Search

The present study, based on microsatellite markers, describes a population genetic analysis of the small-spotted catshark Scyliorhinus canicula (Linnaeus, 1758), representing one of the most abundant and commonly caught cartilaginous fishes in the Mediterranean Sea and adjacent areas. The analyses were performed to unravel the genetic features (variability, connectivity, sex-biased dispersal) of their relative geographic populations, both at the small (around the coast of Sardinia, Western Mediterranean Sea) and at a larger spatial scale (pan-Mediterranean level and between the Atlantic Ocean and the Mediterranean Sea). Individual clustering, multivariate and variance analyses rejected the hypothesis of genetic homogeneity, with significant genetic differences mainly within the Mediterranean between the Western and Eastern basins, as well as between the Mediterranean and the NE Atlantic Ocean. In detail, our results seem to confirm that the Strait of Gibraltar could not represent a complete barrier to the exchange of individuals of small-spotted catshark between the Atlantic Ocean and the Mediterranean Sea. In the latter area, a complex genetic structuring for S. canicula was found. Apart from differences among the Western, Eastern and Adriatic sites, within the Western basin the small-spotted catsharks around Sardinian waters are strongly differentiated from all others (both from the eastern Tyrrhenian Sea and southernmost part of the Algerian basin) and are demographically stable. Several possible mechanisms, both biological and abiotic (e.g., migratory behavior, waterfronts, and oceanographic discontinuities), are discussed here to explain their peculiar characteristics. Overall, the genetic data presented, both at the local and regional level, could represent a baseline information, useful for the temporal monitoring of populations, and to assess the effects of present or future fishing/management/conservation measures.

In 1990s, the European spiny lobster

Effectiveness of restocking programs in Marine Fully Protected Areas' (FPAs) can be highly affected by the movement behavior of the species to protect. We analyzed the data of 744 Palinurus elephas specimens tagged, relocated inside 12 FPAs, established in the seas surrounding Sardinia (central-western Mediterranean), and then recaptured. The overall aims were to characterize the individuals' movements after the relocation and to discuss strengths and weaknesses of the current FPAs' design. Almost 80% of tagged individuals travelled progressively increasing distances, as a function of the release distance, up to a maximum value of 11,500 m. Then, for larger release distances, individuals' mobility appeared reduced and more chaotic. A similar trend was found analyzing the distances travelled with respect to the FPAs with the highest number of recaptured individuals and to the size. These results allow to establish a threshold limit of the release distance, to take into account when designing FPAs, as a useful tool to keep a portion of the individuals into FPAs' borders, in order to both preserve the species and guarantee a spillover of individuals in the commercial areas.

Simple Summary Four rare species are recognized within the genus Tremoctopus (Cephalopoda: Octopoda), i.e., T. gelatus, T. gracilis, T. robsoni, and T. violaceus. The accurate identification of organisms is a fundamental prerequisite to deepen our knowledge of the biology and ecology of a species. In this study, for the first time, an integrative morphological and genetic approach was undertaken to confirm the identity of specimens of the genus Tremoctopus collected in Mediterranean waters. Sequences of two mitochondrial genes were generated and analyzed from three Mediterranean females, allowing ascribing all the samples to the species T. violaceus sensu stricto. For the first time, barcoding sequences have been obtained from the presumed type locality of the species. This information is of particular importance for this rare species; it has been complemented with the detailed descriptions of morphometric and biological features, as well as beaks analyses for the age estimation of the samples. Abstract An integrative approach based on morphological and genetic analyses was undertaken for the first time to confirm the species identification of Mediterranean samples belonging to the genus Tremoctopus. Sequences of two mtDNA genes (cytochrome c oxidase subunit (COI) and 16S) were generated for the first time from Mediterranean samples. Both the similarity-based identifications and tree-based methods indicated that three females can be identified as Tremoctopus violaceus sensu stricto in agreement with their morphological classifications. All Mediterranean sequences clustered with the sequences of Tremoctopus violaceus from the Gulf of Mexico and were clearly differentiated from the sequences attributed to T. gracilis and T. robsoni. The chromatic pattern of the web and some features of gill filaments, arms formula, stylets, radulae, beaks, and stomach contents were given for all the samples; 105,758, 20,140, and 11,237 oocytes were estimated in the mature, immature, and developing samples, respectively. The presence of four spermatangia inside the cavity of the maturing female suggested the ability of this species to mate before reaching full maturity with more partners. Age investigation using beaks, performed for the first time in T. violaceus and within the genus gave results consistent with the different sizes and maturity conditions of the samples.

Fully Protected Areas (FPAs) represent a powerful tool for marine resources management. Among the parameters to consider for their optimal design, the movements of the species to protect are of particular importance. We examined the movement patterns of744 spiny lobsters, Palinurus elephas, tagged during a restocking program carried out in 12 Sardinian FPAs. Once the lobsters were captured, tagged, transported and released in the center of the FPA, the linear distances performed by 80% of the lobsters from the recapture (RC) to the release point (RE), (recapture distance, RC-RE) increased as a function of the point in which they were captured for the first time (release distance, C-RE), until a maximum value of about 13500 m. By a management perspective, these results highlight a behaviour, perhaps attributable to homing, representing an important starting point to take into consideration when planning FPAs. In fact, since release and recapture distances appeared related, in order to preserve a portion of the lobsters within the FPA and to guarantee a spillover of specimens in the surrounding commercial areas, the longer is the release, the bigger would be the FPA.

