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Arsenic’s occurrence in the environment could be due to human activities as well as to natural sources. In this study, Posidonia oceanica and Cymodocea nodosa are collected in 84 sites around the Mediterranean basin. In addition, both seagrass are collected monthly, in two sites (Calvi in Corsica and Salammbô in Tunisia). Arsenic concentrations in C. nodosa present seasonal variations in relation with spring phytoplankton blooms. For both species arsenic concentration is higher in the vicinity of geological sources (mining), lagoon outlets and industrial activities. Moreover, Mediterranean islands (Balearic, Sardinia, Corsica, Malta, Crete and Cyprus) and the Southern basin coastline exhibit lower concentrations in Arsenic than the rest of the Mediterranean basin. The wide spread distribution of these two species would encourage their use in a global monitoring network devoted to Arsenic contamination.

Arsenic’s occurrence in the environment could be due to human activities as well as to natural sources. In this study, Posidonia oceanica and Cymodocea nodosa are collected in 84 sites around the Mediterranean basin. In addition, both seagrass are collected monthly, in two sites (Calvi in Corsica and Salammbô in Tunisia). Arsenic concentrations in C. nodosa present seasonal variations in relation with spring phytoplankton blooms. For both species arsenic concentration is higher in the vicinity of geological sources (mining), lagoon outlets and industrial activities. Moreover, Mediterranean islands (Balearic, Sardinia, Corsica, Malta, Crete and Cyprus) and the Southern basin coastline exhibit lower concentrations in Arsenic than the rest of the Mediterranean basin. The wide spread distribution of these two species would encourage their use in a global monitoring network devoted to Arsenic contamination., peer-reviewed

International audience

TunAlgoBase is a computerized database aiming to list tunisian macroalgae and store at the same place different species information such as taxonomy, biology, ecology, geographical distribution and potential use. Geographical distribution data are most complet for the 414 species in the database. The other headings such as taxonomy, biology, ecology,... are in continual enhancement and completed for some species. TunAlgoBase هي شبكة معطيات معلوماتية هدفها تقديم لائحة الطحالب القاعية المتواجدة بالسواحل التونسية، و خزن المعلومات الخاصة بتصنيف مختلف الأنواع، بيولوجيتها، إيكولوجيتها، توزيعها على السواحل التونسية و مجال استعمالها، بموقع واحد. تحتوي الشبكة حاليا على 414 نوع من الطحالب مع توزيعها الجيوغرافي. أما بالنسبة لبقية المعلومات كالتصنيف و البيولوجيا و الإيكولوجيا فهي متوفرة إلا لبعض الأنواع و ستستكمل الشبكة لاحقا. TunAlgoBase est une base de données informatisée qui a pour objectif de lister les macroalgues répertoriées en Tunisie et de stocker au niveau d’une même ressource des informations concernant les différentes espèces du point de vue de leur taxonomie, leur biologie, leur écologie, leur distribution géographique et leurs domaines d’utilisation. La base contient actuellement 414 espèces. Pour toutes les espèces répertoriées, la distribution géographique est disponible. Les autres rubriques telles que la taxonomie, la biologie, l’écologie,... en cours d’enrichissement, ne sont disponibles que pour certaines espèces. Published Database; Base de données informatisées; TunAlgoBase; biodiversité; macroalgues

قمنا في هذا البحث باستخلاص عدد من الصابونيات من صنف من اصناف خيار البحر المتواجدة ببحيرة بنزرت وهي (اولوتيغيا تيبيلوزا) وتمت دراسة هذه المواد المستخلصة حسب مرحلة النضوج الجنسي و تم كذلك اثبات ان هذا المستحضر ذو مفعول بيولوجي اذ تسبب في انحلال كريات الدم الحمراء Suite à une séparation par chromatographie sur couche mince plusieurs types de saponines ont été mis en évidence dans les extraits partiellement purifiés d’ de la lagune de Bizerte. Ces composés paraissent quantitativement différents selon la période sexuelle et présentent une importante activité hémolytique qui dépend de la concentration de l’extrait ainsi que de la durée de son incubation avec les globules rouges. Following a separation by thin layer chromatography we demonstrate the presence of several types of saponins in partially purified extracts of of the Bizerte lagoon. These compounds appear quantitatively different according to the sexual period. Saponins of present an important hemolytic activity. Published Holothuria tubulosa

