scenarios is generally overlooked. Focusing on coastal systems, we assess how habitat-forming species can influence the ability of stress-sensitive species to exhibit plastic responses, adapt to novel environmental conditions, or track suitable climates. Here, we argue that habitat-former populations could be managed as a nature-based solution against climate-driven loss of biodiversity. Drawing from different ecological and biological disciplines, we identify a series of actions to sustain the resilience of marine habitat-forming species to climate change, as well as their effectiveness and reliability in rescuing stress-sensitive species from increasingly adverse environmental conditions.

In shallow environments, common unsteady flows, such as tides, waves or wind-driven currents modulate the diffusive boundary layer thickness that controls the exchange of electron acceptors for mineralization and oxidation processes in surficial sediment. This study demonstrated the ability of an oscillating grid mesocosm to (1) produce homogenous turbulence at the sediment-water interface of multiple sediment cores (between-core variability

International audience; Resuspension of microphytobenthic biomass that builds up during low tide has been acknowledged as amajor driver of the highly productive food web of intertidal mudflats. Yet, little is known about the contributionto pelagic food web of the resuspension of other microorganisms such as viruses, picoeukaryotes,cyanobacteria, bacteria, nanoflagellates, and ciliates, living in biofilms associated with microphytobenthosand surficial sediment. In the present study, a novel approach that involves simultaneous Lagrangian andEulerian surveys enabled to disentangle the effects of resuspension and mixing with offshore waters on thedynamics of water column microorganisms during a rising tide in the presence of waves. Temporal changesin the concentration of microorganisms present in the water column were recorded along a 3 km cross-shoretransect and at a fixed subtidal location. In both surveys, physical and biological processes were separated bycomparing the time-evolution of sedimentary particles and microorganism concentrations. During a risingtide, sediment erosion under wave action occurred over the lower and upper parts of the mudflat, whereerodibility was highest. Although erosion was expected to enrich the water column with the most abundantbenthic microorganisms, such as diatoms, bacteria and viruses, enrichment was only observed fornanoflagellates and ciliates. Grazing probably overwhelmed erosion transfer for diatoms and bacteria,while adsorption on clayed particles may have masked the expected water column enrichment in free virusesdue to resuspension. Ciliate enrichment could not be attributed to resuspension as those organisms wereabsent from the sediment. Wave agitation during the water flow on the mudflat likely dispersed gregariousciliates over the entire water column. During the rising tide, offshore waters imported more autotrophic,mainly cyanobacteria genus Synechococcus sp. than heterotrophic microorganisms, but this import was alsoheavily grazed. Finally, the water column became a less heterotrophic structure in the subtidal part of thesemi-enclosed bay, where mixing with offshore waters occurs (50% decrease), compared to the intertidalmudflat, when resuspension occurs. The present study suggests that this differential evolution resulted predominantlyfrom dilution with offshore waters less rich in heterotrophic microorganisms. Indeed, any inputof microorganisms accompanying physical transfers due to bed erosion or offshore water mixing was immediatelybuffered, probably to the benefit of grazers.

International audience; Repeated use of Cu based fungicides (Bordeaux mixture: Ca(OH)2+CuSO4) to control vine downy hasled to signi!cant increase of Cu in vineyard soils. In Mediterranean catchments, brief and intense flood events can multiply stream discharge by up to 10 and are responsible for important soil leaching and therefore for high "uxes of Cu exported at the outlet of the catchment. In order to assess the origin and fate of Cu measured in the Baillaury catchment (South of France, combined sequential extraction (SCE) and isotopic Cu compositions (δ65Cu) approaches are proposed in this study.