The precious red coral, Corallium rubrum, and the yellow gorgonian, Eunicella cavolini, have been frequently reported as co-occurring species in the deep Mediterranean Sea. However, knowledge regarding spatial distribution of the two species in the deep sea is still fragmented, as well as potential drivers of their co-occurrence. This study aims to provide data on the status of deep-dwelling red coral populations, which are now the main target of commercial harvesting, study the demography of the yellow gorgonian in the deep sea, and finally analysing their variability when co-occur. Both species exhibited the highest population density at deeper depths and the presence of an inverse relationship between population density and colony height. We found a high percentage (40% on average) of red coral harvestable colonies (> 10 mm basal diameter), as well as of living colonies (77% as average). Our study evidenced that most of co-occurring colonies were found below 130 m depth. Red coral density did not significantly vary with the presence of E. cavolini, whereas the yellow gorgonian showed significant higher density when co-occur with red coral, even if with lower height. Distance-based linear modelling (DistLM) revealed that red coral density significantly influenced the presence of the yellow gorgonian, emphasizing the need for proper conservation strategies of red coral populations in order to preserve habitat complexity and associated diversity.

Marine animal forests are important mesophotic habitats threatened by an increasing number of natural and human pressures. Although several international agreements aim to protect these vulnerable ecosystems, the Environmental Status of most of these benthic animal-structured habitats remains unknown. Based on ROV footage, we evaluated the Environmental Status of 5 black corals forests in the center of the Western Mediterranean Sea, through the Mesophotic Assemblages Conservation Status (MACS) Index. The MACS index combines two independent indices: the Index of Status of the benthic communities, analyzing conspicuous species diversity, basal layer and canopy composition; the Index of Impact, analyzing siltation level, canopy condition and marine litter occurrence. The five investigated sites are characterized by the presence of two Antipatharians, Antipathella subpinnata and Leiopathes glaberrima, dwelling in different environmental conditions. Four sites showed high and good values of the Index of Status, and only one site showed a moderate status. Regarding the Impact Index, four sites were classified with low values, except one showed a very low value. Overall, four black forests were classified in a Good and one in a Very High Environmental Status. Assessing the Environmental Status is the first step needed to monitor these essential habitats’ health over time and improve the current frameworks for their conservation and protection, such as the Marine Strategy Framework Directive

12 pages, 3 figures, supplementary information https://doi.org/10.1038/s41559-019-1091-z.-- The dataset generated and analysed during the current study is available from the corresponding author on reasonable request, The deep sea (>200 m depth) encompasses >95% of the world’s ocean volume and represents the largest and least explored biome on Earth (, This work was supported by the H2020 project MERCES (GA N. 689518) and IDEM (GA N. 11.0661/2017/750680/SUB/EN V.C2.). E.R.-L. was supported by the Norwegian project MarMine (247626), the Norwegian Institute for Water Research and the H2020 project MERCES (GA N. 689518). P.V.R.S. was supported by the NSERC Canadian Healthy Oceans Network and CFREF Ocean Frontier Institute. L.T. is supported by JPI Oceans2 and ONC. J.A. is supported by ARIM (Autonomous Robotic sea-floor Infrastructure for bentho-pelagic Monitoring; MartTERA ERA-Net Cofound). L.L. acknowledges NSF grant OCE 1634172 and the Deep-Ocean Observing Strategy subcontract from the Consortium for Ocean Leadership. H.R. was supported by the EMSO-Link project of the European Commission (Grant agreement ID: 731036), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Meiofaunal abundance, assemblage structure and richness of higher taxa were investigated for the first time in two submarine canyons (Polcevera and Bisagno) of the Ligurian Sea and along the adjacent open slope, in relation with the quantity and quality of sedimentary organic matter and other environmental variables, including grain size. Meiofaunal abundance and richness of higher taxa decreased with increasing water depth (from ca. 200 down to ca. 2000-m depth) in the open slope and Polcevera canyon, whereas the highest values were observed at 500 m depth in the Bisagno canyon. The comparison between canyons and the adjacent open slope, showed the lack of significant differences in meiofaunal abundance, at the same depth except for samples collected at 200 and 2000-m depth. Overall the biodiversity was higher in canyons than in the open slope. Phytopigments, utilised as a proxy of the input of primary organic matter, were up to 3 times higher in canyon than in slope sediments and, along with grain size, explained a large portion of the variability in all meiofaunal variables. Canyon and slope showed a high beta diversity (83%), mostly due to the presence of a high portion of rare taxa in the canyons. Some taxa, such as Cladocera, Cumacea, Gastrotricha, Nemertina were exclusively encountered in canyon sediments, whereas Tardigrada were encountered only in the adjacent slope. Results reported here indicated that, differences in meiofaunal assemblages between canyons and slopes are primarily driven by quantity and quality of the available food resources and by the presence of specific topographic features.

