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This task report has been elaborated within the framework of the "Improving coverage and management effectiveness of marine and coastal protected areas - Phase 2" Project (2017-2021). Project partners: UNDP Albania, Agenzia Italiana per la Cooperazione allo Sviluppo (AICS) and National Agency of Protected Areas (NAPA) / Agjencia Kombëtare e Zonave të Mbrojtura, në Shqipëri (AKZM).

Healthy coralligenous habitats may host dense populations of gorgonians, like Paramuricea clavata and Eunicella cavolini that build marine animal forests. According to recent studies, these forests appeared able to increase the resilience of coralligenous habitats and to enhance the structural complexity and bioconstruction processes. They are also able to increase species diversity and limit the invasion of alien species. The major limitation in the conservation of these forests is the lack of knowledge on their actual distribution and the extents of their ecological roles. Nowadays, by combining information from scientific literature, citizen science projects and the World Wide Web is possible to fill part of these gaps and draw a more comprehensive picture for the Mediterranean Sea. This knowledge represents the baseline to address effective conservation measures on gorgonian forests and coralligenous accretions.

This task report has been elaborated within the framework of the "Improving coverage and management effectiveness of marine and coastal protected areas - Phase 2" Project (2017-2021). Project partners: UNDP Albania, Agenzia Italiana per la Cooperazione allo Sviluppo (AICS) and National Agency of Protected Areas (NAPA) / Agjencia Komb��tare e Zonave t�� Mbrojtura, n�� Shqip��ri (AKZM).

Relazione conclusiva del progetto di caratterizzazione dell’area di foce del Torrente Bevano e individuazione delle strategie di conservazione e valorizzazione delle aree di nursery per specie protette e d’interesse commerciale, realizzato dal Centro Interdipartimentale di Ricerca per le Scienze Ambientali (CIRSA) ALMA MATER STUDIORUM - Università di Bologna nell’ambito della Azione 2.A.a) “Habitat marini e lagunari – Studi e ricerche” del FEAMP 2014/2020, Regione Emilia-Romagna.

The coralligenous reefs are among the richest and threatened habitats in the Mediterranean Sea. They are the result of the interplay between the building activities and physical and biological eroding processes. In the Mediterranean Sea, dense populations of Paramuricea clavata shape animal forests characterising the seascapes of coralligenous habitats. After the general introduction, the abundance and composition of epibenthic assemblages inside and outside P. clavata forests were investigated across the Mediterranean Sea. According to this study, the gorgonian understoreys may enhance bioconstruction processes and increase resistance and resilience of the benthic assemblages in the coralligenous habitats. Mediterranean gorgonian are threatened by anthropogenic disturbances and mass mortality events. These events have often been linked to anomalies in the temperature profiles. A temperature-based surveillance tool was proposed by utilising oceanographic analysis and forecast models. Such a tool would allow for the timely study of mass mortality phenomena and the implementation of prompt restoration initiatives. The North Adriatic Sea hosts a large number of biogenic reefs. Computed Tomography has been used to analyse 3 and 12 years bioconstruction and bioerosion processes occurring in experimental tiles. The mean erosion rate increased with time, while the mean construction rate appeared to decrease. Experimental data combined with new technologies allow assessing the bioerosion and bioconstruction processes, which is a fundamental step towards the conservation of biogenic reefs. The need to assess the environmental quality status of coralligenous habitats and to fulfil the goals of the MSFD, suggest the opportunity to develop indices based on Citizen Science project that may support decision-makers in planning conservation strategies. The Reef Check Mediterranean Species Sensitivity (MedSens) index is proposed. MedSens index provides the mean sensitivity of the surveyed assemblages; helping to assess the environmental quality status and to identify the most likely disturbs acting in the study area.

