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Spatial uptake patterns of microplastics (MP) by marine species are largely unexplored under field conditions. A novel “biodeposit trap” that measure uptake and egestion of MP by suspension-feeders through the analysis of their biodeposits, was designed and used to estimate the spatial variation of these processes by mussels in field conditions. Traps containing wild or farmed mussels or control empty shells were deployed at three sites characterised by different MP concentrations and water flow conditions. A different MP dimensional composition was observed between MP pools present in biodeposit and control traps, with the latter shifted towards higher dimensional range (0.05–5 mm). Conversely, mussels accumulated small MP (0.02–0.05 mm) into their biodeposits without any significant difference between wild and farmed specimens. MP uptake rates were on average 4–5 times higher at the site where MP contamination was expected to be highest and where water flow conditions were considered moderate.

51 pages, 6 figures, Global change is striking harder and faster in the Mediterranean Sea than elsewhere, where high levels of human pressure and proneness to climate change interact in mod- ifying the structure and disrupting regulative mechanisms of marine ecosystems. Rocky reefs are particularly exposed to such environmental changes with ongoing trends of degradation being impressive. Due to the variety of habitat types and associated marine biodiversity, rocky reefs are critical for the functioning of marine ecosystems, and their decline could profoundly affect the provision of essential goods and services which human populations in coastal areas rely upon. Here, we provide an up-to-date overview of the status of rocky reefs, trends in human-driven changes undermining their integrity, and current and upcoming management and conservation strategies, attempting a pro- jection on what could be the future of this essential component of Mediterranean marine ecosystems.

International audience

International audience; Canopy-forming algae are declining globally due to multiple disturbances. This decline has recently been on the increase due to the spread of some tropical herbivorous fishes. This new phenomenon has drawn attention to the effects of fish herbivory in temperate areas, which have been assumed to be negligible compared to that of invertebrates, such as sea urchins. In this study, the impact of a Mediterranean native herbivorous fish (Sarpa salpa, salema) was assessed on the canopy-forming seaweed Cystoseira amentacea var. stricta. Cystoseira amentacea forms belts in the infralittoral fringe of wave-exposed shores, which has so far been considered a refuge from fish herbivory. To test the effects of salema feeding on natural C. amentacea belts, an innovative herbivore deterrent device was conceived. Salema had a significant effect on C. amentacea by decreasing algal size, biomass and fertility, by up to 97%. The results suggest that the contribution of salema feeding to the loss of Cystoseira forests in the Mediterranean may have been overlooked. In addition, the analysis of temporal and spatial patterns of salema landings in the Mediterranean Sea suggests that salema abundance may have increased recently. Thus, along with invertebrate herbivory and anthropogenic stressors, fish herbivory may also represent a potential threat to algal forests in temperate areas.

Salt marshes are known for providing several essential ecosystem services, including coastal protection via wave attenuation and sediment stabilization. Despite their value, the global extent of salt marshes is decreasing due to human pressures, such as land reclamation, climate change and eutrophication, which are primary drivers of change in salt marsh ecosystems. We determined the factors affecting resistance to erosion in salt marshes of the Italian Northern Adriatic coast by subjecting salt marsh sediment cores to simulated wave treatment in wave mesocosms and estimating volume loss with novel photogrammetry techniques. In our first experiment investigating the influence of vegetation and sediment properties on erosion, our results showed that Spartina spp. salt marsh vegetation, and its root biomass in particular, enhances resistance to erosion, and this effect is stronger in sandy compared to silty soils. In a second experiment, we investigated the impacts of increased eutrophication on resistance to erosion by manipulating nutrients in one of our study sites (Grado Lagoon). Spartina spp. below-ground biomass significantly reduced erosion in nutrienttreated plots. Species composition in fertilized plots also shifted from Spartina spp. to Salicornia spp. succulents. Our study demonstrates the critical role of salt marsh vegetation in resistance to erosion, and how the effect of vegetation is mediated by sediment and nutrient conditions, raising important considerations for management of salt marshes for coastal protection.

Habitat-forming species sustain biodiversity and ecosystem functioning in harsh environments through the amelioration of physical stress. Nonetheless, their role in shaping patterns of species distribution under future climate scenarios is generally overlooked. Focusing on coastal systems, we assess how habitat-forming species can influence the ability of stress-sensitive species to exhibit plastic responses, adapt to novel environmental conditions, or track suitable climates. Here, we argue that habitat-former populations could be managed as a nature-based solution against climate-driven loss of biodiversity. Drawing from different ecological and biological disciplines, we identify a series of actions to sustain the resilience of marine habitat-forming species to climate change, as well as their effectiveness and reliability in rescuing stress-sensitive species from increasingly adverse environmental conditions.

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In the Mediterranean Sea Cystoseira forests are locally threatened due to several impacts. The low dispersal capacity of most Cystoseira species makes the natural recovery unlikely. The restoration of Cystoseira forests can represent a valuable solution and is recommended where the historical presence is recorded and the impacts that led to its loss are no longer acting (a reasoned forestation could be considered also where historical data are not available). MPAs may play a paramount role in the conservation of Cystoseira forests, guaranteeing protection from several impacts and representing the source of propagules for the restoration of lost or degraded forests outside their borders. MPAs where Cystoseira forests are lacking due to past impacts should be considered as priority experimental sites for artificial forestation.

Rapidly growing populations and expanding development are intensifying pressures on coastal ecosystems. Sea-level rise and other predicted effects of climate change are expected to exert even greater pressures on coastal ecosystems, exacerbating erosion, degrading habitat, and accelerating shoreline retreat. Historically, society’s responses to threats from erosion and shoreline retreat have relied on armoring and other engineered coastal defenses. Despite widespread use on all types of shorelines, information about the ecological impacts of shoreline armoring is quite limited. Here we summarize existing knowledge on the effects of armoring structures on the biodiversity, productivity, structure, and function of coastal ecoystems.