Living (Rose-Bengal stained) benthic foraminifera were investigated in eleven stations sampled along transects following a depth gradient from Polcevera and Bisagno canyons and the adjacent open slope (Ligurian Sea), in a depth interval ranging from 200 to 2000 m. In order to understand which environmental factors influence the abundance and taxonomical composition of the foraminiferal assemblages in these two domains (canyon and open slope), qualitative and quantitative foraminiferal data were correlated to the sediment biochemical composition (in terms of phytopigments, proteins, lipids, carbohydrates and biopolymeric carbon), grain size and the main hydrological characteristics (salinity, temperature, dissolved oxygen). The Cluster Analysis and Canonical Correspondence Analysis allowed us to detect two sectors (coastal and offshore) characterized by contrasting trophic conditions. The coastal sector reflects spread meso-eutrophic conditions in both physiographic domains being possibly more impacted by the river inputs and sediment transport processes from land. In fact, the narrow continental shelf of the Ligurian Sea favors the deposition of sediment transported by riverine processes on the immediately adjacent coastal areas. As a result homogenization of sea-bottom conditions occurs, leading to an unclear differentiation between open slope and canyon foraminiferal assemblages. Conversely, the offshore sector is less affected by physical disturbance due to the sedimentary flows decreasing in relation to the larger distance from the coastline. Consequently, the lower organic matter content and lower food quality (expressed in terms of contribution of the primary material to the biopolymeric carbon pool) lead to a more oligotrophic condition, which favors the development of peculiar assemblages dominated by Glomospira charoides, Ammolagena clavata and epifaunal taxa. The first finding ever of a warm tropical species (Amphistegina lessonii) in the Ligurian Sea sediments at 500-m depth can be considered the first evidence of upward expansion of tropical species to the Northern portion of the Mediterranean Sea, which is experiencing an evident water warming linked to the ongoing global climate change.

In 1990s, the European spiny lobster Palinurus elephas, one of the most commercially important species in the Mediterranean, exhibited a population decline. For this reason, fully protected areas (FPAs) appeared effective in re-establishing natural populations and supporting fishery-management objectives. Here, the reproductive parameters of P. elephas populations in two different FPAs (Su Pallosu and Buggerru, central-western Mediterranean), where a restocking programme was carried out, and in their surrounding commercial zones, were investigated from quantitative and qualitative perspectives. The comparison of fecundity between females collected inside and outside FPAs did not show statistical differences as well as the vitellogenin concentration, which did not vary among eggs of different size classes of females caught inside and outside the FPAs, indicating the same reproductive potential. The study demonstrated a benefit of overexploited populations in terms of enhancement of egg production overtime (15 years for Su Pallosu and 6 years for Buggerru) with a mean egg production 4.25–5.5 times higher at the end of the study than that observed at the beginning of the study. The main driver of eggs production appeared to be size, with larger lobsters more present inside the FPAs than outside. Given these results, the dominant contribution of the two studied FPAs to the regional lobster reproduction is remarkable.

14 pages, 6 figures, 1 table, supplementary material https://www.frontiersin.org/articles/10.3389/fmars.2021.626843/full#supplementary-material, Restoration is considered an effective strategy to accelerate the recovery of biological communities at local scale. However, the effects of restoration actions in the marine ecosystems are still unpredictable. We performed a global analysis of published literature to identify the factors increasing the probability of restoration success in coastal and marine systems. Our results confirm that the majority of active restoration initiatives are still concentrated in the northern hemisphere and that most of information gathered from restoration efforts derives from a relatively small subset of species. The analysis also indicates that many studies are still experimental in nature, covering small spatial and temporal scales. Despite the limits of assessing restoration effectiveness in absence of a standardized definition of success, the context (degree of human impact, ecosystem type, habitat) of where the restoration activity is undertaken is of greater relevance to a successful outcome than how (method) the restoration is carried out. Contrary to expectations, we found that restoration is not necessarily more successful closer to protected areas (PA) and in areas of moderate human impact. This result can be motivated by the limits in assessing the success of interventions and by the tendency of selecting areas in more obvious need of restoration, where the potential of actively restoring a degraded site is more evident. Restoration sites prioritization considering human uses and conservation status present in the region is of vital importance to obtain the intended outcomes and galvanize further actions., Research funded by the EU project MERCES of the European Union's Horizon 2020 research (Grant agreement No. 689518, http://www.merces-project.eu)., Research funded by the EU project MERCES of the European Union's Horizon 2020 research (Grant agreement No. 689518, http://www.merces-project.eu)