International audience

Il progetto di Citizen Science, Together for Tavolara, articolato in quattro azioni di conservazione e monitoraggio condotte con il supporto degli studenti e dei cittadini coinvolti, rappresenta un elemento di continuità con le attività quotidiane di tutela messe in campo dal Consorzio di Gestione dell’AMP di Tavolara Punta Coda Cavallo, dalla sua istituzione nel 2004. Attraverso questo progetto sono state diffuse informazioni e conoscenze sulle specie aliene invasive e sulle problematiche da esse generate. Questo fenomeno è strettamente correlato con le principali criticità che definiscono il nostro tempo: i cambiamenti climatici, la riduzione della biodiversità e l’impoverimento degli ambienti, contribuiscono a favorire la diffusione delle specie aliene e ne amplificano gli impatti. Il coinvolgimento attivo delle comunità e la partecipazione diretta a semplici protocolli di monitoraggio consentono di promuovere consapevolezza e senso di appartenenza, rafforzando la volontà di contrastare con il proprio impegno diretto le questioni ambientali emergenti. È questo il valore aggiunto dei percorsi di Scienza del cittadino. Questa pubblicazione è uno strumento operativo di lavoro e di divulgazione nato per questo progetto, ma speriamo sia utile anche in altre esperienze ed attività, anche di singoli cittadini che volessero approfondire queste tematiche.

The proposed Mediterranean Reef Check Species sensitivity (MRC-Ss) index, based on data provided by volunteer scuba divers, may represent a proxy of the mean sensitivity of the assemblages toward the natural and anthropic disturb agents indicated by the European Marine Strategy Framework Directive. Its application may represent the occasion to raise public awareness and enhance the collaboration between coastal management authorities (e.g., MPA managers) and dive centres, through a participatory approach.

1. The aim of the present study was to propose a biotic index (North Adriatic Mesophotic BiogEnic Reefs, NAMBER) suitable for assessing the ecological quality of the mesophotic biogenic reefs of the northern Adriatic continental shelf based on photographic sampling. 2. At each of the 20 study sites, the degree of bioconstruction (expressed as percentage cover of crustose coralline algae), the α-diversity (expressed as the mean number of taxa), and the degree of sensitivity to human disturbance and climate change (based on literature data and expert judgement) of the benthic assemblages were selected as descriptors and combined in the NAMBER index, using the best values that the three metrics can currently achieve in the studied region as a reference. 3. The study highlighted that there was large spatial heterogeneity among reefs and high variability in the ecological quality values obtained by NAMBER, ranging from bad to high. The index indicates that reefs lying furthest from the coast, under substantially lower anthropogenic pressure, have a generally higher status of environmental quality. However, a clear geographical pattern did not emerge, as reefs close together often had different ecological qualities. 4. The NAMBER index, which combines three ecological descriptors, in accordance with the requirements of the European Marine Strategy Framework Directive, represents a specific adaptation to the northern Adriatic Sea of a multimetric index previously developed for the north-western Mediterranean Sea, capitalizing on previous knowledge and research efforts. 5. This multimetric biotic index provides an effective standardized tool for monitoring programmes and environmental impact assessments in the northern Adriatic mesophotic biogenic reefs and lays the foundation for ecosystem-based management and conservation in this basin.

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.

Artisanal and small-scale gold mines (ASGMs) have been accompanied by widespread usage of mercury amalgamation to extract gold from ores, putting Indonesia among the top three global emitters of this pollutant and posing potential risks to the marine ecosystem and human health. Although the use of mercury has been largely eliminated following the signature of the Minamata Convention on Mercury, the practice of mercury amalgamation in ASGM has persisted in several regions, including the North Sulawesi. This study assesses how on the contamination of mercury and other trace elements coming from both industrial mines and ASGMs affects marine sediments and their bioaccumulation in two tissues (body wall and guts) of the edible holothurian Holothuria (Halodeima) atra, by comparing samples collected downstream of four mining areas to four control sites in the North Sulawesi province, Indonesia. In sediments, mean concentrations of arsenic, gold, cobalt, chromium, copper, mercury, nickel, lead, antimony, and zinc were significantly higher at sites receiving mine discharges than at control sites. Downstream to gold mines, compared to control sites, significant higher concentrations of As, Au, Cr, Hg, and Ni in holothurians body walls and of As, Au, Co, Cr, Cu, Hg, Pb, Sb, Sn, and Zn in holothurians guts were found. In general, higher contaminations in sediments and tissues were found at the site near the oldest artisanal mine. Trace element levels in H. atra specimens in North Sulawesi were generally higher than those reported in other regions. In the study area, these holothurians significantly bioaccumulate Hg, As, Zn, Cd, Cu, Sn, and biota-sediment accumulation factors were higher in guts than in body walls. From an environmental and human health perspective, Hg is resulted the most concerning element in surface sediment and H. atra specimens. Based on this evidence, further studies are urgently needed to understand better the effect of mercury and other potentially toxic trace elements in marine ecosystems and food webs in mining areas both in North Sulawesi and in many still poorly investigated southeast Pacific areas.