Coastal seascapes are modified to cope with human needs of development and shoreline protection. Coastal defense structures (CDS, e.g. breakwaters, seawalls, groynes) represent a common approach for coastal protection despite their ecological impacts (e.g. habitat degradation, changes in natural assemblages, spread of alien species). We examined the feasibility of enhancing the ecological value of CDS by facilitating the growth of species with conservation value, such as the canopy-forming macroalgae of the genus Cystoseira. Canopy habitats are globally threatened, and some Mediterranean species of Cystoseira are protected. Previous work suggested that artificial substrata may not represent adequate habitats for some species of Cystoseira. We used caging and transplant experiments to test 1) whether CDS provide habitats comparable to natural reefs for two species, C. barbata and C. compressa, and, if not, 2) whether a different grazing pressure might explain the different performance in the two habitats. Experimental units consisted of limestone plates on which either of the species had recruited naturally. Eight plates for each species were transplanted to each of three CDS and natural sites interspersed along the coast. Half of the plates at each site were caged to exclude grazers. Photographs were used to measure changes in cover of the two species in the different habitats and under different grazing pressures. Survival of either species was consistently enhanced by caging on CDS, where virtually no Cystoseira grew uncaged. There were some effects of grazing also in natural habitats, but these were more variable among sites and never completely hindered the growth of either species. We conclude that grazing can be a relevant factor in differentiating CDS from natural habitats. Understanding the different ecological processes in CDS is a key step towards preserving biodiversity and ecosystem services in marine environments increasingly occupied by artificial substrata.

International audience; Human-made structures are increasingly found in marine coastal habitats. The aim of the present study was to explore whether urban coastal structures can affect the genetic variation of hard-bottom species. We conducted a population genetic analysis on the limpet Patella caerulea sampled in both natural and artificial habitats along the Adriatic coast. Five microsatellite loci were used to test for differences in genetic diversity and structure among samples. Three microsatellite loci showed strong Hardy-Weinberg disequilibrium likely linked with the presence of null alleles. Genetic diversity was significantly higher in natural habitat than in artificial habitat. A weak but significant differentiation over all limpet samples was observed, but not related to the type of habitat. While the exact causes of the differences in genetic diversity deserve further investigation, these results clearly point that the expansion of urban structures can lead to genetic diversity loss at regional scales.

This is the first global assessment of the distribution and condition of bivalve shellfish reefs that occur in temperate and subtropical estuaries. The assessment is focused primarily on biogenic reefs formed by oysters within their native ranges, but also includes observations aboutmussels that formbeds and provide other ecosystemservices.We compiled quantitative and qualitative data about these reefforming species frompublished literature as well as expert surveys and direct observations and derived condition estimates for oyster reefs in 144 estuaries and 40 ecoregions around the world. Based on these data, we conclude that oyster reefs are one of, and likely themost, imperiledmarine habitat on earth: oyster reefs are in poor condition, defined as having declined >90%fromhistoric levels, in 70%of bays and 63%ofmarine ecoregions. Even more troubling, oyster reefs are functionally extinct (>99% loss of reefs) in 37%of estuaries and 28%of ecoregions. Globally, we estimate that 85% of oyster reefs have been lost—even greater than the losses reported for other important habitats including coral reefs,mangroves, and seagrasses. Although oyster reefs are beginning to receive some conservation attention, they remain an obscure ecosystemcomponent and still are vanishing at sometimes alarming rates. Many threats that have contributed to the profound loss of reefs around the world continue largely unabated today. Destructive fishing practices that directly alter the physical structure of reefs have been implicated in rapid declines in both fisheries productivity and overall reef condition in many estuaries. Fishing practices involving translocation and introduction of non-native shellfish within and between bays has increased the incidence and severity of disease and parasite outbreaks that have all but eliminated fisheries in many coastal areas. Coastal development activities including filling (“land-reclamation”) and dredging of shipping channels have also taken a toll on reefs. Likewise, activities occurring upstreamcontinue to cause problems as human populations increase in coastal watersheds. Altered river flows, construction of dams, poorlymanaged agriculture, and urban development can all impact the quality and quantity of water and sediments that affect whether shellfish reefs persist or perish. There are many things that can and should be done to address this glaring gap inmarine conservation.We identify a series of cost-effective strategies that can help turn the tide. No one strategy will be right for each area or threat and it is assumed thatmultiple strategies will be needed inmost places. The strategies are grouped into five themes: • Improve Protection for reefs of native shellfish; • Restore and Recover Reefs back to functioning ecosystems that providemultiple services to humans; • Manage Fisheries Sustainably for ecosystems and livelihoods; • Stop the Intentional Introduction and Spread of Nonnative Shellfish; and • ImproveWaterQuality

The structure, distribution and temporal changes of epibenthic assemblages of Mediterranean coralligenous reef in the Ligurian and Adriatic Sea were investigated by using a multifactorial sampling design. The distribution of taxa were analysed at scales ranging form hundred of meters to tens of kilometres. Temporal variations were analysed among different years. Percentage cover of conspicuous species have been analysed by means of photographic sampling. Strong spatial patterns of taxa distribution were found among coralligenous outcrops in the Adriatic, while in the Ligurian Sea a strong small scale pattern related to habitat orientation was found. There was some temporal fluctuation in abundance of taxa, but no clear patterns were observed. These results suggest that coralligenous assemblages are a patchy habitat where changes in species composition and abundance can occur at a range of spatial scales, down to few meters, moreover, validate the assumption of the limited temporal variability in Mediterranean coralligenous reefs, possibly related to the slow growth rates of the most abundant taxa and the reduced seasonality of physical conditions.

Il volume è una monografia completa sulla flora e la vegetazione di tutte le lagune italiane. Il contributo è stato finalizzato nell'ambito del network Lagunet - Italian Network for Ecological Research in Coastal Zone and Transitional Areas Il volume è stato realizzato in inglese per permettere la massima diffusione internazionale

Sono stata invitata a tenere la Keynote introduction per la Session II: Effects of climate change mitigation and adaptation measures on marine biodiversity and the role of marine biodiversity in the mitigation of climate change effects.

We have reviewed estimates of large-scale trends in the distributions and status of Euro-Mediterranean coastal habitats. Conspicuous declines of coastal wetlands, seagrasses, biogenic reefs, and complex macroalgae have been observed in several countries. In some regions, most valuable habitats were already severely degraded or driven to virtual extinction well before 1900. Nowadays less than 15% of the coastline is considered in "good" condition. Those fragments of native habitats that remain are under threat, and their management is not informed by adequate knowledge of their distribution and status.