2 pages.-- Reply to: Ecological variables for deep-ocean monitoring must include microbiota and meiofauna for effective conservation, J. Ingels et al. Nature Ecology & Evolution 5: 27-29 (2021), doi: 10.1038/s41559-020-01335-6, Meiofauna and microbes are key components of deep-sea ecosystem assessments and were included among the list of essential variables in our recent comprehensive assessment and prioritization of a global deep-ocean monitoring and conservation strategy1. Meiofauna ranked in the top three variables, whereas microbes (bacteria, and archaea) were reported as key variables for some aspects of monitoring the deep sea. However, larger components of the deep-sea fauna (such as macro- and megafauna) received the highest priority. In their Matters Arising, Ingels and co-workers2 criticized the ranking because, in their opinion, macro- and megafaunal components cannot be considered higher-priority variables than microbes and meiofauna. They concluded that this result reflects an unequal distribution of the competence of the authors and of the respondents to the elicitation survey. However, their criticisms are unjustified for conceptual, methodological and operational reasons. On semantic and theoretical grounds, Ingels et al. confused the concept of priority with that of relevance/importance. Ingels et al. seem also to confound the concept of monitoring and protecting with the importance of research for advancing scientific knowledge; these are two partly related, but distinct, objectives. Indeed, recognizing the ecological importance of one biological component is one thing, but identifying the monitoring variables where capacity to deliver for conservation management globally is well established, is quite another. We cannot apply the same monitoring and conservation approach to all biological components because small organisms, such as prokaryotes, protists and meiofauna encompass massive numbers of undescribed species with largely unknown ecologies3,4 and shorter turnover times, which may make them more resilient to disturbance than larger biota. Even an ocean completely depleted of large fauna, for example, sharks and all predators, would remain flush with meiofauna and microbes. Yet, a deep-sea system with abundant meiofauna and prokaryotes would almost certainly function poorly without higher trophic levels. This well-known ecological principle is certainly one of the reasons there was a wide consensus among the 112 experts (including the microbiologists and meiofauna experts who participated in the expert elicitation) on censusing larger species to protect vulnerable habitats they inhabit or create. The much more limited evidence for microbial and meiofaunal endemicity, the great proportion of unidentified species and the lack of life-history information, greatly compromise any proposal to use these components as proxies for monitoring and mapping conservation areas. Thus, the results of the expert elicitation, on the one hand, reflect the maturity of the disciplines and the capability to deliver indicator information and, on the other hand, recognize the role of larger organisms in current conservation priorities, while acknowledging fundamental roles of all groups., Another important aspect overlooked by Ingels et al. is that deep-sea biodiversity was only one of the five main research areas addressed by the study. In the second research area we considered, which was dedicated to ecosystem functions, benthic faunal biomass and benthic faunal production were ranked as top variables (see table 1 in Danovaro et al.1). Because meiofauna and microbes typically dominate benthic faunal biomass at abyssal depths5,6, we took care to emphasize the functional role of microbial components: “microbes (primarily bacteria followed by archaea) largely dominate overall biomass and production. These microscopic components, essential for deep-sea ecosystem functions … we stress microbial heterotrophic and chemoautotrophic C production as two essential ecological variables needed for understanding the key processes sustaining the functioning of deep-sea food webs and biogeochemical cycles”. We also strongly disagree with the methodological criticisms of Ingels et al. As scientists, we endeavour to remove all potential sources of bias in the framework of standard good practices for data evaluation. Our study is based on expert elicitation, which is a procedure to find consensus on priorities, not an experiment with treatments and controls; thus, standard deviations cannot be treated as in ecological experimental designs. Our Perspective describes how we endeavoured to achieve an objective methodology (that is, coverage of different research fields and knowledge for each of the five main themes, scientists covered a broad range of geographic regions, different taxonomic expertise, academic qualifications and years of experience). These aspects, including statistical treatment, were discussed in detail using multiple rounds of enquiries, following rigorous procedures7, and were presented transparently in the supplementary information of our paper1. To our knowledge, the 112 scientists participating in this elicitation make this study the widest deep-sea community ever to participate in defining priorities based on standardized questions. Ingels et al. assumed that microbial and meiofaunal components were not prioritized because most of the respondents were macrofaunal or megafaunal experts. However, this is not evident in our data, because a large fraction of respondents covered multiple fields of expertise (note that the supplementary information1 reported only one main topic per scientist). Their criticism suggests that deep-sea scientists are divided into two groups: micro- meiofaunal experts competing against macro- megafaunal experts, fighting to prioritize their own work, rather than a community working together towards a common objective. Obtaining expert opinions for comprehensive deep-sea management, as we did, requires the involvement of scientists working in different sectors (such as deep-sea technologies, conservation biology, biological oceanography, biogeochemistry, policy and management), thus participants cannot simply be classified as experts by faunal size category. The fact that many scientists, in responding to the questionnaire, did not automatically prioritize their own research specialty for deep-ocean monitoring, conservation and impact assessment suggests that this is a false and non-productive dichotomy. Accordingly, we reaffirm that the expert elicitation reported in Danovaro et al.1 is robust, accurate and balanced, and simply reflects the prioritization of the groups of organisms/habitats and associated variables to monitor in light of anthropogenic impacts, conservation needs and currently available technology, feasibility and knowledge. In operational terms, environmental monitoring, especially in the deep sea, requires ready-to-use technologies and methods that are employable, which greatly influences the choice of monitoring priorities and rankings of the consulted experts. Our paper innovatively coupled this need with the readiness levels of the described technologies. We agree that the scientific community should do more to document the importance of small organisms, to establish and disseminate the best standardized practices for collecting such observations and to increase our knowledge of undescribed species and their ecological roles to use them more effectively in future monitoring plans, particularly in light of the ongoing effects of global change8,9,10. At the same time, no marine protected area (in both shallow waters and in the open ocean) or other conservation initiative anywhere targets the loss of meiofaunal or microbial diversity. The reference to the Marine Strategy Framework Directive (MSFD 2008/56/EC), designed to address the Good Environmental Status of marine ecosystems (including the deep sea), does not support the position of Ingels et al.2 as the analysis of deep-sea biodiversity in the MSFD is, at present, limited to species of commercial interest and deep-water corals. None of the European directives prioritize meiofauna or microbes. Moreover, to the best of our knowledge, there is no single ongoing, nor planned, monitoring strategy of a national agency based on or prioritizing microbial or meiofaunal diversity in their standard protocols. Given the current limitation in the use of high-throughput sequencing (for example, for the identification of meiofauna3), further efforts are thus necessary to better integrate microbes and meiofauna in future monitoring and conservation programmes. To do this, the global deep-sea community must encourage joint efforts, share common goals and use standardized tools, This work was supported by the H2020 projects MERCES (Grant agreement no. 689518), and IDEM (Grant agreement no. 11.0661/2017/750680/SUB/EN V.C2.), by the Norwegian Institute for Water Research, by the NSERC Canadian Healthy Oceans Network and CFREF Ocean Frontier Institute, by JPI Oceans2 and ONC, by ARIM (MartTERA ERA-Net Cofound), by NSF grant OCE 1634172, by DOOS from the Consortium for Ocean Leadership, by the EMSO-Link EU project (Grant agreement ID: 731036) and by the Faculty of Science RAE Improvement Fund of The University of Hong Kong, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