The northern Adriatic continental shelf hosts several coralligenous reefs rising from the sedimentary bottom and characterized by three main benthic assemblages, respectively, dominated by algal turfs, encrusting calcareous rhodophyte (ECRs) or erect sponges. Bioconstruction and bioerosion processes have been investigated using recruitment travertine limestone tiles deployed in a random site for each main benthic assemblages off Chioggia, 6.1–14.4 km offshore and 20.2–25.4 m depth. Tiles were retrieved after 3 and 12 years and analyzed by X-ray computed tomography (CT), allowing for non-destructively identifying and quantifying deposited and eroded limestone. The main builders were ECRs, serpulids, bryozoans, barnacles, and the bivalves Anomia ephippium, while the most effective borers were sponges from the genus Cliona and the bivalve Rocellaria dubia. The deposition of limestone after 12 years was greater at the site MR08 dominated by ECRs (12.52 ± 2.22 kg m–2), intermediate at the site P213 dominated by erect sponges (4.20 ± 1.24 kg m–2), and lower in the site P204 dominated by algal turfs (2.20 ± 0.72 kg m–2). At MR08, the deposition rate did not vary much over time (from 1.295 ± 0.270 to 1.080 ± 0.198 kg m–2 a–1), while in the other two sites, it significantly slowed down after the first survey period: from 0.952 ± 0.199 to 0.350 ± 0.103 kg m–2 a–1 at P213, and from 1.470 ± 0.462 to 0.203 ± 0.058 kg m–2 a–1 at P204. The amount of eroded limestone increased with the exposure time, with no significant differences among sites, from 1.13 ± 0.29 to 10.39 ± 1.14 kg m–2 on average at 3 and 12 years, respectively. The bioerosion rate also increased with the exposure time and was slightly higher at MR08 (from 0.682 ± 0.208 to 1.105 ± 0.088 kg m–2 a–1), mostly eroded by Cliona rhodensis in addition to C. viridis, compared to P204 (from 0.267 ± 0.078 to 0.676 ± 0.172 kg m–2 a–1) and P213 (from 0.179 ± 0.065 to 0.816 ± 0.171 kg m–2 a–1). Overall, bioconstruction has overcome the bioerosion processes in 3 years. In 12 years, the estimated net balance was essentially nil at all sites. Combining field experiment and CT analysis, this study provides the first quantification of the bioerosion and bioconstruction processes in the northern Adriatic coralligenous reefs, a fundamental step toward their conservation.

Citizen science (CS) projects may provide community-based ecosystem monitoring, expanding our ability to collect data across space and time. However, the data from CS are often not effectively integrated into institutional monitoring programs and decision-making processes, especially in marine conservation. This limitation is partially due to difficulties in accessing the data and the lack of tools and indices for proper management at intended spatial and temporal scales. MedSens is a biotic index specifically developed to provide information on the environmental status of subtidal rocky coastal habitats, filling a gap between marine CS and coastal management in the Mediterranean Sea. The MedSens index is based on 25 selected species, incorporating their sensitivities to the pressures indicated by the European Union’s Marine Strategy Framework Directive (MSFD) and open data on their distributions and abundances, collected by trained volunteers (scuba divers, free divers and snorkelers) using the Reef Check Mediterranean Underwater Coastal Environment Monitoring (RCMed U-CEM) protocol. The species sensitivities were assessed relative to their resistance and resilience against physical, chemical, and biological pressures, according to benchmark levels and a literature review. The MedSens index was calibrated on a dataset of 33,021 observations from 569 volunteers (2001–2019), along six countries’ coasts. A free and user-friendly QGIS plugin allows easy index calculation for areas and time frames of interest. The MedSens index was applied to Mediterranean marine protected areas (MPAs) and the management and monitoring zones within Italian MPAs. In the studied cases, the MedSens index responds well to the local pressures documented by previous investigations. MedSens converts the data collected by trained volunteers into an effective monitoring tool for the Mediterranean subtidal rocky coastal habitats. MedSens can help conservationists and decision-makers identify the main pressures acting in these habitats, as required by the MSFD, supporting them in the implementation of appropriate marine biodiversity conservation measures and better communicate the results of their actions. By directly involving stakeholders, this approach increases public awareness and the acceptability of management decisions, enabling more participatory conservation tactics.