Hypoxia is one of the most important and faster spreading threats to marine life and its occurrence has significantly increased in the last century. The effects of hypoxia on marine organisms and communities has mostly been studied in light of the intensity of the disturbance but not a lot of attention has been given to its interaction with other stressors and the timing of its appearance. In this thesis I started to explore these topics through laboratory and manipulative field experiments. I studied the interactive effects of thermal stress and hypoxia on a European native bivalve species (Cerastoderma edule; Linnaeus, 1758 ) and a non native one (Ruditapes philippinarum; Adams & Reeve, 1850) through a laboratory experiment performed in the Netherlands. The non native species displayed a greater tolerance to oxygen depletion than the native one. The first field experiment was performed in an Italian brackish coastal lagoon (Pialassa Baiona) and tested the effects of different timing regimes of hypoxia on the benthic community. It emerged that the main factor affecting the community is the duration of the hypoxia. The ability of the communities to recover after repeated hypoxic periods was explored in the second manipulative field experiment. We imposed three different timing regimes of hypoxia on sediment patches in Pialassa Baiona and we monitored the changes of both the benthic and the microbial communities after the disturbances. The preliminary analyses of the data from this last work suggest that the experimental manipulations caused limited detrimental effects on the communities. Overall this thesis work suggests that the duration of hypoxic events, their repetitive nature and the associated thermal stress are key factors in determining their effects on the communities and that management measures should point towards a reduction of the duration of the single hypoxic periods more than their frequency.

The growing ecological awareness of Ocean Sprawl impacts is promoting the adoption of eco-engineering strategies to enhance the ecological performance of coastal infrastructures. Biomimicry, as an eco-engineering tool, aims to design infrastructure more suitable for wildlife by manipulating structural factors to mimic natural habitats. However, little is known about the extent to which natural and artificial substrates differ in their structure and to what extent such differences affect the biota. To fill these knowledge gaps and consequently design biomimetic surfaces, I initially explored how much physical structure diverges between various types of natural and artificial substrates and tested to what extent differences in physical structure and material composition affect the epibenthic communities. By mean of an in-field mensurative experiment and a systematic review coupled with a meta-analysis, I found that, although communities tended to differ between natural and artificial coastal habitats, both physical structure and material composition reported an overall mild effect on epibenthic communities. However, an informed choice of building material and an appropriate combination of multiple structural manipulations can promote ecological benefits at multiple levels, from increasing the ecological performance in situ to reducing the impacts during the production process. Thus, I combined my findings in a final experiment, still in progress, where I am testing the combined role of shape, brightness and inclination of biomimetic surfaces I have designed in producing benefits at multiple levels. Overall, I suggest that biomimicry has the potential to increase the ecological value of artificial habitats especially when a wide range of aspects is simultaneously considered. Indeed, none of the structural factors, individually, can fully mimic the “natural conditions” to effectively improve the ecological performance of the artificial substrates. This emphasizes the need to include in future works a multi-level perspective to fully achieve the great potential of biomimicry.

Microplastics (MP) are omnipresent contaminants in the marine environment. Ingestion of MP has been reported for a wide range of marine biota, but to what extent the uptake by organisms affects the dynamics and fate of MP in the marine system has received little attention. My thesis explored this topic by integrating laboratory tests and experiments, field quantitative surveys of MP distribution and dynamics, and the use of specialised analytical techniques such as Attenuated-Total-Reflectance- (ATR) and imaging- Fourier Transformed Infrared Spectroscopy (FTIR). I compared different methodologies to extract MP from wild invertebrate specimens, and selected the use of potassium hydroxide (KOH) as the most cost-effective approach. I used this approach to analyse the MP contamination in various invertebrate species with different ecological traits from European salt marshes. I found that 96% of the analysed specimens (330) did not contain any MP. As preliminary environmental analyses showed high levels of environmental MP contamination, I hypothesised that most MP do not accumulate into organisms but are rather fast egested. I subsequently used laboratory multi-trophic experiments and a long-term field experiment using the filter-feeding mussel Mytilus galloprovincialis and the detritus feeding polychaete Hediste diversicolor to test the aforementioned hypothesis. Overall, results showed that MP are ingested but rapidly egested by marine invertebrates, which may limit MP transfer via predator-prey interactions but at the same time enhance their transfer via detrital pathways in the sediments. These processes seem to be extremely variable over time, with potential unexplored environmental consequences. This rapid dynamics also limits the conclusions that can be derived from static observations of MP contents in marine organisms, not fully capturing the real levels of potential contaminations by marine species. This emphasises the need to consider such dynamics in future work to measure the uptake rates by organisms in natural systems.

The goal of this paper is to propose a screening method for assessing the environmental risk to aquatic systems in harbours worldwide. A semi-quantitative method is based on environmental pressures, environmental conditions and societal response. The method is flexible enough to be applied to 15 harbours globally distributed through a multinational test using standardised and homogenised open data that can be obtained for any port worldwide. The method emerges as a useful approach towards the foundation of a global environmental risk atlas of harbours that should guide the harbour sector to develop a more globally informed strategy of sustainable development.

Coastal areas have been transformed worldwide by urbanization, so that artificial structures are now widespread. Current coastal development locally depletes many native marine species, while offering limited possibilities for their expansion. Eco-engineering interventions intend to identify ways to facilitate the presence of focal species and their associated functions on artificial habitats. An important but overlooked factor controlling restoration operations is overgrazing by herbivores. The aim of this study was to quantify the effects of different potential feeders on Cystoseira amentacea, a native canopy-forming alga of the Mediterranean infralittoral fringe, and test whether manipulation of grazing pressure can facilitate the human-guided installation of this focal species on coastal structures. Results of laboratory tests and field experiments revealed that Sarpa salpa, the only strictly native herbivorous fish in the Western Mediterranean Sea, can be a very effective grazer of C. amentacea in artificial habitats, up to as far as the infralittoral fringe, which is generally considered less accessible to fishes. S. salpa can limit the success of forestation operations in artificial novel habitats, causing up to 90% of Cystoseira loss after a few days. Other grazers, such as limpets and crabs, had only a moderate impact. Future engineering operations,intended to perform forestation of canopy-forming algae on artificial structures, should consider relevant biotic factors, such as fish overgrazing, identifying cost-effective techniques to limit their impact, as is the usual practice in restoration programmes on land.