International audience

Un modèle numérique de couche limite oscillante a été développé sur la base de la fermeture turbulente k-w transitionnelle de Wilcox (1992) permettant de décrire des couches limites transitionnelles et turbulentes (programme européen SEDMOC). En modifiant les constantes de diffusion et de transition du modèle de Wilcox et en introduisant une condition de décollement de couche limite sous l'effet d'un gradient de pression adverse, on a pu reproduire avec un bien meilleur accord que le modèle originel de Wilcox des simulations directes (Vittori et Verzicco, 1998) ainsi que les mesures de Jensen et al. (1989) d'écoulement oscillant sur fond plat lisse dans le régime turbulent intermittent (version 1DV, Guizien et al., 2003). Ce modèle décrit également mieux que le modèle originel de Wilcox les grandeurs turbulentes mesurées dans l'interaction houle-courant par Dohmen-Janssen (1999) sur fond plat dans le régime turbulent rugueux (version 1DV, Guizien et al., 2003). En particulier, le modèle reproduit les fluctuations turbulentes lors de la décélération de l'écoulement ainsi que le déphasage des contraintes turbulentes sur la verticale. Ces deux points d'achoppement des modèles jusqu'alors expliquait en partie les difficultés des modèles existants à reproduire correctement les concentrations sédimentaires en présence de sédiment (Davies et al, 1997). Cette fermeture turbulente est également implémentée dans une version 2DHV du modèle qui permet d'étudier l'écoulement sur des fonds présentant des macro-rugosités. Il a été en particulier utilisé dans le cadre du programme européen SANDPIT pour calculer des profils de concentration en présence de formes de fond sédimentaires (ride de sable) et pour investiguer la notion de rugosité hydo-sédimentaire équivalente. La contribution du LOBB dans cette action transversale prévoyait les actions suivantes: - caractériser mathématiquement des rugosités d'origine biogène - modéliser l'hydrodynamisme pour une variété d'interaction houle-courant sur ces rugosités et paramétriser la rugosité macroscopique résultante (question 8) - comparer ces résultats avec ceux d'autres modèles numériques - tester la validité des simulations hydrodynamiques face aux expériences de laboratoire menées dans le cadre de ce projet (exemple des fonds de crépidules) - modélisation de la suspension sédimentaire pour ces mêmes fonds de crépidules pour des distributions granulométriques a) réalistes et b) idéales.

International audience; A new experimental procedure to generate solitary waves in a flume using a piston type wave maker is derived from Rayleigh's (1876, [18]) solitary wave solution. Resulting solitary waves fordimensionless amplitudes £ ranging from 0.05 to 0.5 are as pure as the ones generated using Goring's (1978, [7]) procedure which is based on Boussinesq (1871a, [1]) solitary wave, with trailing waves of amplitude lower than 3 % of the main pulse amplitude. In contrast with Goring's procedure, the new procedure results in very little loss of amplitude in the initial stage of the propagation of the solitary waves. We show that solitary waves generated using this new procedure are more rapidly established. This is attributed to the better description of the outskirts decay coefficient in a solitary wave given by Rayleigh's solution rather than by a Boussinesq expression. Two other generation procedures based on first-order (KdV) and second order shallow water theories are also tested. Solitary waves generated by the latter are of much lower quality than those generated with Rayleigh or Boussinesq-based procedures.

Habitat-forming species sustain biodiversity and ecosystem functioning in harsh environments through the amelioration of physical stress. Nonetheless, their role in shaping patterns of species distribution under future climate scenarios is generally overlooked. Focusing on coastal systems, we assess how habitat-forming species can influence the ability of stress-sensitive species to exhibit plastic responses, adapt to novel environmental conditions, or track suitable climates. Here, we argue that habitat-former populations could be managed as a nature-based solution against climate-driven loss of biodiversity. Drawing from different ecological and biological disciplines, we identify a series of actions to sustain the resilience of marine habitat-forming species to climate change, as well as their effectiveness and reliability in rescuing stress-sensitive species from increasingly adverse environmental conditions. EuroMarine - European Marine Research Network