Depuis sa parution en Méditerranée nord occidentale en 1984, l’algue verte d’origine tropicale Caulerpa taxifolia n’a pas cessé de progresser le long du littoral septentrional de la Méditerranée. Le présent travail signale pour la première fois la présence de cette algue sur le littoral oriental de la Méditerranée et plus précisément dans la rade de Sousse (Tunisie), en face du port, par 17 mètres de profondeur. L’arrivée de Caulerpa taxifolia à Sousse, n’est certainement pas le résultat d’une progression naturelle à partir d’anciennes station, l’hypothèse la plus probable expliquant son existence dans la rade serait son introduction liée à un transport de boutures par des embarcations ayant auparavant jeté l’encre dans des zones déjà envahies par l’espèce. Since its appearence in north west of Mediterranean sea in 1984, the green tropical seaweed Caulerpa taxifolia has nt ceased to progress along the northern coast of the Mediterranean. The present work signals for the first time the presence of this seaweed on the littoral oriental of the Mediterranean and more precisely in the roadstead of Sousse (Tunisia), in front of the harbour, by 17 meters depth. The arrival of Caulerpa taxifolia to Sousse, is certainly not the result of its natural progression from ancient stations. The most probable hypothesis explaining its existence in Sousse roadstead would be its introduction linked to an anchoring of boat having brought alga fragments attached to its anchor from tha already colonized site. منذ ظهوره بالشمال الغربي للبحر الأبيض المتوسط 1984 لم ينقطع الطحلب الأخضر، أصيل المناطق الاستوائية ، كوليربا تاكسيفوليا عن النمو على طول السواحل الشمالية للمتوسط في منطقة ربوض السفن التجارية أمام ميناء سوسة (الجمهورية التونسية) بأعماق تبلغ 17 مترا. نعتقد أن الفرضية الأكثر احتمالا لتفسير تواجد هذا الطحلب الدخيل تتمثل في جلبه عن طريق مخاطيف البواخر التجارية القادمة من جنوب أوروبا والتي أرست في سواحل مدينة سوسة. Published

National audience

Problems caused by TBT and heavy metal-based antifouling paints on marine organisms led to the research for new non-toxic antifouling products. One of the most promising alternatives is the development of new coatings incorporating natural products from marine organisms. In the course of our investigation on the isolation of compounds with antifouling properties from Tunisian seaweeds, we studied the secondary metabolite content of the brown alga Dictyota fasciola. The dichloromethane and dichloromethane/methanol extracts showed noteworthy growth inhibition of marine bacteria and microalgae. A series of chromatographic separations of the crude extracts led to the isolation of six compounds in pure form: neodictyolactone, dictyol C, dictyol E, acetyldictyolal, sanadaol, and 18-hydroxy-2,7- dolabelladiene. However, the identity of the active compound(s) remains undetermined.

International audience

2nd Mediterranean Symposium on the Conservation of Coralligenous and other Calcareous Bio-Concretions, 29-30 October 2014, Portorož, Slovenia.-- 2 pages

Development of the national coralligenous monitoring protocol has been recently initiated in Croatia in the framework of the MedMPAnet project, with intention to primarily fulfill reporting and monitoring requirements of the EU Habitat Directive (92/43/EEC). However, basic information on coralligenous habitat along the Croatian coast is still lacking, which hinders a fixed definition of the monitoring methods and metrics to be used. Instead, we propose the basic methodological approach that will enable gathering the information needed and that will serve as a basis for reformulation of the adopted methods. The proposed monitoring protocol is based on the most recent (although scarce) knowledge on the monitoring approaches for this habitat, the compilation of available information for the coralligenous thriving along the Croatian coast as well as on the results of the fieldwork devoted to testing of the monitoring methods within the project. At each site, photosampling of minimum of three areas of 2.5 m2 (comprised of 10 contiguous photos of 50 x 50 cm quadrats to ensure species identification) will be combined with visual census along 10 m long horizontal transects, to gather information on habitat structure and function (species composition, habitat complexity, bioconcretion and bioerosion), as well as on the degree of impact of the main disturbances (mass mortalities, invasive species, sedimentation, mucilaginous aggregates, fishing gear). Down to 40 m depth this work will be carried out by SCUBA divers whereas the use of the Remote Operate Vehicles (ROVs) is envisaged at greater depths. The obtained information will both enhance knowledge on the coralligenous habitat along the Croatian coast and will provide an original data set to validate future indices of coralligenous health status, currently under development within other Mediterranean initiatives.