9 pages, 2 figures.-- Data Availability Statement: All datasets generated for this study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s, Marine animal forests are benthic communities dominated by sessile suspension feeders (such as sponges, corals, and bivalves) able to generate three-dimensional (3D) frameworks with high structural complexity. The biodiversity and functioning of marine animal forests are strictly related to their 3D complexity. The present paper aims at providing new perspectives in underwater optical surveys. Starting from the current gaps in data collection and analysis that critically limit the study and conservation of marine animal forests, we discuss the main technological and methodological needs for the investigation of their 3D structural complexity at different spatial and temporal scales. Despite recent technological advances, it seems that several issues in data acquisition and processing need to be solved, to properly map the different benthic habitats in which marine animal forests are present, their health status and to measure structural complexity. Proper precision and accuracy should be chosen and assured in relation to the biological and ecological processes investigated. Besides, standardized methods and protocols are strictly necessary to meet the FAIR (findability, accessibility, interoperability, and reusability) data principles for the stewardship of habitat mapping and biodiversity, biomass, and growth data, This perspective manuscript is the result of the 3DSeaFor online workshop funded by EUROMARINE Call 2019 Foresight Workshops. This work was partially supported by an Italian Research Projects of National Interest (PRIN), funded by the Italian Ministry of University and Research: “Reef ReseArcH – Resistance and resilience of Adriatic mesophotic biogenic habitats to human and climate change threats” (Call 205; Prot. 2015J922E; 2017-2020) and by the TAO (Tecnologie per il monitorAggio cOstiero) project in the frame of the program POR-FESR (European Regional Development Fund, ERDF) 2014-2020 of the Emilia-Romagna Region. This work was partially supported by the U.S. National Science Foundation under Grant No. OCE 16-37396 (and earlier awards) as well as a generous gift from the Gordon and Betty Moore Foundation, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Marine biodiversity underpins ecosystem health and societal well-being. Preservation of biodiversity hotspots is a global challenge. Molecular tools, like DNA barcoding and metabarcoding, hold great potential for biodiversity monitoring, possibly outperforming more traditional taxonomic methods. However, metabarcoding-based biodiversity assessments are limited by the availability of sequences in barcoding reference databases; a lack thereof results in high percentages of unassigned sequences. In this study we (i) present the current status of known vs. barcoded marine species at a global scale based on online taxonomic and genetic databases; and (ii) compare the current status with data from ten years ago. Then we analyzed occurrence data of marine animal species from five Large Marine Ecosystems (LMEs) classified as biodiversity hotspots, to identify any consistent disparities in COI barcoding coverage between geographic regions and at phylum level. Barcoding coverage varied among LMEs (from 36.8% to 62.4% COI-barcoded species) and phyla (from 4.8% to 74.7% COI-barcoded species), with Porifera, Bryozoa and Platyhelminthes being highly underrepresented, compared to Chordata, Arthropoda and Mollusca. We demonstrate that although barcoded marine species increased from 9.5% to 14.2% since the last assessment in 2011, about 15,000 (corresponding to 7.8% increase) new species were described from 2011 to 2021. The next ten years will thus be crucial to enroll concrete collaborative measures and long term initiatives (e.g., Horizon 2030, Ocean Decade) to populate barcoding libraries for the marine realm., the Department of Biological, Geological and Environmental Sciences (BiGeA) of the University of Bologna (UniBo). The CoMBoMed initiative was supported by the European Marine Research Network (EUROMARINE Network), the Inter-Departmental Research Centre for Environmental Sciences (CIRSA – UniBo), the Cultural Heritage Department (DBC - UniBo, https://beniculturali.unibo.it/it), the Fondazione Flaminia and the ERANet Mar-Tera Project SEAMoBB (Solutions for sEmi-Automated Monitoring of Benthic Biodiversity).

