Search

21 pages, 4 figures, 1 table, supporting information https://doi.org/10.1002/ece3.9740.-- Data Availability Statement: Raw RNA-seq data and mt-mutS sequences have been uploaded to NCBI's SRA (BioProject ID: PRJNA847883) and GenBank databases (Accessions numbers: ON804207-ON804214), respectively. Final sequence alignments and microsatellite data are available on DRYAD (https://doi.org/10.5061/dryad.r7sqv9sfm), The accurate delimitation of species boundaries in nonbilaterian marine taxa is notoriously difficult, with consequences for many studies in ecology and evolution. Anthozoans are a diverse group of key structural organisms worldwide, but the lack of reliable morphological characters and informative genetic markers hampers our ability to understand species diversification. We investigated population differentiation and species limits in Atlantic (Iberian Peninsula) and Mediterranean lineages of the octocoral genus Paramuricea previously identified as P. clavata. We used a diverse set of molecular markers (microsatellites, RNA-seq derived single-copy orthologues [SCO] and mt-mutS [mitochondrial barcode]) at 49 locations. Clear segregation of Atlantic and Mediterranean lineages was found with all markers. Species-tree estimations based on SCO strongly supported these two clades as distinct, recently diverged sister species with incomplete lineage sorting, P. cf. grayi and P. clavata, respectively. Furthermore, a second putative (or ongoing) speciation event was detected in the Atlantic between two P. cf. grayi color morphotypes (yellow and purple) using SCO and supported by microsatellites. While segregating P. cf. grayi lineages showed considerable geographic structure, dominating circalittoral communities in southern (yellow) and western (purple) Portugal, their occurrence in sympatry at some localities suggests a degree of reproductive isolation. Overall, our results show that previous molecular and morphological studies have underestimated species diversity in Paramuricea occurring in the Iberian Peninsula, which has important implications for conservation planning. Finally, our findings validate the usefulness of phylotranscriptomics for resolving evolutionary relationships in octocorals, This work was funded by program BIOMARES, a Pew Marine Fellowship, and FCT – Foundation for Science and Technology UIDB/04326/2020, UIDP/04326/2020, LA/P/0101/2020, PTDC/BIA-CBI/6515/2020; EU-BiodivERsA BiodivRestore-253 (FCT: DivRestore/0013/2020); EU Horizon 2020 research and innovation program (MERCES: Grant no. 689518); as well as the Inaqua Conservation Fund (Oceanário de Lisboa and National Geographic Channel) and National Geographic Society/Waitt Grant no. W153-11. This article is also a product of the French network on Marine Connectivity (GDR MarCo). M.C. was supported by postdoctoral fellowships of projects HABMAR (Grant no. MAR-01.04.02-FEAMP-0018) co-financed by the European Maritime and Fisheries Fund of the Operational Program MAR 2020 for Portugal (Portugal 2020), and BiodivAMP (Grant no. FA_06_2017_045) financed by the Directorate-General for Sea Policy of the Ministry of Economy and Sea for Portugal under the Operational Program Fundo Azul. JBL was funded by assistant researcher contract framework of the RD Unit—UID/Multi/04423/2019 – Interdisciplinary Centre of Marine and Environmental Research—financed by the European Regional Development Fund (ERDF) through COMPETE2020—Operational Program for Competitiveness and Internationalization (POCI) and national funds through FCT/MCTES (PIDDAC). JB was funded by a FCT PhD scholarship SFRH/BD/72501/2010, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

The octocoralParamuricea clavatais an ecosystem architect of the Mediterranean temperate reefs that is currently threatened by episodic mass mortality events related to global warming. Local average thermal regimes nor recent thermal history have been shown to play a significant role in population thermotolerance in this species. The microbiome, however, may play an active role in the thermal stress susceptibility of corals, potentially holding the answer as to why corals show differential sensitivity to heat-stress. To investigate this, the prokaryotic and eukaryotic microbiome ofP. clavatacollected from around the Mediterranean was characterized before experimental heat-stress to determine if its microbial composition influences the thermal response of the holobiont. We found that the prokaryotic community was not informative in predicting the thermal susceptibility ofP. clavata. On the other hand, members ofP. clavata’smicroeukaryotic community were significantly correlated with thermal stress sensitivity. Syndiniales from theDino-Group I Clade 1were significantly enriched in thermally resistant corals, while the apicomplexan corallicolids were significantly enriched in thermally susceptible corals. Corallicolids are associated with 70% of coral genera around the world, yet the ecological role of this general anthozoan symbiont has yet to be determined. We hypothesize thatP. clavatamortality following heat-stress may be caused by a shift from apparent commensalism to parasitism in the corallicolid-coral host relationship driven by the added stress. Our results show the potential importance of corallicolids and the rest of the microeukaryotic community of corals to understanding thermal stress response in corals and provides a useful tool to guide conservation efforts and future research into coral-associated microeukaryotes.