Proceedings accessible at : http://www.rac-spa.org/sites/default/files/symposium/proceedings_mscc_2019_final.pdf; International audience; Coralligenous habitats are bioconstructed, emblematic habitats of the Mediterranean Sea, which display a remarkably complex tridimensional structure and are considered as one of the most important biodiversity hotspots of the Mediterranean Sea. In order to assess the specific diversity of these habitats we sampled small surfaces (10 cm 2) of these habitats using a suction sampler in different environmental conditions on 19 sites in the Marseilles area (France). These samples were crushed and total DNA was extracted. A small portion of the COI gene was amplified using universal primers targeting metazoans. A total of 3029 Molecular Operationnal Taxonomic Units (mOTUs) were found among all samples. Most of the mOTUs belong to three taxonomic groups: Rhodophyta, Arthropoda and Annelida but many other phyla were detected. Environmental factors such as depth, slope and locality influence the community composition of coralligenous habitats. This first assessment of the specific diversity of these habitats using a metabarcoding approach confirms the status of biodiversity hotspot of these habitats and underlines the importance of abiotic variables to structure the community. Methodological developments can be used to design new monitoring protocols of these habitats.

International audience; Posidonia oceanicareefs along the French Mediterranean coast were inventoried and mapped using bibliographical data, analysis of aerial photos, images obtained using drone and 3D models. Sixteen previously unreported reefs and another 13 reefs that had been destroyed or disappeared were identified. In all, 75 Posidonia reef structures have were known to exist but today there are only 62 left.

Coralligenous outcrops are slow-dynamic habitats exhibiting high structural complexity. If these valuable habitats are degraded, relatively long time is required to recover their structure and full functionality. In order to reduce recovery times, restoration actions can focus on target habitat-forming species. Facilitation processes (i.e. positive species interactions), rarely considered to date, may be further explored to enhance the effectiveness of coralligenous restoration initiatives. Here we test if erect habitat- forming species, putatively modifying light penetration and/or water movement, can affect the survival and growth of co-occurring encrusting and massive ones. For that purpose, we designed an experiment using the red gorgonian Paramuricea clavata and bryozoans, important coralligenous structural animals, as model organisms. The experiment, replicated in Spain, Italy and Croatia, is based on the comparison between series of 0.25 m2 experimental plots. Experimental treatments include addition of bryozoan recruitment- enhancing devices (plastic grids) with and without gorgonian colonies and controls (empty and artefact ones) for a total of 4 replicates per treatment. The hypothesis is that the erect layer (15 P. clavata fragments up to 20 cm in maximal height per experimental plot) could facilitate the settlement of bryozoan colonies onto grids within the experimental plots and enhance their survival and growth. The experiment was initiated in May-July 2017 within the EU Horizon 2020 project MERCES (Marine Ecosystem Restoration in Changing European Seas, http://www.merces-project.eu/) and it is still ongoing. In this contribution we present and discuss our preliminary experimental findings.

Active restoration is considered a profitable strategy to return ecosystems to their predisturbance state, in a reasonable time frame. However, ecological restoration of marine ecosystems is still in its infancy if compared to the terrestrial context. A review of 498 studies published in the last 25 years was carried out within the MERCES H2020 EU project to understand the effects of marine restoration actions across coastal habitats at global scale. Here, an overview focused on the Mediterranean Sea was carried out to identify both contextual and methodological determinants of restoration success in the basin. Results show that restoration efforts across habitats are increasing, especially in seagrasses and saltmarshes, but never approached at ecosystem level. Targets, methods, response variables and standards are still very heterogeneous. Short project duration (one-two years), small restoration areas (< 1 ha), lack of controls and knowledge of baselines are still a limit for deriving generalities. Finally, restorations rarely consider future challenges linked to global change, thus impairing long- term success stories. Marine restoration is a promising approach to counteract habitat loss in coastal areas. However, restoration science needs more robust approaches leading to the development of best practices (e.g. protocols, monitoring of the effects, reasons for failure) to be applied at spatial and temporal scales so as to answer to present and future disturbance regimes.