Since 2001, trained snorkelers, freedivers, and scuba diver volunteers (collectively called EcoDivers) have been recording data on the distribution, abundance, and bathymetric range of 43 selected key marine species along the Mediterranean Sea coasts using the Reef Check Mediterranean Underwater Coastal Environment Monitoring (RCMed U-CEM) protocol. The taxa, including algae, invertebrates, and fishes, were selected by a combination of criteria, including ease of identification and being a key indicator of shifts in the Mediterranean subtidal habitats due to local pressures and climate change. The presence and abundance of gas bubbles leaching from the seabed are also recorded. The dataset collected using the RCMed U-CEM protocol is openly accessible across different platforms and allows for various uses. It has proven to be useful for several purposes, such as monitoring the ecological status of Mediterranean coastal environments, assessing the effects of human impacts and management interventions, as well as complementing scientific papers on species distribution and abundance, distribution modeling, and historical series. Also, volunteers’ commitment promotes marine stewardship and environmental awareness in marine conservation. Here, we describe the RCMed U-CEM protocol, from training volunteers to recording, delivery, and sharing data, including the quality assurance and control (QA/QC) procedures.

Since 2001, trained snorkelers, freedivers, and scuba diver volunteers (collectively called EcoDivers) have been recording data on the distribution, abundance, and bathymetric range of 43 selected key marine species along the Mediterranean Sea coasts using the Reef Check Mediterranean Underwater Coastal Environment Monitoring (RCMed U-CEM) protocol. The taxa, including algae, invertebrates, and fishes, were selected by a combination of criteria, including ease of identification and being a key indicator of shifts in the Mediterranean subtidal habitats due to local pressures and climate change. The presence and abundance of gas bubbles leaching from the seabed are also recorded. The dataset collected using the RCMed U-CEM protocol is openly accessible across different platforms and allows for various uses. It has proven to be useful for several purposes, such as monitoring the ecological status of Mediterranean coastal environments, assessing the effects of human impacts and management interventions, as well as complementing scientific papers on species distribution and abundance, distribution modeling, and historical series. Also, volunteers’ commitment promotes marine stewardship and environmental awareness in marine conservation. Here, we describe the RCMed U-CEM protocol, from training volunteers to recording, delivery, and sharing data, including the quality assurance and control (QA/QC) procedures.

A sediment bypassing plant based on innovative jet pump, ejectors, has been tested in the first-of-a-kind demo application at the harbor of Cervia (Italy, Northern Adriatic Sea). The ejector is a jet pump aimed to reduce sediment accumulation in navigation channels and coastal areas. Herein we present results of the first study assessing the potential ecological effects of the ejectors plant. Sediment characteristics, benthic, and fish assemblages before and after the plant activation have been analyzed in the putatively impacted (the sediment removal and discharge) areas and four control locations, one time before and two times after plant activation. Ejectors plant operation resulted in a reduction of the mud and organic matter content in the sediment, as well as in changes in shell debris amount in the impacted areas. Abundance and species richness of benthic macroinvertebrates, initially reduced in the impacted areas, probably due to the previous repeated dredging, returned to higher values during demo plant continuous operation. Higher diversity of fish fauna was observed in the study area during plant operation period. Observed dynamics of the ecological status of the marine habitat suggest that an ejectors plant could represent an eco-friendly solution alternative to dredging operations to solve harbor siltation problems.

Mediterranean gorgonian forests are species-rich habitats, and like many other marine habitats they are threatened by anthropogenic disturbances and mass mortality events. These mortality events have often been linked to anomalies in the temperature profiles of the Mediterranean region. On 5 September 2017, colonies of the gorgonians Eunicella singularis and Eunicella cavolini exhibited rapid tissue loss, down to a depth of 30 m along the steep cliffs of Montecristo Island, Tuscan Archipelago National Park, Tyrrhenian Sea, Italy. Interestingly, Montecristo has previously been identified as a reference site for the ecological quality assessment of the western Mediterranean benthic assemblages on rocky bottoms. The observed mortality event occurred during a period of increased sea temperature. By utilising a combination of high-resolution oceanographic analysis, forecast models and citizen science initiatives, we propose that an early warning system for the concomitance of heat waves and mortality events can be put in place. A temperature-based coral disease surveillance tool could then be established for the entire Mediterranean Sea. Such a tool would allow for the timely study of mass mortality phenomena and the implementation of prompt mitigation and/or restoration initiatives. Finally, this specific mortality event, in a Marine Protected Area, offers a unique opportunity to monitor and assess the resilience of gorgonian populations and associated benthic assemblages in the absence of other, more directly, anthropogenic disturbances such as pollution and land runoff.