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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

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.