Third Annual Meeting Marine Ecosystem Restoration in Changing European Seas (MERCES), 21-24 May 2019,Paris

The noble pen shell Pinna nobilis, an endemic Mediterranean bivalve is highly threatened by habitat loss or degradation due to intense coastal development, anchoring, trawling, illegal extraction and most recently, by a rapidly spreading disease. As a habitat-forming suspension-feeder this species contributes to water clarification and biodeposition and it enhances local biodiversity, especially in the seagrass meadows. To avoid smothering of this strictly protected species during construction of a new nautical centre in the Pula Harbour (North Adriatic Sea, Croatia), the environmental impact assessment prescribed transplantation of pen shells as a conservation measure. In the framework of EU Horizon 2020 project MERCES (Marine Ecosystem Restoration in Changing European Seas, http://www.merces- project.eu/), in coordination with the investor of the nautical centre and local volunteer divers we transplanted a total of 184 pen shells to the nearby Brijuni MPA, where their protection from adverse impacts of anchoring and illegal extraction couldbe ensured and monitoring of their survival could be performed. A high transplant survival confirmed that pen shell transplantation was an effective conservation/restoration method. This case represents the first official transplantation of a sessile marine species in Croatia as a measure prescribed by the environmental impact assessment and here we present our experience in connection with organisation and conduction of such action. Our aim is to facilitate and promote pen shell transplantation in the future as an appropriate and feasible conservation measure as well as to advise governing institutions on the issues that should be taken into account in the process.

The temperate coralligenous bioconcretions 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 recurrent 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 combined transplants from donor organisms using different techniques and recruitment-enhancing devices designed for habitat-forming species. Considering the life- history traits, population dynamics and population genetics of the selected species, restoration actions should be mainly based on transplants of small to medium size collected from donor specimens. Bearing in mind that survival of transplants is higher in species with slow growth rates such as those dwelling in the coralligenous than in more dynamic species, transplantation efforts in the coralligenous will require low initial effort but a long period will be required to fully recover habitat complexity, i.e. decades. We identified survival and growth of transplants and recruitment as the most suitable short-term indicators of the success of the restoration actions. Collaboration with volunteers (divers and diving operators) in several phases of field activities are being explored to cost- effective scaling up the restoration actions and to increase the sense of stewardship in a major users’ segment.

International audience; Coralligenous outcrops represent a "hotspot" of Mediterranean marine biodiversity. Algae and sessile invertebrate taxa (mainly sponges, cnidarians, bryozoans and tunicates) structure the associated benthic assemblages and constitute remarkable seascapes. Nevertheless, this fragile habitat is submitted to a wide array of human impacts such as sewage outfalls, eutrophication, physical impacts linked to fishing and diving activities, as well as global warming effects. The current European legislative context (EU WFD, EU Habitat Directive, EU MSFD) imposes to reach or maintain a good environmental status for marine ecosystems. In this context, the MPA stakeholders need to have robust and accessible tools allowing the evaluation of the conservation state of the habitats. Concerning coralligenous bottoms, we propose a new method based on an integrated approach taking into account (i) the ratio between sensitive and tolerant species according to human impacts, (ii) the richness of macrotaxonomic descriptors assessed from direct observation (in situ or from images) and (iii) their structural complexity (basal, intermediate and upper layers present in coralligenous bottoms). These three metrics are combined into a global index called INDEX-COR. Datasets were acquired along the French coasts. In each site, 2 transects 15m long were installed on the bottom. Along each transect, 15 photo quadrats (40 cm x 60 cm) and 1 video were recorded and notes were taken by a SCUBA diver-Observer. This method was applied between 15 and 50 meters depth and can be also performed by a ROV (Remotely Operating Vehicule) or an AUV (Autonomous Underwater Vehicle). INDEX-COR is intended to be applied to other Mediterranean areas using metrics and species lists adapted to the different regional contexts.

International audience; A preliminary study of coralligenous benthic assemblages was performed in 2013 at 20 sites in Turkey, Greece and France within the framework of the EU-funded project CIGESMED. At each area the most conspicuous species were recorded using in situ observations and photoquadrats. The survey revealed a total of 267 species belonging to 11 systematic groups. Within the sampled sites, algae ranked first in terms of species richness (83 species), followed by Porifera (55 species), Cnidaria (32 species), Bryozoa (22 species) and Echinodermata (21 species). A total of 172 species were encountered in France, 107 species in Turkey and 93 species in Greece. Six alien species, Caulerpa cylindracea, Stypopodium schimperi, Acrothamnion preissii, Womersleyella setacea, Amphistegina lobifera and Synaptula reciprocans, were found at sampling sites. Taking into account the preliminary character of the performed surveys, the biodiversity reported herein is presumably underestimated. Species richness is expected to increase following the upcoming, more exhaustive CIGESMED surveys. The final species lists will later be critically evaluated to meet the needs for developing new biotic indices and also for applying already developed ones (e.g. Index-Cor) in order to be used by scientists, managers and stake holders for the effective monitoring and management of coralligenous communities.