14 pages, 5 figures, 1 table, supporting information https://doi.org/10.1111/ele.13718.-- Data availability statement: The data and code related to the manuscript have been placed in the Dryad Digital Repository: https://doi.org/10.5061/dryad.69p8cz91g, Quantifying changes in functional community structure driven by disturbance is critical to anticipate potential shifts in ecosystem functioning. However, how marine heatwaves (MHWs) affect the functional structure of temperate coral‐dominated communities is poorly understood. Here, we used five long‐term (> 10 years) records of Mediterranean coralligenous assemblages in a multi‐taxa, trait‐based analysis to investigate MHW‐driven changes in functional structure. We show that, despite stability in functional richness (i.e. the range of species functional traits), MHW‐impacted assemblages experienced long‐term directional changes in functional identity (i.e. their dominant trait values). Declining traits included large sizes, long lifespans, arborescent morphologies, filter‐feeding strategies or calcified skeletons. These traits, which were mostly supported by few sensitive and irreplaceable species from a single functional group (habitat‐forming octocorals), disproportionally influence certain ecosystem functions (e.g. 3D‐habitat provision). Hence, MHWs are leading to assemblages that are deficient in key functional traits, with likely consequences for the ecosystem functioning, We acknowledge the funding of the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019‐000928‐S). This research has also been partially funded by the HEATMED project (RTI2018‐095346‐B‐I00, MCIU/AEI/FEDER, UE), Interreg Med Programme (Projects MPA‐ENGAGE; 5216 | 5MED18_3.2_M23_007 and MPA‐Adapt, 1MED15_3.2_M2_337) 85% cofunded by the European Regional Development Fund, the MIMOSA project funded by the Foundation Prince Albert II Monaco, the Perfect project funded by the TOTAL Foundation, the Medchange project funded by the Agence Nationale pour la Recherche (ANR) and the European Union's Horizon 2020 research and innovation programme under grants agreements 689518 (MERCES) and SEP‐210597628 (FutureMARES). D.G.G. is supported by an FPU grant (FPU15/05457) from the Spanish Ministry of Education. CL gratefully acknowledges the financial support by ICREA under the ICREA Academia programme. VB is supported by the Templeton Foundation (grant #60501, ‘Putting the Extended Evolutionary Synthesis to the Test’). J‐B.L is supported by the strategic Funding UIDB/04423/2020 and UIDP/04423/2020. [...] D.G.G, C.L, J‐B.L, N.B, P.L.S & J.G are part of the Marine Conservation research group (www.medrecover.org) (2017 SGR 1521) from the Generalitat de Catalunya.