The white skate Rostroraja alba is assessed by the International Union for Conservation of Nature as Endangered globally and is now considered rare in the Mediterranean. This species has never been recorded in Sardinian seas (central western Mediterranean), but an empty eggcase was collected on a sandy bottom off the western Sardinia coasts during the MEDiterranean International Trawl Survey (MEDITS) program in 2019. A morphometric and morphological description of the Sardinian eggcase, after a comparison with measurements from other Mediterranean and Atlantic specimens, showed it to be clearly ascribable to Rostroraja alba.

Habitat heterogeneity is a major structuring agent of benthic assemblages promoting high turnover in species composition and ultimately contributing to overall higher diversity. Submarine canyons, a pervasive feature of the continental margins worldwide, increase habitat heterogeneity at multiple spatial scales. In the present study, we test the hypothesis that different topographic structures or/and food sources controlling the abundance, biomass and biodiversity (using meiofauna and nematodes as a model study) in canyon systems. To do so, we compared different topographic structures: canyon edge, thalweg and axis, and the upper shelf and open slope in the Gulf of Gioia (Gioia and Petrace Canyons) and in the Gulf of Naples (Dohrn Canyon) (Tyrrhenian Sea) at different depths. Our results suggest that meiofaunal abundance and biomass are generally higher in the canyon thalwegs than in the canyon edge or adjacent open slopes at regional scale. This pattern is not always confirmed for biodiversity and when thalwegs are compared to different topographic structures within the Gioia Canyon system. In our study, the role of food quantity and quality is preeminent to explain the spatial distribution of meiofaunal variables among different topographic structures at 200-m while habitat heterogeneity become relevant at 500-m and within the Dohrn Canyon. In Gioia and Petrace Canyons we observed a high food availability is associated to specific topographic structures (thalwegs) that influenced the meiofaunal abundance and diversity distribution and nematode diversity and species composition. Each topographic structure shows a high number of exclusive species that contributes to a high species turnover and high overall biodiversity in all canyon systems. Changes in nematode composition determine also differences in the functional diversity (trophic guilds composition) and life strategy of the nematode assemblages. Our findings reveal that the presence of different topographic structures influences the spatial distribution of food quality and quantity that determine the presence of exclusive taxa and species enhancing both local and regional diversity.

International audience; In a world of declining biodiversity, monitoring is becoming crucial. Molecular methods , such as metabarcoding, have the potential to rapidly expand our knowledge of biodiversity, supporting assessment, management, and conservation. In the marine environment, where hard substrata are more difficult to access than soft bottoms for quantitative ecological studies, Artificial Substrate Units (ASUs) allow for standardized sampling. We deployed ASUs within five regional seas (Baltic Sea, Northeast Atlantic Ocean, Mediterranean Sea, Black Sea, and Red Sea) for 12-26 months to measure the diversity and community composition of macroinvertebrates. We identified invertebrates using a traditional approach based on morphological characters, and by metabarcoding of the mitochondrial cytochrome oxidase I (COI) gene. We compared community composition and diversity metrics obtained using the two methods. Diversity was significantly correlated between data types. Metabarcoding of ASUs allowed for robust comparisons of community composition and diversity, but not all groups were successfully sequenced. All locations were significantly different in taxonomic composition as measured with both kinds of data. We recovered previously known regional biogeographical patterns in both datasets (e.g., low species diversity in the Black and Baltic Seas, affinity between the Bay of Biscay and the Mediterranean). We conclude that the two approaches provide complementary information and that metabarcoding shows great promise for marine monitoring. However, until its pitfalls are addressed, the use of metabarcoding in monitoring of rocky benthic assemblages should be used in addition to classical approaches rather than instead of them.

Breakwaters are man-made constructions utilized for preventing coastal erosion primarily from wave action. At the same time, defence structures, modifying currents and circulation can affect water quality and benthic assemblages. Assessing and minimizing the impact of these structures is a priority in human-modified coastal ecosystems, such as the central northern Adriatic where breakwaters extend for hundreds of kilometres. We investigated the effects of breakwater relocation on benthic features and meiofaunal diversity. To do this, we conducted a before–after comparison of (2011–2017) the relocation, which occurred in 2015. The analysis was conducted comparing a sheltered site, characterized by the presence of seagrass meadows and a wave-exposed site. Sediment features and meiofaunal variables were altered by the relocation, especially in the areas colonized by seagrass meadows. Results presented here pointed out to an enrichment in organic matter, the loss of two sensitive taxa (Cumacea and Ostracoda) and a shift in the assemblage structure with the increase of the relevance of Copepoda and Polychaeta. These results indicate that the careful management of breakwater is crucial for planning adequate conservation practices and protecting seagrass habitats and their biodiversity.