International audience; The so-called coralligenous makes Mediterranean marine habitats that are of the most important in terms of complexity and biodiversity. Coralligenous is formed by the development of several types of communities where bio-constructor, bio-erodor engeneer and " habitat " species interact to build complex structures. The European program CIGESMED studies the Good Environmental Status (G.E.S.) of these habitats. Several protocols are implemented, in particular the cartography of abiotic context, and species observation by means of photo-quadrats. The cartography inventories the profiles types of the coralligenous sites with as robust as possible categories: depth, orientation, slope, roughness, and main coralligenous stands. The objective is to establish a link between the species occurrence features, and the profiles features in order to understand the " natural " spatial variability of coralligenous habitats.

International audience; The European program CIGESMED addresses the Good Environmental Status of the coralligenous habitats. Its implementation on the field is firstly attempted by 4 protocols to be applied in France, Greece and Turkey. They have been tested in Marseille's region, since early 2014. These protocols are the following: (i) cartography of chosen coralligenous sites, (ii) spatial variability analysis by means of photo-quadrats and image processing, (iii) population genetics study of two common biobuilding species that may be cryptic (the bryozoan Myriapora truncata, and the rhodophyta Lithophyllum cabiochiae), and (iv) metagenomic approach of benthic species. The ultimate aim of these protocols is to link the results from the population genetics analysis and the spatial variability analysis to the sites' features thanks to the cartography. First results suggest that different clades exist for both complex of the previous species. Cartography forshadows models of repartition for species assemblages; they will then be compared between regions in the second part of the project.

Along Mediterranean coasts, canopy-forming seaweeds used to form diverse, productive and valuable “forest” habitats, but in the past decades conspicuous declines, sometimes to local extinction, have been reported in many regions. Canopies are retracting particularly close to urban areas, and are replaced by turf-forming and ephemeral algae or barrens. The persisting forests are under continued threat, and current protection measures are insufficient. We provide evidence that declines of canopy algae are dramatically extensive, and are driven by multiple local (nutrient enrichment and high sediment loads, fishing, heavy metal pollution) and global stressors (increasing temperature, high wave exposure). We also show that the combined management of local stressors (such as nutrients and sediments) would increase significantly the resilience of canopy algae to future climatic stressors, preventing their further deterioration. Finally, we discuss restoration prospects in areas where these systems have been lost. We conclude identifying the main needs to understand, guide and motivate effective conservation actions in these valuable ecosystems.

Regular monitoring of Posidonia oceanica (L.) (Posidoniaceae) is required under EC directives, and its purpose is to inform management agencies when and where actions are necessary to protect and restore ecological health and water quality. The Habitats Directive requires each EU member nation to report specifically on temporal trend in areal extent of Posidonia habitat. The success of the HD hinges on the power of the monitoring protocol to reveal a significant negative trend, wherever that trend occurs in nature. Statistical power is determined by the size of the sampling error of the protocol, which includes measurement uncertainty and natural spatial variation in the descriptor. We review several descriptors of Posidonia status, and consider published estimates of their typical sampling errors, to compare their ability to demonstrate a 10% temporal trend. We find that the protocols with potentially high statistical power are fixed-plot methods such as SeagrassNet and balisage, high resolution aerial photography, and remote underwater videography. The lowest statistical power is found for random plot protocols using descriptors from the interior meadow such as shoot density measured by SCUBA in 40 x 40 cm quadrats. The main advantage of videography over direct SCUBA methods is the ability to sample 20-30 times the area sampled by the equivalent SCUBA labour, but with none of the fatigue or discomfort. The main advantage of videography over aerial photography or acoustic imaging is its high resolution and near-perfect habitat classification accuracy for live seagrass, dead matte, and non-seagrass benthic habitats. We recommend remote underwater videography as a low-cost method of uncovering trends in Posidonia cover with high statistical power.