Climate-driven range-shifts create evolutionary opportunities for allopatric divergence and subsequent contact, leading to genetic structuration and hybrid zones. We investigate how these processes influenced the evolution of a complex of three closely related Cystoseira spp., which are a key component of the Mediterranean-Atlantic seaweed forests that are undergoing population declines. The C. tamariscifolia complex, composed of C. tamariscifolia s.s., C. amentacea and C. mediterranea, have indistinct boundaries and natural hybridization is suspected. Our aims are to (1) infer the genetic structure and diversity of these species throughout their distribution ranges using microsatellite markers to identify ancient versus recent geographical populations, contact zones and reproductive barriers, and (2) hindcast past distributions using niche models to investigate the influence of past range shifts on genetic divergence at multiple spatial scales. Results supported a single, morphologically plastic species the genetic structure of which was incongruent with a priori species assignments. The low diversity and low singularity in northern European populations suggest recent colonization after the LGM. The southern Iberian genetic hotspot most likely results from the role of this area as a climatic refugium or a secondary contact zone between differentiated populations or both. We hypothesize that life-history traits (selfing, low dispersal) and prior colonization effects, rather than reproductive barriers, might explain the observed genetic discontinuities. Pew Charitable Trusts (USA); MARINERA, Spain [CTM2008-04183-E/MAR]; FCT (Portugal) [FCT-BIODIVERSA/004/2015, CCMAR/Multi/04326/2013, SFRH/BPD/107878/2015, SFRH/BPD/85040/2012]; FPU fellowship of the Spanish Ministry of Education; European Community ASSEMBLE visiting grant [00399/2012]; University of Cadiz

Extensive development and construction in marine and coastal systems is driving a phenomenon known as “ocean sprawl”. Ocean sprawl removes or transforms marine habitats through the addition of artificial structures and some of the most significant impacts are occurring in sedimentary environments. Marine sediments have substantial social, ecological, and economic value, as they are rich in biodiversity, crucial to fisheries productivity, and major sites of nutrient transformation. Yet the impact of ocean sprawl on sedimentary environments has largely been ignored. Here we review current knowledge of the impacts to sedimentary ecosystems arising from artificial structures.\ud \ud Artificial structures alter the composition and abundance of a wide variety of sediment-dependent taxa, including microbes, invertebrates, and benthic-feeding fishes. The effects vary by structure design and configuration, as well as the physical, chemical, and biological characteristics of the environment in which structures are placed. The mechanisms driving effects from artificial structures include placement loss, habitat degradation, modification of sound and light conditions, hydrodynamic changes, organic enrichment and material fluxes, contamination, and altered biotic interactions. Most studies have inferred mechanism based on descriptive work, comparing biological and physical processes at various distances from structures. Further experimental studies are needed to identify the relative importance of multiple mechanisms and to demonstrate causal relationships. Additionally, past studies have focused on impacts at a relatively small scale, and independently of other development that is occurring. There is need to quantify large-scale and cumulative effects on sedimentary ecosystems as artificial structures proliferate. We highlight the importance for comprehensive monitoring using robust survey designs and outline research strategies needed to understand, value, and protect marine sedimentary ecosystems in the face of a rapidly changing environment.