Corallium rubrum and Eunicella cavolini are two octocorals, reported as co-occurring species in the deep rocky habitats of the Mediterranean Sea with a high hydrodynamic and moderate eutrophication. Their spatial distribution and demography in the deep sea are mainly affected by temperature and direct and indirect anthropogenic activities; however, knowledge of the factors that potentially influence their co-existence is scarce. This paper provides novel data on the distribution and demography of these two species, at depths between 50 and 290 m in the Western Mediterranean Sea, providing insights on their co-occurrence. Both species exhibited the highest population density at deeper sites (>150 m), showing an inverse size–density relation. Density values ranged from 0.03 colonies m−2 to 32 and 80 col. m−2 for yellow gorgonian and red coral, respectively. The two species co-occurred in 13% of the total frames examined, mostly dwelling between 120 and 160 m depth. Distance-based linear modeling (DistLM) emphasized that when co-occurring the variability of the two species’ densities were significantly driven by the density—rather than the morphology (i.e., height)—of the other species. We stress the need for further studies to elucidate the possible mutual effects of suspension feeders and to test the role of different environmental factors potentially influencing inter-specific relationships.

The cumulative impact of microplastic and organic enrichment is still largely unknown. Here, we investigated the microplastic contamination, the organic enrichment and their effects on meiofaunal distribution and diversity in two islands of the Maldivian archipelago: one more pristine, and another strongly anthropized. Field studies were coupled with manipulative experiments in which microplastic polymers were added to sediments from the non-anthropized island (i.e., without organic enrichment) to assess the relative effect of microplastic pollution on meiofauna assemblages. Our results reveal that the impact of microplastic contamination on meiofaunal abundance and taxa richness was more significant in the anthropized island, which was also characterized by a significant organic enrichment. Meiofauna exposed experimentally to microplastic contamination showed: i) the increased abundance of opportunistic nematodes and copepods and ii) a shift in the trophic structure, increasing relevance in epistrate-feeder nematodes. Based on all these results, we argue that the coexistence of chronic organic enrichment and microplastics can significantly increase the ecological impacts on meiofaunal assemblages. Since microplastic pollution in the oceans is predicted to increase in the next decades, its negative effects on benthic biodiversity and functioning of tropical ecosystems are expected to worsen especially when coupled with human-induced eutrophication. Urgent actions and management plans are needed to avoid the cumulative impact of microplastic and organic enrichment.

Marine litter is an ever-increasing problem that demands immediate reduction plans and mitigation actions that should act synergically to efficiently meet ambitious goals. Since the seafloor has been recognized as the major sink for marine debris, the study of litter accumulation dynamics represent a fundamental tool to evaluate possible removal actions. We analysed a 7 years (2013–2019) standardized data series collected along Sardinian fishing grounds through MEDiterranean International Trawl Survey, for which estimates of density and weight of seafloor macro-litter were calculated for over 707 hauls. Results show the absence of any temporal trend in seafloor macro-litter density and weight, but rather indicate a spatial and bathymetric segregation of different litter categories. Our data showed how different sources and physical features of macro-litter items (i.e., plastic and fishing gear, rubber, glass, metals, and cloth) led to spatially segregated accumulation hotspots. We also point out here how the identification of seafloor macro-litter hotspots using aggregated data that include plastic items could obscure the identification of other segregated but yet relevant hotspots of other macro-litter categories accumulated in the marine environment. These hotspots often occurred at shallower depths and closer to coastlines, thus representing potential spots where eventual future litter removal action could be prioritized.

Whole-genome sequence data were produced from a single flathead grey mullet female and assembled into a draft genome sequence, whereas publicly available sequence data were used to obtain a male draft sequence. Two pools, each consisting of 60 unrelated individuals respectively of male and female fish were analysed using Pool-Sequencing. Mapping and analysis of Pool-Seq data against the draft genome(s) revealed >30 loci potentially associated with sex. The most promising of these loci encoding the follicle stimulating hormone receptor (FSHR) and harbouring two missense variants, was genotyped on 245 fish from four Mediterranean populations. Genotype data showed that FSHR represents a previously unknown sex-determining locus. However, the incomplete association pattern between FSHR genotype and sex-phenotype, the variability of such pattern across different natural populations and the presence of other candidate loci suggest a greater complexity underling sex determination in the flathead grey mullet.

Seafloor macrolitter is ubiquitous in world's oceans; still, huge knowledge gaps exist on its interactions with benthic biota. We report here the colonization of plastic substrates by the Mediterranean red coral Corallium rubrum (L. 1758), occurring both in controlled conditions and in the wild at ca. 85 m depth in the Western Mediterranean Sea. Juveniles settled on seafloor macro-litter, with either arborescent or encrusting morphology, ranging from 0.6 to 3.5 mm in basal diameter and 0.2–7.1 years of age, also including a fraction (20%) of potentially sexually mature individuals. In controlled conditions, larvae settled and survived on plastic substrates for >60 days. Our insights show that marine plastic debris can provide favourable substrate for C. rubrum settlement either in controlled conditions or in the wild, suggesting their possible use in restoration activities. However, we pinpoint here that this potential benefit could result in adverse effects on population dynamics.