Este artículo contiene 18 páginas, 4 figuras., Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we show that during the 2015–2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning. Overall, we show that increasing the resolution of empirical observation is critical to enhancing our ability to more effectively understand and manage the consequences of climate change., This paper was supported by Euromarine. Joaquim Garrabou acknowledges the funding by the “Severo Ochoa Centre of Excellence” (CEX2019-000928-S), the MCIU/AEI/FEDER [HEATMED; RTI2018-095346-B-I00], Interreg-Med Programme MPA-Engage (1MED15_3.2_M2_337), the European Union Horizon 2020 research and innovation programme (Futuremares SEP-210597628). Nuria Teixido acknowledges the French National Research Agency (4Oceans-MOPGA grant, ANR-17-MPGA-0001) and internal funds from the Stazione Zoologica Anton Dohrn. Gil Rilov was supported by the Israel Ministry of Environmental Protection. Hocein Bazairi, Free Spinosa, and Vasilis Gerovasileiou acknowledge the funding by the MAVA Fondation (MedKeyHabitats I Project) and the European Commission (Ecap-MED II Project; projects implemented by UNEP/MAP-RAC/SPA). Alfonso Ramos was supported the CIESM “Tropical Signals,” Stelios Katsanevakis and Maria Sini were supported by the Project “Coastal Environment Observatory and Risk Management in Island Regions AEGIS+” (MIS 5047038), implemented within the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014–2020), co-financed by the Hellenic Government (Ministry of Development and Investments) and the European Union (European Regional Development Fund, Cohesion Fund), Stelios Katsanevakis, Maria Sini and Vasilis Gerovasileiou acknowledge the support of the MARISCA Project, co-funded by 85% by the EEA GRANTS, 2009–2014, and 15% by the Public Investments Programme (PIP) of the Hellenic Republic. Ivan Guala and Daniele Grech thanks thank the support of the project “Pinna nobilis—ricerca per la sopravvivenza: un'iniziativa di Citizen Science per tracciare la mortalità di massa di Pinna nobilis in Sardegna” project and the L/7 grant (CUP 87G17000070002) funded by the Regione Autonoma Sardegna. Jean-Baptiste Ledoux was funded by an assistant researcher contract framework of the RD Unit—UID/Multi/04423/2019—Interdisciplinary Centre of Marine and Environmental Research—financed by the European Regional Development Fund (ERDF) through COMPETE2020—Operational Program for Competitiveness and Internationalization (POCI) and national funds through FCT/MCTES (PIDDAC). This research was supported by the Strategic Funding UIDB/04423/2020 and UIDP/04423/2020 through national funds provided by the FCT—Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the program PT2020. Bernat Hereu and Cristina Linares acknowledge the support of the long-term monitoring programme of the catalan Natural Parks, funded by the Departament de Territori i Sostenibilitat of the Generalitat de Catalunya. Cristina Linares acknowledges the support of the ICREA Academia programme. David Díaz acknowledges the support the research grant CTM2016-77027-R of the Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad and Program of Marines Strategies of Spain funded by MITERD. Jamila Ben Soussi was partially funded by the Fondation Albert 2 Monaco (MIMOSA Project) and the Tropical Signals Program of CIESM. Giovanni Chimienti was supported by the Italian Ministry of Education, University and Research (PON 2014–2020, AIM 1807508–1, Linea 1), by the Ente Parco Nazionale del Gargano (Research agreement with CoNISMa N. 21/2018), and by the National Geographic Society (Grant EC-176R-18). Nathaniel Bensoussan acknowledges financial support from the European Commission through the programme “Caroline Herschell” in the context of the action “Developing Downstream applications and services on BIO-PHYsical characterization of the seascape for COASTal management” (BIOPHYCOAST). Monica Montefalcone and Annalissa Azzola collected some of their data on MMEs in the frame of the project “Mare Caldo” funded by Greenpeace Italy. Núria Marbà acknowledges financial support from the Spanish Ministries of Economy and Competitiveness (CTM2012-32603, CGL2015-71809-P) and Ministerio de Ciencia, Innovación y Universidades (RTI2018-095441-B-C21). Diego K. Kersting acknowledges support by the postdoctoral fellowship programme Beatriu de Pinós funded by the Secretary of Universities and Research (Government of Catalonia) and the Horizon 2020 programme of research and innovation of the European Union under the Marie Sklodowska-Curie grant agreement No 801370.

20 pages, 5 figures, 4 tables, supporting information https://doi.org/10.1111/ddi.13382.-- Data availability statement: Microsatellite genotypes are available on Dryad (DOI https://doi.org/10.5061/dryad.xgxd254gw), Aim: How historical and contemporary eco-evolutionary processes shape the patterns of genetic diversity and differentiation across species’ distribution range remains an open question with strong conservation implications. Focusing on the orange stony coral, Astroides calycularis, we (a) characterized the pattern of neutral genetic diversity across the distribution range; (b) gave insights into the underlying processes; and (c) discussed conservation implications with emphasis on a national park located on a hotspot of genetic diversity. Location: South Mediterranean Sea and Zembra National Park. Methods: We combined new data from 12 microsatellites in 13 populations located in the Centre and in the Western Periphery of the distribution range with a published dataset including 16 populations from the Western and Eastern Peripheries. We analysed the relationship among parameters of genetic diversity (He, Ar(g)) and structure (population-specific FST) and two measures of geographic peripherality. We compared two estimators of pairwise genetic structure (GST, DEST) across the distribution range. The evolutionary and demographic history of the populations following the Last Glacial Maximum was reconstructed using approximate Bayesian computations and maximum-likelihood analyses. We inferred the contemporary connectivity among populations from Zembra National Park and with the neighbouring area of Cap Bon. Results: We demonstrate a decrease in genetic diversity and an increase in genetic differentiation from the Centre to the Eastern and Western Peripheries of the distribution range. Populations from Zembra show the highest genetic diversity reported in the species. We identified a spillover effect towards Cap Bon. Main conclusions: The patterns of genetic diversity and differentiation are most likely explained by “the postglacial range expansion hypothesis” rather than the “central–peripheral hypothesis.” Enforcement of conservation measures should be considered to protect this genetic diversity pattern, in particular when considering the low effective population size inferred at many sites, JBL was funded by a Postdoctoral Grant (SFRH/BPD/74400/2010) from the Portuguese Foundation for Science and Technology (FCT). This research was supported by national funds through FCT within the scope of UIDB/04423/2020 and UIDP/04423/2020 and by the MIMOSA project funded by the Foundation Prince Albert II Monaco. JG, DGG and PL acknowledge the funding of the Spanish government through the “Severo Ochoa Centre of Excellence” accreditation (CEX2019-000928-S). This work was partially supported by the European Union's Horizon 2020 research and innovation program under grant agreement SEP-210597628 (FutureMARES)