The Mediterranean Sea is an enclosed basin connected to the Atlantic through the Strait of Gibraltar in the west and to the Sea of Marmara and the Black Sea through the Dardanelles in the east. Its surface waters cover 2,969,000 km2, which makes the Mediterranean the largest enclosed sea in the world (Bianchi and Morri, 2000). A recent analysis has estimated the occurrence of some 17,000 marine species in the Mediterranean, with taxa such as the Phaeophyta, Rhodophyta and Porifera including more than 10 per cent of the total number of species known globally (Coll et al., 2010). These figures are remarkable, considering that the Mediterranean Sea covers less than 1 per cent of the surface and volume of the world’s oceans. The origin of the highly diversified Mediterranean biota is relatively recent and is mainly derived from the Atlantic Ocean. The Mediterranean Sea has undergone various geological, climatic and hydrological transformations that have contributed to generate the hotspot of marine biodiversity that we see today (Bianchi and Morri, 2000; Coll et al., 2010; Lejeusne et al., 2010). In particular, isolation from theAtlantic during the Messinian crisis (6 Mya) resulted in strong evaporation with consequent dramatic changes in climate, sea level and salinity (Bianchi and Morri, 2000). The Messinian crisis decimated the biota of the ancient Mediterranean, which was largely dominated by Indo- Pacific species of warm-water affinities. When the connection with the Atlantic was reestablished (5 Mya), the newly colonising species mixed with those surviving the Messinian crisis. Alternating glacial and interglacial periods during the Quaternary, favouring the colonisation of boreal and subtropical species, further contributed to the diversification of the biota in the Mediterranean Sea. The opening of the Suez Canal in 1869 has also impacted on the native biodiversity of the Mediterranean through the introduction of new species from the Red Sea (Galil et al., 2014), which will likely increase in the near future following the expansion of the Suez Canal in 2015 (Galil et al., 2015b). There is a long tradition of descriptive studies in the Mediterranean Sea, with detailed accounts on taxonomic composition and regional patterns of distribution of marine organisms that exploded in the 1960s owing to intensifying oceanographic cruises and the advent of scuba diving (reviewed in Coll et al., 2010). Ourunderstanding of region-wide patterns of marine biodiversity in the Mediterranean Sea has increased considerably in the last fifteen years as a result of large-scale field surveys (Sala et al., 2011), extensive reviews of the literature (Bouillon et al., 2004; Danovaro et al., 2010; Martin and Giannoulaki, 2014; Telesca et al., 2015), modelling (Sarà et al., 2013; Marras et al., 2015) and synthesis of expert opinions (Micheli et al., 2013). This integration has generated new insights into the present distribution of the Mediterranean biota, as well as focussing attention on the main threats to marine biodiversity and the need to implement better conservation practices at the regional scale (Airoldi and Beck, 2007; Claudet and Fraschetti, 2010; Coll et al., 2010, 2012; Mouillot et al., 2011). In contrast to descriptive studies, experimental ecology has only been introduced recently in the Mediterranean, with an initial focus on biological interactions. The first experiment that incorporated the logical requirements of replication, randomisation and independence examined the effect of removing a canopy-forming alga in littoral rock pools (Benedetti-Cecchi and Cinelli, 1992a). A parallel study in the same system expanded the range of species interactions examined to include the effects of herbivory and competition between algal turfs (see Connell et al., 2014, for a clarification of the term turf ) and canopy recruitment (Benedetti-Cecchi and Cinelli, 1992b). Experimental work proliferated in the following years, examining species interactions in the context of ecological succession (Benedetti-Cecchi, 2000a, 2000b) and extending this approach to subtidal environments (Airoldi et al., 1995; Airoldi, 2000a). As we will discuss, some of these studies established the foundation for the theory that canopy-forming algae and turfs represent alternative states in shallow temperate rocky coasts under different disturbance and stress regimes (Airoldi, 1998, 2000b; Benedetti-Cecchi et al., 2001b), and that changes in sediment loads are one of the main triggers of these shifts in subtidal habitats (Airoldi et al., 1996; Airoldi and Cinelli, 1997; Airoldi, 2003; Irving et al., 2009). More recently, manipulations on subtidal rocky reefs have shown how low levels of herbivory in combination with the localincrease of nutrients may foster the recovery of macroalgal canopies and associated biota (Guarnieri et al., 2014). Experiments in the Mediterranean have also contributed to focus attention on the variance of ecological interactions (Benedetti-Cecchi, 2000c, 2003). Novel experimental designs have been developed that facilitate the separation of the effects of changing the mean intensity from the variance of biological interactions or any other spatially or temporally variable ecological process (Bertocci et al., 2005; Benedetti-Cecchi et al., 2006). These experiments revealed, for example, how spatial variance and mean intensity of grazing may interactively maintain spatially heterogeneous patterns of algal cover, illustrating the great potential for grazing to generate alternative states in marine benthic habitats (Benedetti-Cecchi et al., 2005). Motivated by the need to understand the effects of intensifying anthropogenic impacts and climate change on marine biodiversity, an increasing number of studies are now examining species interactions in relation to regional stressors and global threats such as ocean warming, acidification, extreme climate events and biological invasions (Bulleri et al., 2016). A better understanding of biotic interactions in the Anthropocene is also essential to guide habitat rehabilitation and restoration efforts. Here, we provide an overview of this type of research that will likely characterise future experimental research in the Mediterranean and elsewhere, using regime shifts as a conceptual framework to guide this approach. The concept of regime shifts, the abrupt transition between alternative states, unifies key aspects of species interactions and their responses to degrading environmental conditions, including resilience, early warning signals of collapse, extinction and hysteresis, all of which have direct bearing on environmental management. To achieve this, we start with a brief introduction to regime shifts and the underlying theory, followed by a discussion of ongoing regime shifts in the Mediterranean; such as the transition from macroalgal forests to turfdominated assemblages and the widespread collapse of sessile organisms in response to heatwaves, species invasions, infectious diseases andpest metabolites. We then examine the implications of threshold-like biological responses and hysteresis that are typically associated with regime shifts for habitat restoration and rehabilitation. Finally, we conclude with an overview of the research that is needed to understand the interplay between species interactions and rapid environmental change, for which the Mediterranean is providing several dramatic examples.

Conflicting interests, goals, and value often shape the stakeholders' positions concerning coastal erosion management strategies. Analyses of stakeholders' perceptions of beach nourishment and conflict management strategies are lacking. Since the involvement of key stakeholders is crucial to ensure successful integrated coastal management, the aim of the current study was to investigate the stakeholders' perceptions of beach nourishment and conflict management strategies in the community of the Portonovo Bay in the Adriatic Italian coast. During 2013, detailed, semi-structured interviews were conducted with members of the community and stakeholders regarding beach nourishment and related conflict management strategies at Portonovo Bay. The results revealed that respondents not only reported different perceptions, values, and interests but also their main goals were dissimilar. We found polarized opinions concerning antagonistic value systems shared by the participants, which were associated with quite opposed perceptions of existence and severity of the problem and efficacy and harmfulness of beach nourishment. The perceptions of the respondents were categorized into two major categories that reflect two of the philosophical views of the human-environment relationship: ecocentrism versus anthropocentrism. Four categories of proposed conflict resolution strategies were identified: (a) information, (b) dialogue and contact, (c) compromise, and (d) no solution. The adoption of a participatory approach and the implementation of conflict management skills and technique can be considered important elements of coastal management.

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Habitat-forming species sustain biodiversity and ecosystem functioning in harsh environments through the amelioration of physical stress. Nonetheless, their role in shaping patterns of species distribution under future climate scenarios is generally overlooked. Focusing on coastal systems, we assess how habitat-forming species can influence the ability of stress-sensitive species to exhibit plastic responses, adapt to novel environmental conditions, or track suitable climates. Here, we argue that habitat-former populations could be managed as a nature-based solution against climate-driven loss of biodiversity. Drawing from different ecological and biological disciplines, we identify a series of actions to sustain the resilience of marine habitat-forming species to climate change, as well as their effectiveness and reliability in rescuing stress-sensitive species from increasingly adverse environmental conditions. EuroMarine - European Marine Research Network

This study investigated the influence of physical and chemical conditions and biotic factors on the distribution and diversity of meiofauna in intertidal zone along a geographical gradient. At 11 sites along the Italian coast, we studied the concurring role of environmental variables, trophic resources and the presence of habitat-forming species (macroalgae vs. mussels) in controlling the meiofaunal communities. The increase of water temperature combined with local thermal conditions was associated with a decrease in nematodes and copepods, with a consequent decrease in meiofaunal abundance towards the south. However, the increase in salinity, as geographical gradient decreases, and local thermal conditions favoured the settlement of a greater number of taxa, influencing communities’ composition. The presence of macroalgae or mussels differently influenced the community structure of meiofauna on intertidal substrates and their response to environmental factors. From our results, the presence of macroalgae coverage appeared to reduce the impact of thermal stress on meiofauna and was associated with higher levels of meiofaunal diversity with respect to mussels. This work highlighted the importance of considering the interplay among biotic and abiotic factors, resulting in local combinations of environmental conditions, in order to understand the pattern of diversity and distributions of marine organisms.