2nd Mediterranean Symposium on the Conservation of Coralligenous and other Calcareous Bio-Concretions, 29-30 October 2014, Portorož, Slovenia.-- 6 pages, 2 figures, 1 table

Several episodes of mass mortalities, affecting populations of corals and other sessile invertebrates, have been recorded over the past 20 years in the eastern part of the Adriatic Sea. The coralligenous community, one of the most diverse in the Mediterranean Sea where suspension feeders are dominant, has been also strongly affected by these events. Current hypotheses about the causes of mass mortality events mostly focus on their relationship with the occurrence of distinctive climatic anomalies during the late summer and early fall, when the thermocline shifted to deeper areas, to more than 40 m depth. Their occurrence and characteristics differed among regions and years and were usually related to the local hydrological conditions. The species affected were mostly long-lived sessile epibenthic invertebrates, such as sponges, anthozoans, bivalves, bryozoans and ascidians. During the two large mass mortality events in 2003 and 2012 in the Adriatic Sea, sea temperatures reached up to 6°C above the average with prolonged water column stability during late summer, and affected approximately 30 marine species down to 40 m depth. The main goal of this study is to provide a comprehensive report on the impact of the mass mortality events by providing data on the species affected, the intensity of the impact, the depth range, and the timing of the event for three study areas in the eastern Adriatic Sea. According to the data obtained, the sites surveyed in the northern part of the Adriatic Sea were the least affected, while the sites in the central and southern Adriatic displayed the highest impact.

2nd Mediterranean Symposium on the Conservation of Coralligenous and other Calcareous Bio-Concretions, 29-30 October 2014, Portorož, Slovenia.-- 6 pages, 2 figures, 1 table

Multi-Beam Echo-Sound data, Remotely Operated Vehicle video-images and grab samples were collected, within the framework of the research project funded by the Italian Ministry in charge of fisheries management - MiPAAF, in order to improve the knowledge on the Italian Rhodolith Beds Habitat (RBs). The aim of this paper is to assess the composition of RBs and of their associate macroalgal epiphytes in the North Western Mediterranean Sea. The study sites are located in the Tuscan Archipelago (Tyrrhenian Sea), where RBs occur between 50 and 70 meter depth. The most frequent calcareous taxa were: Phymatolithon calcareum, Lithothamnion minervae, Lithothamnion philippii, Lithophyllum racemus and Titanoderma pustulatum. In all the sampled sites both the taxa of Annex V of the Habitat Directive, P. calcareum and/or Lithothamnion corallioides, were collected.

The management of the red coral, Corallium rubrum (L.), is an international issue still lacking of an effective solution in the Mediterranean Sea. The main goal of this research was the evaluation of the ROV efficiency as a monitoring non-destructive tool in studies concerning the conservation status of the deep red coral populations (living under 50 m depth). Both Ligurian Sea and Tuscan Archipelago are considered among the most important Italian historical sites of the red coral professional harvesting. Fishing effort in these areas is now decreased (in Liguria is virtually ceased) due to the drastic reduction of colonies of commercial size and thanks to conservation laws. Today, the protection of this natural resource has been directed mainly to coastal, shallow-water populations (living between 20 and 40 m depth), while the deeper banks, the main target of professional harvesting by technical scuba divers, still need dedicated management plans. ROV explorations allowed the identification of several deep red coral banks: in the Ligurian Sea, 6 out of 12 explored sites (50%) and in the Tuscan Archipelago, 7 out of 13 explored sites (50%). The banks may be considered almost "pristine" only around Montecristo Island. In the Ligurian Sea, the only deep population in a good conservation status is that of the Maledetti Shoal, off the Bergeggi Island MPA.

Mortality events of the corals Cladocora caespitosa (Linnaeus, 1767), Madracis pharensis (Heller, 1868) and Balanophyllia europaea (Risso, 1826) were recorded along the eastern coast of Adriatic Sea. Coral mortality resulted from polyp bleaching (massive zooxanthellae loss) and polyp tissue necrosis, leaving the calyx rim deprived of tissue coverage. The highest mortality rates were registered after the exceptionally hot summer of 2011, when about 30% of C. caespitosa and M. pharensis colonies were affected and more than 40% of the B. europaea species died, all caused by bleaching events. Similar events were found during late summers of 2003, 2007, 2008, 2009, 2011 and 2012. In most cases bleaching has been attributed to elevated temperature. Taking into account the global warming context in the Mediterranean Sea, monitoring programs of physical-chemical parameters and vulnerable coral populations should be rapidly set up.

The distribution of Eunicella cavolini (Anthozoa) was mapped based on scientific data and observers’ information, in order to depict its geographical range across the Mediterranean. Moreover, an overview of scientific literature was realized to assess the current state of knowledge regarding its populations. Results show that E. cavolini displays an extensive distribution, from the Alboran to the Sea of Marmara, but is more common at the Italian, French, E Adriatic and N Aegean coasts. Populations were mainly recorded at depths of

Remote aerial or satellite images of the Croatian Adriatic have revealed several locations of circular damage to Posidonia meadows extending back in time over a decade. In some locations these circles exist as a regular linear series on remote island shores, and at other locations they appear haphazardly positioned and sometimes overlapping. Our aims are to determine possible causes of this damage, obtain estimates of the time of damage, and to monitor the rate of Posidonia recovery. The damage circles are likely caused by submarine explosions, for example from blast fishing or military shelling. We expect that more than one type of human activity will be required to explain all the Posidonia damage circles in Croatia.