Carbon dioxide capture and storage (CCS), involving the injection of CO2 into the sub-seabed, is being promoted worldwide as a feasible option for reducing the anthropogenic CO2 emissions into the atmosphere. However, the effects on the marine ecosystems of potential CO2 leakages originating from these storage sites have only recently received scientific attention, and little information is available on the possible impacts of the resulting CO2-enriched seawater plumes on the surrounding benthic ecosystem. In the present study, we conducted a 20-weeks mesocosm experiment exposing coastal sediments to CO2-enriched seawater (at 5000 or 20,000 ppm), to test the effects on the microbial enzymatic activities responsible for the decomposition and turnover of the sedimentary organic matter in surface sediments down to 15 cm depth. Our results indicate that the exposure to high-CO2 concentrations reduced significantly the enzymatic activities in the top 5 cm of sediments, but had no effects on subsurface sediment horizons (from 5 to 15 cm depth). In the surface sediments, both 5000 and 20,000 ppm CO2 treatments determined a progressive decrease over time in the protein degradation (up to 80%). Conversely, the degradation rates of carbohydrates and organic phosphorous remained unaltered in the first 2 weeks, but decreased significantly (up to 50%) in the longer term when exposed at 20,000 ppm of CO2. Such effects were associated with a significant change in the composition of the biopolymeric carbon (due to the accumulation of proteins over time in sediments exposed to high-pCO2 treatments), and a significant decrease (∼20–50% at 5000 and 20,000 ppm respectively) in nitrogen regeneration. We conclude that in areas immediately surrounding an active and long-lasting leak of CO2 from CCS reservoirs, organic matter cycling would be significantly impacted in the surface sediment layers. The evidence of negligible impacts on the deeper sediments should be considered with caution and further investigated simulating the intrusion of CO2 from a subsurface source, as occurring during real CO2 leakages from CCS sites.

This paper investigated the long-term changes (from 1973 to 2013) of the seagrass meadows of Zostera marina, Zostera noltei and Cymodocea nodosa in the Adriatic Sea subjected to multiple pressures. We examined the changes of the meadows by means of field data collection, observations and analysis of aerial photography to identify the most important drivers of habitat loss. The major decline of seagrass extension observed from 1973 to 1989, was primarily driven by urban development, and by the increase of the blue tourism. From 1989 to 2007 seagrass habitats progressively recovered due to the decrease of urbanization, but from 2007 to 2013 a further significant loss of seagrass meadows was apparently driven by thermal anomalies coupled with an increasing anthropogenic pressure. Our long-term analysis provides evidence that the rates of seagrass loss are faster than the recovery rates (i.e., -4.5 loss rate vs +2.5% recovery rate per year).

Breakwaters are man-made constructions utilized for preventing coastal erosion primarily from wave action. At the same time, defence structures, modifying currents and circulation can afect water quality and benthic assemblages. Assessing and minimizing the impact of these structures is a priority in human-modifed coastal ecosystems, such as the central northern Adriatic where breakwaters extend for hundreds of kilometres. We investigated the efects of breakwater relocation on benthic features and meiofaunal diversity. To do this, we conducted a before–after comparison of (2011–2017) the relocation, which occurred in 2015. The analysis was conducted comparing a sheltered site, characterized by the presence of seagrass meadows and a wave-exposed site. Sediment features and meiofaunal variables were altered by the relocation, especially in the areas colonized by seagrass meadows. Results presented here pointed out to an enrichment in organic matter, the loss of two sensitive taxa (Cumacea and Ostracoda) and a shift in the assemblage structure with the increase of the relevance of Copepoda and Polychaeta. These results indicate that the careful management of breakwater is crucial for planning adequate conservation practices and protecting seagrass habitats and their biodiversity.

We investigated organic matter (OM) quantity, nutritional quality and degradation rates, as well as abundance and biodiversity of meiofauna and nematodes along the deep continental margin off Spitsbergen, in the Svalbard Archipelago. Sediment samples were collected in July 2010 and 2011 along a bathymetric gradient between 600 m and 2000 m depth, and total mass flux measured at the same depths from July 2010 to July 2011. In both sampling periods sedimentary OM contents and C degradation rates increased significantly with water depth, whereas OM nutritional quality was generally higher at shallower depths, with the unique exception at 600 m depth in 2010. Meiofaunal abundance and biomass (largely dominated by nematodes) showed the highest values at intermediate depths (ca 1500 m) in both sampling periods. The richness of meiofaunal higher taxa and nematode species richness did not vary significantly with water depth in both sampling periods. We suggest here that patterns in OM quantity, C degradation rates, and meiofauna community composition in 2011 were likely influenced by the intensification of the warm West Spitsbergen Current (WSC). We hypothesize that the intensity of the WSC inflow to the Arctic Ocean could have an important role on benthic biodiversity and functioning of deep-sea Arctic ecosystems.

4th World Conference on Marine Biodiversity (WCMB 2018), 13-16 May 2018, Montreal, A review of 573 studies on active restoration actions in the marine environment, published in the last 25 years, was carried out at global scale. We assessed how, where, at which spatial and temporal scales and under which socio-ecological settings restoration studies have been carried out, from very shallow to deep sea habitats. Results show that restoration efforts across habitats are increasing, especially in seagrasses and coral reefs, but never approached at ecosystem level. Targets, methods, response variables and standards are still very heterogeneous. Of the factors considered in the review, habitat, human impact intensity, realm and methods of restoration were found to be good determinant of restoration success. 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 this impairing long-term success stories. 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. Marine restoration is a promising approach to limit habitat loss. More science is needed to increase the number of success stories

Beach nourishment is a widely utilized solution to counteract the erosion of shorelines, and there is an active discussion on its possible consequences on coastal marine assemblages. We investigated the impact caused by a small-scale beach nourishment carried out in the Western Adriatic Sea on macrofaunal recruitment and post-settlement events. Artificial substrates were deployed in proximity of nourished and non-manipulated beaches and turbidity and sedimentation rates were measured. Our results indicate that sedimentation rates in the impacted site showed a different temporal change compared to the control sites, suggesting potential modifications due to the beach nourishment. The impact site was characterized by subtle changes in terms of polychaete abundance and community structure when compared to controls, possibly due to beach nourishment, although the role of other factors cannot be ruled out. We conclude that small-scale beach nourishments appear to be an eco-sustainable approach to contrast coastal erosion.