Climate change is inducing shifts in species ranges across the globe. These can affect the genetic pools of species, including loss of genetic variability and evolutionary potential. In particular, geographically enclosed ecosystems, like the Mediterranean Sea, have a higher risk of suffering species loss and genetic erosion due to barriers to further range shifts and to dispersal. In this study, we address these questions for three habitat-forming seaweed species, Cystoseira tamariscifolia, C. amentacea and C. compressa, throughout their entire ranges in the Atlantic and Mediterranean regions. We aim to 1) describe their population genetic structure and diversity, 2) model the present and predict the future distribution and 3) assess the consequences of predicted future range shifts for their population genetic structure, according to two contrasting future climate change scenarios. A net loss of suitable areas was predicted in both climatic scenarios across the range of distribution of the three species. This loss was particularly severe for C. amentacea in the Mediterranean Sea (less 90% in the most extreme climatic scenario), suggesting that the species could become potentially at extinction risk. For all species, genetic data showed very differentiated populations, indicating low inter-population connectivity, and high and distinct genetic diversity in areas that were predicted to become lost, causing erosion of unique evolutionary lineages. Our results indicated that the Mediterranean Sea is the most threatened region, where future suitable Cystoseira habitats will become more limited. This is likely to have wider ecosystem impacts as there is a lack of species with the same ecological niche and functional role in the Mediterranean. The projected accelerated loss of already fragmented and disturbed populations and the long-term genetic effects highlight the urge for local scale management strategies that sustain the capacity of these habitat-forming species to persist despite climatic impacts while waiting for global emission reductions.

The intensity and frequency of climate-driven disturbances are increasing in coastal marine ecosystems. Understanding the factors that enhance or inhibit ecosystem resilience to climatic disturbance is essential. We surveyed 97 experts in six major coastal biogenic ecosystem types to identify “bright spots” of resilience in the face of climate change. We also evaluated literature that was recommended by the experts that addresses the responses of habitat-forming species to climatic disturbance. Resilience was commonly reported in the expert surveys (80% of experts). Resilience was observed in all ecosystem types and at multiple locations worldwide. The experts and literature cited remaining biogenic habitat, recruitment/connectivity, physical setting, and management of local-scale stressors as most important for resilience. These findings suggest that coastal ecosystems may still hold great potential to persist in the face of climate change and that local- to regional-scale management can help buffer global climatic impacts.

Changing climate threatens the structure and function of saltmarshes, which are often severely degraded by other human perturbations. Along the Mediterranean coastline, increasing temperature and decreasing rainfall have been hypothesised to trigger habitat shifts from perennial grasses to annual succulents in fragile saltmarsh ecosystems, such as those fringing the North Adriatic coastline. We used manipulative field experiments to investigate the effects of increased temperature, decreased precipitation and increased inundation period associated with rising sea levels on the dominant species in the lower marsh, the perennial grass Spartina spp. and the annual succulent Salicornia veneta. At ambient inundation, the combined effects of increased temperature and decreased precipitation enhanced soil temperature and decreased soil moisture, resulting in an increased number of plants, height and live biomass of S. veneta, as well as greater dead biomass of Spartina spp. compared with current conditions. Increased inundation reduced the soil redox potential, and resulted in losses of both Spartina spp. and S. veneta, but these negative effects were much more pronounced for S. veneta. An inundation tolerance test confirmed that S. veneta is significantly more vulnerable to rapid increases in inundation than Spartina spp. We conclude that at current inundation, the increasing drought conditions in the North Adriatic Sea are favouring the spread of the annual succulent S. veneta. The increasing spread of these succulents could reduce the future capability of the system to respond to projected increasing sea levels, as S. veneta is highly vulnerable to increased inundation. Synthesis. Our results highlight the complex interactions between different components of changing climate. Management strategies for saltmarshes in the Mediterranean and other microtidal locations facing similar changes in climate should focus on maintaining the freshwater and coastal channels free from blockages to ameliorate the effects of episodic drought/heatwave conditions and increasing the sediment supply and preventing coastal squeeze to enhance the resilience of the system to the continuous threat of sea level rise.

Canopy-forming seaweed species of the genus Cystoseira form diverse and productive habitats along temperate rocky coasts of the Mediterranean Sea. Despite numerous studies on the rich macrofauna and flora associated with Cystoseira spp., there is little knowledge about the epiphytic bacteria. We analyzed bacterial populations associated with canopies of Cystoseira compressa, over an annual vegetative cycle (May-October), and their relationships with the bacterial populations in the surrounding seawater, at intertidal rocky shores in Vasto (Chieti—Italy). The bacterial diversity was assessed using Illumina Miseq sequences of V1-V3 hypervariable regions of 16S rRNA gene. C. compressa bacterial community was dominated by sequences of Proteobacteria and Bacteroidetes, Verrucomicrobia, Actinobacteria, and Cyanobacteria especially of the Rhodobacteriaceae, Flavobacteriaceae, Sapropiraceae, Verrucomicrobiaceae, and Phyllobacteriaceae families. Seawater libraries were also dominated by Proteobacteria and Bacteroidetes sequences, especially of the Candidatus Pelagibacter (SAR11) and Rhodobacteriaceae families, but were shown to be clearly distinct from C. compressa libraries with only few species in common between the two habitats. We observed a clear successional pattern in the epiphytic bacteria of C. compressa over time. These variations were characterized by gradual addition of OTUs (Verrucomicrobia, Actinobacteria and SR1) to the community over a growing season, indicative of a temporal gradient, rather than a radical reorganization of the bacterial community. Moreover, we also found an increase in abundance over time of Rhodobacteraceae, comprising six potential pathogenic genera, Ruegeria, Nautella, Aquimarina, Loktanella, Saprospira, and Phaeobacter which seemed to be associated to aged thalli of C. compressa. These bacteria could have the potential to affect the health and ecology of the algae, suggesting the hypothesis of a possible, but still unexplored, role of the microbial communities in contributing to the extensive ongoing declines of populations of Cystoseira spp. in the Mediterranean Sea.