Mapping of Mediterranean rhodolith beds (RBs) should be focussed on areas of the seafloor with >10% cover of live calcareous red algae for a minimum surface of 500m2, on 1:10000 scale. More detailed scales (at least 1:1000) should be used for monitoring selected RBs, in order to detect significant changes through time. Beside the location and areal extent, the description of a RB that could be provided by non-specialists should include the occurrence of macroscopic sedimentary structures of the seafloor, thickness of live cover, mean percentage cover of live thalli, and dominant morphologies of rhodoliths (unattached branches, pralines or boxwork rhodoliths). For the purpose of ecological status assessment and the evaluation of human-induced impacts, the protocol requires the support of specialists to add details on the assemblage composition

Ecological differences along the Adriatic Sea (climatic differences along the NW-SE axis, higher eutrophication in the North Adriatic, and higher natural eutrophication in the area between the islands or inside deep indented bays) influence Posidonia oceanica distribution and the appearance of its meadows. As the baselines of descriptors for Posidonia meadows for a particular area in the Croatian Adriatic have not yet been established we argue that non-critical and untested use of baselines of descriptors and classification methods that exist for Posidonia meadows in the NW Mediterranean could lead to erroneous conclusions and an incorrect assessment of meadow conservation status.

Global change is one of the major concerns for the conservation of the rich biodiversity of coralligenous assemblages. In the Mediterranean Sea, there is a strong likelihood of increasing frequencies of mass mortality events linked to global warming and the spread of invasive species. Gorgonian forests, one of the most emblematic facies of coralligenous outcrops, are especially vulnerable to global change. The presentation will focus on the study of the responses of gorgonians, mainly the red gorgonian Paramuricea clavata, to warming and exotic algae invasions from observational and experimental approaches in NW Mediterranean Sea. Long-term monitoring of recurrent warming- induced mortalities in marine protected areas such as Cabrera Archipelago and Columbretes Islands showed that warming may act as an important driver for long-term shifts in the bathymetrical distribution of gorgonian forests. Aquaria experiments and field surveys indicate that thermal stress may also have important sublethal effects on the reproduction and the viability of early life stages of gorgonians. Additionally, manipulative experiments demonstrated that invasive algae, such as Caulerpa cylindracea and Womersleyella setacea, have the capacity to reduce gorgonian recruitment and juvenile survival. The final aim of the presentation is to discuss the future consequences of global change on the persistence and recovery of gorgonian forests, in particular, and of coralligenous assemblages in general.

Recent studies have investigated spatial and temporal variability of coralligenous assemblages on coastal rocky cliffs, while structure and variability of platform banks have been rarely investigated. In the northern Adriatic continental shelf, coralligenous biogenic reefs are scattered on sandy and muddy bottoms, and may be separated by a few tens of meters to tens of kilometres. Their benthic assemblages were investigated by photographic sampling in two main areas about 100 km away: off Chioggia-Venice and Grado-Trieste. Within each area six outcrops, 1-2 km away, were sampled. Assemblages on reefs closer to the coast were dominated by algal turfs and boring sponges, while offshore they were generally characterised by the richest and most diverse communities. Contributions to the total species richness increased with the investigated spatial scale up to areas, while variation in species diversity monotonically decreased by increasing distance. Dominant species, including the main reef builders (i.e. encrusting calcified Rhodophyta), spatially changed following a geographical pattern. Among others, coralline algae (e.g. Lithophyllum incrustans), sponges (e.g. Chondrosia reniformis) and colonial ascidians (e.g. Polycitor adriaticus) were the main species responsible for the observed spatial differences, in terms of species replacement (β diversity).

The genus Hydrolithon, together with Porolithon, is one of the most discussed groups of Corallinaceae, as well as one of the most poorly known. Morphological observations led to different interpretations mainly due to the lack of type material. Recently molecular surveys on the phylogeny of Corallinales supported the hypothesis of considering Hydrolithon and Porolithon as two distinct genera, but, up to now, several taxonomic questions remain partially unanswered. In this study we report the discovery of a new non-geniculate encrusting species found along the coast of Vis Island, Croatia, Adriatic Sea. Morphological observations suggest that the specimens could belong to the Hydrolithon/Porolithon complex. Molecular analyses based on the nuclear 18S rDNA (SSU) and the plastidial psbA markers were carried out. This finding represents the first report of this new coralline alga in the Mediterranean Sea.