Climate change is one of the biggest emerging threats to marine biodiversity in the Mediterranean Sea. In this chapter, we focus on the recurrent and large scale mass mortality events (MMEs) induced by marine heatwaves (MHWs), and their immediate and long-term impacts on structural octocorals from highly diverse coralligenous communities. By combining an accurate characterization of present and expected thermal stress conditions in coastal seawater from the surface down to 40 m depth with the state of the art on demography, population genetics, and responses to thermal stress, we analyze the ongoing eco-evolutionary impacts and explore future trajectories of these emblematic Mediterranean communities.

Este artículo contiene 13 páginas, 1 tabla, 5 figuras., Climate change threatens coastal benthic communities on a global scale. However, the potential effects of ongoing warming on mesophotic temperate reefs at the community level remain poorly understood. Investigating how different members of these communities will respond to the future expected environmental conditions is, therefore, key to anticipating their future trajectories and developing specific management and conservation strategies. Here, we examined the responses of some of the main components of the highly diverse Mediterranean coralligenous assemblages to thermal stress. We performed thermotolerance experiments with different temperature treatments (from 26 to 29°C) with 10 species from different phyla (three anthozoans, six sponges and one ascidian) and different structural roles. Overall, we observed species‐specific contrasting responses to warming regardless of phyla or growth form. Moreover, the responses ranged from highly resistant species to sensitive species and were mostly in agreement with previous field observations from mass mortality events (MMEs) linked to Mediterranean marine heat waves. Our results unravel the diversity of responses to warming in coralligenous outcrops and suggest the presence of potential winners and losers in the face of climate change. Finally, this study highlights the importance of accounting for species‐specific vulnerabilities and response diversity when forecasting the future trajectories of temperate benthic communities in a warming ocean., the funding support of Organismo Autónomo Parques Nacionales (CORCLIM 759S/2012 and 766S/2012), the TOTAL foundation (CLIMCARES project), the Prince Albert II de Monaco Foundation (MIMOSA project n° 1983), the MPA‐ADAPT project, the Interreg MED Program (European Regional Development Fund), and the European Union's Horizon 2020 research and innovation program under grant agreement No 689518 (MERCES). D.G.G. was supported by an FPU grant (FPU15/05457) from the Spanish Ministry of Education, M.P.E. by an APIF‐2016 and I.M.S. by an FPI grant (BES‐2013‐066150). The authors are part of the Marine Conservation research group (www. medrecover.org) (2017 SGR 1521) from the Generalitat de Catalunya.