Marine canopy-forming seaweeds are among the most important habitat-forming species along temperate and polar rocky coasts. They form diverse, productive and valuable "forest" habitats that play a key role in coastal primary production, nutrient cycling and disturbance regulation, and facilitate abundant algae and animal communities. They are also some of the most heavily impacted coastal habitats, facing increasing pressures from urban sprawl, pollution, overfishing and climatic instabilities. Identifying the type and strength of interactions between multiple anthropogenic and natural stressors can help setting achievable management targets for degraded ecosystems and support ecological resilience through local actions. My research focuses primarily on understanding the effects of multiple local and global stressors on canopy-forming seaweeds of the genus Cystoseira, with and emphasis on field investigation and experimentation. I approached my research integrating different approaches: 1) I investigated which are the factors driving the loss of canopy-forming seaweeds at global level. The results allowed to detect important synergistic interactions between nutrient enrichment, caused mainly by human activities, and different other stressors such as heavy metals, the presence of competitors, low light and increasing temperature. This suggested that local management of nutrient levels would provide the greatest opportunity for preventing the shift from canopy to mat-forming algae; 2) as second step, I analysed the status of the intertidal Cystoseira populations around the Italian coast, and explored which factors are most likely to influence it. The results reported severe depletion of intertidal populations of Cystoseira, and identified urbanization as one of the main factors related to these poor conditions, confirming the need for urgent management actions to reduce human pressures on these valuable habitat forming species; 3) then, I experimentally investigated the effects of extreme events caused by climate change. I focused my attention on the effects of abrupt increases of air temperature caused by heat-wave events on the intertidal C. compressa around the Italian coast. The results indicated that extreme heat-wave negatively affect the photosynthetic activity of C. compressa, and that local biodiversity and thermal history of the alga seem to play a role reducing or increasing respectively the impact of such extreme events. 4) I also explored the possible overlooked role of the epiphytic bacteria growing on C. compressa. Bacteria can interact with seaweeds in symbiotic, pathological and opportunistic ways, modulating the health, performance and resilience of their hosts and could, therefore play a critical role on the responses of Cystoseira spp. to stress factors. I characterised for the first time the epiphytic bacteria associated to the surface of C. compressa using Illumina Miseq sequences of V1-V3 hypervariable regions of 16S rRNA gene, and investigated their seasonal variations and their relationships with the bacterial populations in the surrounding seawater. I found that bacterial populations associated to C. compressa were clearly distinct from those in the surrounding media, and identified a clear successional pattern, interestingly characterized by an increase in abundance of potential microbial pathogens associated to older thalli of C. compressa; 5) the previous quantitative descriptive work represented an important base-knowledge to further explore experimentally whether surface bacteria could influence the responses of their hosting Cystoseira populations to stressors. I analysed experimentally in the field the interacting effects of nutrient enrichment and heat-wave events on C. compressa population, and explored whether any resulting changes in the photosynthetic activity of C. compressa were associated to changes in the epiphytic bacterial communities. The heat wave caused marked declines of the photosynthetic activity of the intertidal C. compressa. These effects persisted for at least 3 hours, while recovery generally occurred after 24 hours. The heat-wave altered the structure of the epiphytic bacteria of C. compressa. Thalli exposed to the heat-wave presented an increase of OTUs previously shown to be associated with the natural degradation of the thalli of C. compressa, or implied in causing disease or damage to macroalgae. As observed for the photosynthetic activity, these differences decreased over time, suggesting that the microbial community has the ability to recover. Differently from previous work, this experiment did not detect significant effects related to nutrient enrichment, suggesting that the effects of nutrients could be context dependent. These results open new questions concerning the mechanisms by which the epibacterial community could influence the responses and future persistence of these important canopy-forming seaweeds.

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Conservation and environmental management are principal countermeasures to the degradation of marine ecosystems and their services. However, in many cases, current practices are insufficient to reverse ecosystem declines. We suggest that restoration ecology, the science underlying the concepts and tools needed to restore ecosystems, must be recognized as an integral element for marine conservation and environmental management. Marine restoration ecology is a young scientific discipline, often with gaps between its application and the supporting science. Bridging these gaps is essential to using restoration as an effective management tool and reversing the decline of marine ecosystems and their services. Ecological restoration should address objectives that include improved ecosystem services, and it therefore should encompass social–ecological elements rather than focusing solely on ecological parameters. We recommend using existing management frameworks to identify clear restoration targets, to apply quantitative tools for assessment, and to make the re-establishment of ecosystem services a criterion for success.

1. Artificial structures are sprawling in marine seascapes as a result of burgeoning coastal populations, increasing development and energy demand, and greater risks from climate change, storm surges and sea level rise. Interest in designing marine developments that maintain vital ecosystems and critical services is growing, but progress requires understanding the factors that influence the ecological performance of these novel artificial habitats. 2. We combined field observations and experiments along 500 km of the North Adriatic coastline to analyse the performance of artificial substrata as habitats to support canopyforming algae belonging to the genus Cystoseira, among the most ecologically relevant foundation species along rocky Mediterranean coastlines. We aimed to: clarify the underlying factors controlling the growth of Cystoseira in the artificial habitat ; contrast the relative importance of these factors between artificial and natural habitats ; and test the generality of the results across different sites and species of Cystoseira. 3. We found that: (i) the growth of canopy algae was significantly lower on artificial structures compared to rocky reefs ; (ii) such lower growth of canopy algae was not related to less favourable abiotic conditions but to higher biotic disturbance from both consumptive and nonconsumptive interactions on the artificial structures compared to the natural reef ; and iii) this was consistent across different study sites and canopy-forming species. 4. We conclude that biological factors influencing the growth of canopy algae, such as herbivory or other nonconsumptive disturbances, can differ substantially between artificial and natural habitats. The unusually large and previously unreported biotic pressure characterizing many artificial structures can negatively affect their performance as habitats to support ecologically relevant, foundation species. 5. Synthesis and applications. While nearly all considerations to improve the ecological performance of hard marine infrastructures focus on abiotic factors (e.g. construction materials, surface texture, habitat complexity or water quality), careful consideration of critical biotic factors is also needed to further progress the green engineering of sprawling marine infrastructures.