Understanding the patterns of connectivity is required by the Strategic Plan for Biodiversity 2011–2020 and will be used to guide the extension of marine protection measures. Despite the increasing accuracy of ocean circulation modelling, the capacity to model the population connectivity of sessile benthic species with dispersal larval stages can be limited due to the potential effect of filters acting before or after dispersal, which modulates offspring release or settlement, respectively. We applied an interdisciplinary approach that combined demographic surveys, genetic methods (assignment tests and coalescent-based analyses) and larval transport simulations to test the relative importance of demographics and ocean currents in shaping the recent patterns of gene flow among populations of a Mediterranean gorgonian (Eunicella singularis) in a fragmented rocky habitat (Gulf of Lion, NW Mediterranean Sea). We show that larval transport is a dominant driver of recent gene flow among the populations, and significant correlations were found between recent gene flow and larval transport during an average single dispersal event when the pelagic larval durations (PLDs) ranged from 7 to 14 d. Our results suggest that PLDs that efficiently connect populations distributed over a fragmented habitat are filtered by the habitat layout within the species competency period. Moreover, a PLD ranging from 7 to 14 d is sufficient to connect the fragmented rocky substrate of the Gulf of Lion. The rocky areas located in the centre of the Gulf of Lion, which are currently not protected, were identified as essential hubs for the distribution of migrants in the region. We encourage the use of a range of PLDs instead of a single value when estimating larval transport with biophysical models to identify potential connectivity patterns among a network of Marine Protected Areas or even solely a seascape.

International audience; Climate‐induced threats are increasingly affecting marine populations worldwide. In the last few decades, several gorgonian species have been affected by mass mortality events in the north‐west Mediterranean, putatively linked to local sea temperature increases during heatwaves. For many benthic sessile species, recovery after disturbances depends upon larval supply shaping the connections among populations.In the Ligurian Sea, genetic analyses showed that some Paramuricea clavata populations recovered after mass mortality events; however, the patterns of connectivity, and the potential role of migration in supporting the recovery of the populations of P. clavata, across its distribution range within the Ligurian Sea are still unknown.In this study, the population genetic structure and migration patterns of P. clavata populations have been analysed across seven sites in the Ligurian Sea, some of which have been affected by mass mortality events.Evidence of a population bottleneck was found in most of the populations studied. Significant genetic differentiation was found among P. clavata populations, reflecting habitat fragmentation at a regional scale, except for two populations found 20 km apart. Continuing gene flow between distant populations was also revealed. Empirical data suggest that gene flow among populations may have contributed to support their recovery from mass mortality events.The study identified populations in the central part of the Ligurian Sea that can be strategic for the regional persistence of the species. These findings highlight that the preservation of key populations could maintain connectivity and gene flow in the metapopulation, and increase the resilience of the species.

Philippart, Catharina J.M. et al., Reproductive cycles of marine invertebrates with complex life histories are considered to be synchronized by water temperature and feeding conditions, which vary with season and latitude. This study analyses seasonal variation in the occurrence of oyster (Crassostrea gigas) and mussel (Mytilus edulis/. galloprovincialis) larvae across European coastal waters at a synoptic scale (1000s of km) using standardised methods for sampling and molecular analyses.We tested a series of hypotheses to explain the observed seasonal patterns of occurrence of bivalve larvae at 12 European stations (located between 37°N and 60°N and 27°W and 18°E). These hypotheses included a model that stated that there was no synchronisation in seasonality of larval presence at all between the locations (null hypothesis), a model that assumed that there was one common seasonality pattern for all stations within Europe, and various models that supposed that the variation in seasonality could be grouped according to specific spatial scales (i.e., latitude, large marine ecosystems and ecoregions), taxonomic groups, or several combinations of these factors.For oysters, the best models explaining the presence/absence of larvae in European coastal waters were (1) the model that assumed one common seasonal pattern, and (2) the one that, in addition to this common pattern, assumed an enhanced probability of occurrence from south to north. The third best model for oysters, with less empirical support than the first two, stated that oysters reproduced later in the south than in the north. For mussels, the best models explaining the seasonality in occurrence of larvae were (1) the model that assumed four underlying trends related to large marine ecosystems, and (2) the one that assumed one common seasonal pattern for larvae occurrence throughout Europe.Such synchronies in larval occurrences suggest that environmental conditions relevant to bivalve larval survival are more or less similar at large spatial scales from 100s to 1000s of km. To unravel the underlying mechanisms for this synchronisation is of particular interest in the light of changing environmental conditions as the result of global climate change and the possible consequences for marine food webs and ecosystem services. © 2012 Elsevier Ltd.