12 pages, 5 figures, 6 tables, supplemental material https://doi.org/10.25387/g3.12640691, The octocoral, Paramuricea clavata, is a habitat-forming anthozoan with a key ecological role in rocky benthic and biodiversity-rich communities in the Mediterranean and Eastern Atlantic. Shallow populations of P. clavata in the North-Western Mediterranean are severely affected by warming-induced mass mortality events (MMEs). These MMEs have differentially impacted individuals and populations of P. clavata (i.e., varied levels of tissue necrosis and mortality rates) over thousands of kilometers of coastal areas. The eco-evolutionary processes, including genetic factors, contributing to these differential responses remain to be characterized. Here, we sequenced a P. clavata individual with short and long read technologies, producing 169.98 Gb of Illumina paired-end and 3.55 Gb of Oxford Nanopore Technologies (ONT) reads. We obtained a de novo genome assembly accounting for 607 Mb in 64,145 scaffolds. The contig and scaffold N50s are 19.15 Kb and 23.92 Kb, respectively. Despite of the low contiguity of the assembly, its gene completeness is relatively high, including 75.8% complete and 9.4% fragmented genes out of the 978 metazoan genes contained in the metazoa_odb9 database. A total of 62,652 protein-coding genes have been annotated. This assembly is one of the few octocoral genomes currently available. This is undoubtedly a valuable resource for characterizing the genetic bases of the differential responses to thermal stress and for the identification of thermo-resistant individuals and populations. Overall, having the genome of P. clavata will facilitate studies of various aspects of its evolutionary ecology and elaboration of effective conservation plans such as active restoration to overcome the threats of global change, We acknowledge the funding support of the European Union’s Horizon 2020 research and innovation program under grant agreement No 689518 (MERCES) and the Strategic Funding UID/Multi/04423/2013 through national funds provided by FCT – Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020. JBL is funded by an assistant researcher contract framework of the RD Unit - UID/Multi/04423/2019 - Interdisciplinary Centre of Marine and Environmental Research – financed by the European Regional Development Fund (ERDF) through COMPETE2020 - Operational Program for Competitiveness and Internationalisation (POCI) and national funds through FCT/MCTES (PIDDAC). AA was partially supported by the FCT project PTDC/CTA-AMB/31774/2017 (POCI-01-0145-FEDER/031774/2017). DGG was supported by an FPU grant (FPU15/05457) from the Spanish Ministry of Education. We acknowledge support of the Spanish Ministry of Science and Innovation to the EMBL partnership, the Centro de Excelencia Severo Ochoa, the CERCA Programme / Generalitat de Catalunya, the Spanish Ministry of Science and Innovation through the Instituto de Salud Carlos III, the Generalitat de Catalunya through Departament de Salut and Departament d'Empresa i Coneixement, and the Co-financing by the Spanish Ministry of Science and Innovation with funds from the European Regional Development Fund (ERDF) corresponding to the 2014-2020 Smart Growth Operating Program. JBL and JG planned and granted the funding to start the project, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

12 pages, 6 figures, 1 table, supporting information https://doi.org/10.1002/aqc.3236, 1. Marine ecosystems are highly affected by several human stressors. In this context, beyond passive restoration measures such as the creation of marine protected areas, it is urgent that we explore active restoration measures to enhance and accelerate the recovery of sessile marine species. 2. Bryozoans are among the most common sessile invertebrates in rocky bottom ecosystems and are considered habitat‐forming species that are highly vulnerable to physical disturbances, such as recreational diving, ghost fishing nets, and global warming, which makes them highly vulnerable to other impacts. Despite their ecological importance and vulnerability, to date restoration actions for bryozoans have rarely been explored. 3. In this study, different restoration techniques were developed and tested, with a focus on two types of effective methodologies previously applied to other marine invertebrates: recruitment enhancement and the transplantation of adult colonies, in both cases using the Mediterranean bryozoan Pentapora fascialis as a model species. 4. First, different types of artificial surfaces were installed in different coralligenous habitats to test the enhancement of recruitment, concluding that plastic grids are the best substrate in terms of facilitating the recruitment of new bryozoan colonies. 5. Second, different methodologies were tested for adult transplantation. The most successful was to fix colonies to a suitable substrate with a nylon thread attached to the colony ex situ (i.e. on the boat). 6. Using this technique a trial restoration programme was undertaken, involving transplanting adult colonies collected from a ghost fishing net trapped on the bottom, which showed a high survival rate of ~50% after 6 months. 7. The low economic cost of the implementation of the proposed techniques as well as the successful results obtained highlight the viability of restoring bryozoan populations over long temporal and spatial scales, This study was partially funded by the ‘Parc Natural del Montgrí, Illes Medes i Baix Ter' and the ‘Departament de Territori i Sostenibilitat' of the Catalan Government project, the SMART project (CGL2012‐32194), and the European Union's Horizon 2020 research and innovation programme under grant agreement no. 689518 (MERCES). [...] All authors are part of the Marine Conservation research group (2017 SGR 1521) funded by ‘Generalitat de Catalunya'. MPE was supported by an ‘Ajuts de Personal Investigador predoctoral en Formació' (APIF) grant (APIF2016) and DGG was supported by a ‘Formación del Profesorado Universitario' (FPU) grant (FPU15/05457), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