Expected increases in the frequency and intensity of storm surges and river flooding may greatly affect the relative salinity of estuarine environments over the coming decades. In this experiment we used detritus from three contrasting environments (marine Fucus vesiculosus; estuarine Spartina anglica; terrestrial Quercus robur) to test the prediction that the decomposition of the different types of litter would be highest in the environment with which they are associated. Patterns of decomposition broadly fitted our prediction: Quercus detritus decomposed more rapidly in freshwater compared with saline conditions while Fucus showed the opposite trend; Spartina showed an intermediate response. Variation in macro-invertebrate assemblages was detected along the salinity gradient but with different patterns between estuaries, suggesting that breakdown rates may be linked in part to local invertebrate assemblages. Nonetheless, our results suggest that perturbation of salinity gradients through climate change could affect the process of litter decomposition and thus alter nutrient cycling in estuarine transition zones. Understanding the vulnerability of estuaries to changes in local abiotic conditions is important given the need to better integrate coastal proceses into a wider management framework at a time when coastlines are increasingly threatened by human activities.

Natural systems face pressures exerted by natural physical-chemical forcings and a myriad of co-occurring human stressors that may interact to cause larger than expected effects, thereby presenting a challenge to ecosystem management. This thesis aimed to develop new information that can contribute to reduce the existing knowledge gaps hampering the holistic management of multiple stressors. I undertook a review of the state-of-the-art methods to detect, quantify and predict stressor interactions, identifying techniques that could be applied in this thesis research. Then, I conducted a systematic review of saltmarsh multiple stressor studies in conjunction with a multiple stressor mapping exercise for the study system in order to infer potential important synergistic stressor interactions. This analysis identified key stressors that are affecting the study system, but also pointed to data gaps in terms of driver and pressure data and raised issues for potentially overlooked stressors. Using field mesocosms, I explored how a local stressor (nutrient availability) affects the responses of saltmarsh vegetation to a global stressor (increased inundation) in different soil types. Results indicate that saltmarsh vegetation would be more drastically affected by increased inundation in low than in medium organic matter soils, and especially in estuaries already under high nutrient availability. In another field experiment, I examined the challenges of managing co-occurring and potentially interacting local stressors on saltmarsh vegetation: recreational trampling and smothering by deposition of excess macroalgal wrack due to high nutrient loads. Trampling and wrack prevention had interacting effects, causing non-linear responses of the vegetation to simulated management of these stressors, such that vegetation recovered only in those treatments simulating the combined prevention of both stressors. During this research I detected, using molecular genetic methods, a widespread presence of S. anglica (and to a lesser extent S. townsendii), two previously unrecorded non-native Spartinas in the study areas.

In the near future, the oceans will be subjected to a massive development of marine infrastructures, including offshore wind, tidal and wave energy farms and constructions for marine aquaculture. The development of these facilities will unavoidably exert environmental pressures on marine ecosystems. It is therefore crucial that the economic costs, the use of marine space and the environmental impacts of these activities remain within acceptable limits. Moreover, the installation of arrays of wave energy devices is still far from being economically feasible due to many combined aspects, such as immature technologies for energy conversion, local energy storage and moorings. Therefore, multi-purpose solutions combining renewable energy from the sea (wind, wave, tide), aquaculture and transportation facilities can be considered as a challenging, yet advantageous, way to boost blue growth. This would be due to the sharing of the costs of installation and using the produced energy locally to feed the different functionalities and optimizing marine spatial planning. This paper focuses on the synergies that may be produced by a multi-purpose offshore installation in a relatively calm sea, i.e. , the Northern Adriatic Sea, Italy, and specifically offshore Venice. It analyzes the combination of aquaculture, energy production from wind and waves, and energy storage or transfer. Alternative solutions are evaluated based on specific criteria, including the maturity of the technology, the environmental impact, the induced risks and the costs. Based on expert judgment, the alternatives are ranked and a preliminary layout of the selected multi-purpose installation for the case study is proposed, to further allow the exploitation of the synergies among different functionalities.

This study examined echinoderm assemblages from nearshore rocky habitats for large-scale distribution patterns with specific emphasis on identifying latitudinal trends and large regional hotspots. Echinoderms were sampled from 76 globally-distributed sites within 12 ecoregions, following the standardized sampling protocol of the Census of Marine Life NaGISA project ( www.nagisa.coml.org ). Sample-based species richness was overall low (2 cm in 1 m 2 quadrats) was highest in the Caribbean ecoregions and echinoids dominated these assemblages with an average of 5 ind m −2 . In contrast, intertidal echinoderm assemblages collected from clearings of 0.0625 m 2 quadrats had the highest abundance and richness in the Northeast Pacific ecoregions where asteroids and holothurians dominated with an average of 14 ind 0.0625 m −2 . Distinct latitudinal trends existed for abundance and richness in intertidal assemblages with declines from peaks at high northern latitudes. No latitudinal trends were found for subtidal echinoderm assemblages with either sampling technique. Latitudinal gradients appear to be superseded by regional diversity hotspots. In these hotspots echinoderm assemblages may be driven by local and regional processes, such as overall productivity and evolutionary history. We also tested a set of 14 environmental variables (six natural and eight anthropogenic) as potential drivers of echinoderm assemblages by ecoregions. The natural variables of salinity, sea-surface temperature, chlorophyll a , and primary productivity were strongly correlated with echinoderm assemblages; the anthropogenic variables of inorganic pollution and nutrient contamination also contributed to correlations. Our results indicate that nearshore echinoderm assemblages appear to be shaped by a network of environmental and ecological processes, and by the differing responses of various echinoderm taxa, making generalizations about the patterns of nearshore rocky habitat echinoderm assemblages difficult.