The deep sea is the largest biome of the biosphere. The knowledge of the spatial variability of deep-sea biodiversity is one of the main challenges of marine ecology and evolutionary biology. The choice of the observational spatial scale is assumed to play a key role for understanding processes structuring the deep-sea benthic communities and one of the most typical features of marine biodiversity distribution is the existence of bathymetric gradients. However, the analysis of biodiversity bathymetric gradients and the associated changes in species composition (beta diversity) typically compared large depth ranges (with intervals of 500 to 1000 or even 2000 m depth among sites). To test whether significant changes in alpha and beta diversity occur also at fine-scale bathymetric gradients (i.e., within few hundred-meter depth intervals) the variability of deep-sea nematode biodiversity and assemblage composition along a bathymetric transect (200–1200 m depth) with intervals of 200 m among sampling depths, was investigated. A hierarchical sampling strategy for the analysis of nematode species richness, beta diversity, functional (trophic) diversity, and related environmental variables, was used. The results indicate the lack of significant differences in taxonomic and functional diversity across sampling depths, but the presence of high beta diversity at all spatial scales investigated: between cores collected from the same box corer (on average 56%), among deployments at the same depth (58%), and between all sampling depths (62%). Such high beta diversity is influenced by the presence of small-scale patchiness in the deep sea and is also related to the large number of rare or very rare species (typically accounting for >80% of total species richness). Moreover, the number of ubiquitous nematode species across all sampling depths is quite low (ca. 15%). Multiple regression analyses provide evidence that such patterns could be related to the different availability, composition and size spectra of food particles in the sediments. Additionally, though to a lesser extent, our results indicate, that selective predation can influence the nematode trophic composition. These findings suggest that a multiple scale analysis based on a nested sampling design could significantly improve our knowledge of bathymetric patterns of deep-sea biodiversity and its drivers.

Carbon dioxide capture and storage (CCS), involving the injection of CO

Marine organisms belonging to meiofauna (size range: 20–500 μm) are amongst the most abundant and highly diversified metazoans on Earth including 22 over 35 known animal Phyla and accounting formore than 2/3 of the abundance ofmetazoan organisms. In anymarine system,meiofauna play a key role in the functioning of the food webs and sustain important ecological processes. Estimates of meiofaunal biodiversity have been so far almost exclusively based on morphological analyses, but the very small size of these organisms and, in some cases, the insufficient morphological distinctive features limit considerably the census of the biodiversity of this component. Molecular approaches recently applied also to small invertebrates (including meiofauna) can offer a new momentum for the census of meiofaunal biodiversity. Here, we provide an overview on the application of metagenetic approaches based on the use of next generation sequencing platforms to study meiofaunal biodiversity, with a special focus on marine nematodes. Our overview shows that, although such approaches can represent a useful tool for the census of meiofaunal biodiversity, there are still different shortcomings and pitfalls that prevent their extensive use without the support of the classical taxonomic identification. Future investigations are needed to address these problems and to provide a goodmatch between the contrasting findings emerging from classical taxonomic and molecular/bioinformatic tools.

1. The Mediterranean starry ray (Raja asterias) populations within the Mediterranean Sea are susceptible to high rates of bycatch in the multispecies trawl fisheries. Understanding its population structure and identifying critical habitats are crucial for assessing species vulnerability and setting the groundwork for specific management measures to prevent population decline. 2. To assess the population structure of R. asterias in the Mediterranean, the genetic variation in nine population samples at one mitochondrial marker and eight nuclear microsatellite loci was analysed. Moreover, 172 egg cases collected in the Strait of Sicily were identified at species level using integrated molecular and morphological approaches. 3. Genetic analyses revealed that the Mediterranean starry ray comprises three distinct units inhabiting the western, the central-western, and the central-eastern areas of the Mediterranean. An admixture zone occurs in the Strait of Sicily and the Ionian Sea, where individuals of the central-western and central-eastern population units intermingle. 4. The joint morphometric–genetic analyses of rajid egg cases confirmed the presence of more than one species in the admixture area, with a predominance of egg cases laid by R. asterias. DNA barcoding revealed that egg cases and embryos of R. asterias shared several haplotypes with adult individuals from the centralwestern and central-eastern Mediterranean Sea, revealing that females of both populations laid numerous eggs in this area. 5. According to these findings, detailed taxonomic determination of egg cases, when combined with seasonal migration studies, could improve the capability to identify important spawning or nursery areas for the Mediterranean starry ray, particularly in those admixture zones relevant to maintaining genetic diversity. 6. Finally, these new insights should be considered to update the Action Plan for the Conservation of Cartilaginous Fishes in the Mediterranean Sea with effective measures to reduce the impact of skate bycatch in trawling and safeguard egg cases in nursery areas.