The octocoral, Paramuricea clavata, is a habitat-forming anthozoan with a key ecological role in rocky benthic and biodiversity-rich communities in the Mediterranean and Eastern Atlantic. Shallow populations of P. clavata in the North-Western Mediterranean are severely affected by warming-induced mass mortality events (MMEs). These MMEs have differentially impacted individuals and populations of P. clavata (i.e. varied levels of tissue necrosis and mortality rates) over thousands of kilometers of coastal areas. The eco-evolutionary processes and genetic factors contributing to these differential responses remain to be characterized. Here, we sequenced a P. clavata individual with short and long read technologies, producing 169.98 Gb of Illumina paired-end and 3.55 Gb of Oxford Nanopore Technologies (ONT) reads. We obtained a de novo hybrid assembly accounting for 712.4 Mb and 107,682 scaffolds. The contig and scaffold N50 are 15.85 Kb and 17.01 Kb, respectively. Despite of the low contiguity of the assembly, the gene completeness was relatively high, including 86% of the 978 metazoan genes contained in the metazoa_odb9 database. A total of 76,508 protein-coding genes and 85,763 transcripts have been annotated. This assembly is one of the few octocoral genomes currently available. This is undoubtedly a valuable resource for characterizing the genetic bases of the differential responses to thermal stress and for the identification of thermo-resistant individuals and populations. Overall, the genome of P. clavata will help to understand various aspects of its evolutionary ecology and to elaborate effective conservation plans such as active restoration actions to overcome the threats of global change.

4th World Conference on Marine Biodiversity (WCMB 2018), 13-16 May 2018, Montreal, The temperate coralligenous bioconcretions are mainly built by the accumulation of encrusting coralline algae growing at low irradiance levels. They harbour approximately 10% of marine Mediterranean species (about 1600 species), including long-lived algae and invertebrates. Enhanced by climate change, several pressures affect coralligenous assemblages, leading to increased frequency of mass mortalities and dramatic loss of habitat complexity and biodiversity. The EU-funded project MERCES is developing innovative methodologies to restore macroinvertebrate habitat-forming species from three key taxonomic groups: Cnidaria/Anthozoa, Porifera/Demospongiae and Bryozoa. Restoration protocols are based on fragments/transplants from donor organisms and recruitment-enhancing devices. Collaboration with volunteers (divers and diving operators) in several phases of field activities proved crucial both to minimize underwater working time and to increase the sense of stewardship in a major users’ segment. Additionally, the MERCES project explores how to enhance restoration success by identifying the mechanisms conferring resistance to thermal stress in gorgonians. This is pursued by coupling thermotolerance experiments with next generation sequencing tools and facilitation processes (by comparing the outcomes of mono-specific vs. multi-specific transplanted assemblages). Results will be included in the strategic planning of restoration efforts in the Mediterranean in the context of global change

9 pages, 7 figures, supplementary information https://doi.org/10.1038/s41598-018-36094-9, Climate change threatens the structure and function of marine ecosystems, highlighting the importance of understanding the response of species to changing environmental conditions. However, thermal tolerance determining the vulnerability to warming of many abundant marine species is still poorly understood. In this study, we quantified in the field the effects of a temperature anomaly recorded in the Mediterranean Sea during the summer of 2015 on populations of two common sympatric bryozoans, Myriapora truncata and Pentapora fascialis. Then, we experimentally assessed their thermal tolerances in aquaria as well as different sublethal responses to warming. Differences between species were found in survival patterns in natural populations, P. fascialis showing significantly lower survival rates than M. truncata. The thermotolerance experiments supported field observations: P. fascialis started to show signs of necrosis when the temperature was raised to 25–26 °C and completely died between 28–29 °C, coinciding with the temperature when we observed first signs of necrosis in M. truncata. The results from this study reflect different responses to warming between these two co-occurring species, highlighting the importance of combining multiple approaches to assess the vulnerability of benthic species in a changing climate world, This study was partially funded by the “Parc Natural del Montgrí, Illes Medes i Baix Ter” and the “Departament de Territori i Sostenibilitat” of the Catalan Government project, the SMART project (CGL2012-32194) and the European Union’s Horizon 2020 research and innovation program under grant agreement No 689518 (MERCES). This output reflects only the author’s view and the European Union cannot be held responsible for any use that may be made of the information contained M.P.E was supported by an APIF grant (APIF2016), I.M.S by an FPI grant (BES-2013-066150), D.G.G by an FPU grant (FPU15/05457) and B.F by a SENACYT & STRI Postdoctoral Fellow (47-2017-4-FID16-239)