International audience; Les herbiers à Posidonia oceanica présentent plusieurs types morpho-structuraux généralement conditionnés par les conditions de milieu (profondeur, hydrodynamisme, substrat, pente, turbidité, sédimentation). Du fait de leur rareté, deux structures particulières, les récifs barrière et les herbiers tigrés, sont considérées depuis une vingtaine d'années comme des paysages marins menacés. Initialement décrits dans le golfe de Gabés, à proximité des îles Kerkennah, les herbiers tigrés se présentent sous forme " de rubans assez étroits qui se développent entre 0.5 et 3 m de profondeur sur matte ". La mise en place de nouveaux programmes d'études sur les herbiers à Posidonia oceanica et l'optimisation de l'imagerie satellitaire (accessibilité, résolution, coût) ont permis d'acquérir de nombreuses données dans plusieurs secteurs de Méditerranée et d'actualiser notre connaissance de ces structures. Il apparaît ainsi que les herbiers tigrés sont mieux représentés au niveau de la rive Sud du bassin (Golfe de Gabès, littoral de Zarzis en Tunisie, lagune de Farwa et littoral à l'Est de Tripoli en Libye) et dans des îles méditerranéennes (Marsala-Stagnone en Sicile et Porto-Vecchio en Corse). D'autre part la présence d'herbiers tigrés sur roche a été observée pour la première fois en Libye sur un platier rocheux à l'Est de Tripoli. Compte tenu de leur rareté et des pressions qu'elles subissent, il apparaît urgent de classer ces structures comme " monuments naturels " et mettre en œuvre une politique efficace pour assurer leur conservation

Although seagrass meadows are known for their value as animal habitat, little information exists on the relative habitat value of individual species. We investigated populations of cooccurring seagrasses Zostera marina, Z. noltii, and Cymodocea nodosa and their associated macro-fauna within their physical context in seven distinct embayments in the central Croatian Adriatic Sea. Total seagrass cover varied significantly among embayments, was negatively affected by slope of the sea bottom, and positively affected by marina developments. Variation in coverage of individual seagrass species within and between bays significantly correlated with depth, wave exposure, and salinity. At three meters depth, faunal abundance was higher in monocultures of C. nodosa (four times) or Z. noltii (seven times) than in beds of Z. marina (pure or invading Z. noltii). Likewise, the effective number of taxa (diversity) was higher in Z. noltii and C. nodosa than in Z. marina. Several taxa were exclusively found either in C. nodosa or Z. noltii meadows. Our results are consistent with the hypothesis that physical processes control seagrass cover and distribution, and that this species-specific cover and distribution has significant and predictable effects on the associated animal assemblage.

The endemic Mediterranean marine phanerogam Posidonia oceanica (L.) Delile forms dense beds characteristic of the photic infralittoral zone. As elsewhere in the Mediterranean, they are considered to be the most important shallow benthic habitat in the Adriatic Sea. This complex habitat/biocoenosis, with high primary production and high biodiversity, is important for the oxygenation of the seawater and stabilization of the sediment. However, in the Croatian part of the Adriatic the biocoenosis is poorly known. The aim of this research was to compare biometry and leaf lepidochronology of seven Posidonia meadows in the Middle and South Adriatic studied from 2002 to 2006 (on Islands Dugi otok, Krapanj, Vis and in the Lastovo Archipelago). In well-developed meadows, 20-50 Posidonia shoots per meadow were taken along the depth gradient. The upper and the lower bathymetric extension of the meadows and the number of shoots along the depth/light gradient (in 10 quadrats 40 x 40 cm per each depth) were determined in situ. Variables measured included shoot density, leaf area index, biomass, and estimated annual primary production. Meadow density and the effect of depth on estimated primary production were compared among the researched meadows as well as with the published data for Posidonia beds in the Mediterranean. Generally, meadows under the influence of open Adriatic clear waters showed the highest primary production: in Lojisce cove (Dugi otok) and Rukavac cove (Vis). Estimated primary production in our studied Posidonia meadows was similar to the estimated primary production of other meadows in the Mediterranean Sea. However, meadows in enclosed bays (Cuska Dumboka, Sascica) showed remarkably lower primary production, probably due to natural eutrophication and lower water clarity.