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Temperate rocky reefs often support mosaics of alternative habitats such as macroalgal forests, algal turfs and sea urchin barrens. Although the composition of epilithic microbial biofilms (EMBs) is recognized as a major determinant of macroalgal recruitment, their role in regulating the stability of alternative habitats on temperate rocky reefs remains unexplored. On shallow rocky reefs of the Island of Capraia (NW Mediterranean), we compared EMB structure among canopy stands formed by the fucoid Ericaria brachycarpa, algal turfs, and urchin barrens under ambient versus experimentally enhanced nutrient levels. The three habitats shared a core microbial community consisting of 21.6 and 25.3% of total ASVs under ambient and enhanced nutrient conditions, respectively. Although Gammaproteobacteria, Alphaproteobacteria and Flavobacteriia were the most abundant classes across habitats, multivariate analyses at the ASV level showed marked differences in EMB composition among habitats. Enhancing nutrient level had no significant effect on EMBs, although it increased their similarity between macroalgal canopy and turf habitats. At both ambient and enriched nutrient levels, ASVs mostly belonging to Proteobacteria and Bacteroidetes were more abundant in EMBs from macroalgal canopies than barrens. In contrast, ASVs belonging to the phylum of Proteobacteria and, in particular, to the families of Rhodobacteraceae and Flavobacteriaceae at ambient nutrient levels and of Rhodobacteraceae and Bacteriovoracaceae at enhanced nutrient levels were more abundant in turf than canopy habitats. Our results show that primary surfaces from alternative habitats that form mosaics on shallow rocky reefs in oligotrophic areas host distinct microbial communities that are, to some extent, resistant to moderate nutrient enhancement. Understanding the role of EMBs in generating reinforcing feedback under different nutrient loading regimes appears crucial to advance our understanding of the mechanisms underpinning the stability of habitats alternative to macroalgal forests as well as their role in regulating reverse shifts.

The mechanisms underpinning long-term dynamics and viability of invader populations in the receiving environment remain largely unknown. We tested the hypothesis that temporal variations in the abundance of a well-established invasive seaweed, Caulerpa cylindracea, in the NW Mediterranean, could be regulated by inter-annual fluctuations in environmental conditions. Abundance data of C. cylindracea, sampled repeatedly between 2005 and 2020 at the peak of its growing season (late summer/early fall), were related to interannual variations in seasonal seawater temperature, wind speed and rainfall recorded during different growth phases of the alga, in both subtidal and intertidal habitats. In both habitats, higher peak of C. cylindracea cover was associated with lower seawater temperature in spring and summer, when the seaweed exits the winter resting phase and starts a period of active growth. In addition, the peak abundance of subtidal C. cylindracea was positively associated with higher autumn wind speed intensity and spring daily total precipitation. Our study reveals the importance of seasonal and interannual variation of abiotic factors in shaping temporal patterns of abundance of C. cylindracea, in both subtidal and intertidal habitats. Identifying the factors underpinning invasive population temporal dynamics and viability is essential to predict the time and conditions under which an invader can thrive, and thus guide management strategies aimed to containing invasions under current and future climates.

Marine protected areas (MPAs) are a common management tool for preserving marine biodiversity and halting resource depletion. The number of MPAs is rapidly increasing worldwide to achieve the global targets agreed under the Convention on Biological Diversity. Nonetheless, MPAs often achieve their objectives only partially. In some cases – the so-called phenomenon of “paper parks” – protected areas totally fail to achieve their conservation targets. Therefore, identifying the factors underpinning MPA success or failure is crucial to increase their effectiveness. Here, we present the results of a global literature review of studies suggesting different strategies that managers should pursue in order to enhance MPA effectiveness. A search of the Scopus database, using strings of keywords connected by Boolean operators generated a batch of 715 items, out of which 68 were retained after the application of inclusion/exclusion criteria. Six other articles were added through the scanning of the literature cited in selected papers. We grouped MPA success-strategies into 13 main groups and ranked them according to the frequency of citation in the literature. Each group was further split into a series of actions and relative frequencies. Our findings identify stakeholder involvement, increasing communication and awareness between specific stakeholder groups, as well as ensuring appropriate enforcement and monitoring, control and surveillance, as the leading strategies for MPA success. Our results will assist in the process of upcoming global expansion of MPAs, thus contributing to improve conservation of marine biodiversity and associated livelihoods.

Urban infrastructures can provide 'novel' habitats for marine and terrestrial animals and plants, enhancing their ability to adapt to urban environments. In particular, coastal infrastructures characterized by a complex three-dimensional morphology, such as breakwaters, could provide species refuges and food. We investigated the role of breakwaters in providing habitat for vertebrates and plants, and the influence of anthropogenic litter in regulating the value of these structures as habitat. We sampled vertebrate and plant species and quantified the amount of anthropogenic litter on breakwaters and adjacent rocky habitats at several sites in three different countries (Italy, Spain and Chile). We found breakwaters to accumulate more litter items (e.g. especially plastics) than adjacent rocky habitats by means of their large-scale (i.e., 1 m) structural complexity. Birds, which used the artificial infrastructure as transitory habitat, reached similar abundances in breakwaters compared with adjacent rocky platforms. In contrast, synanthropic mammal species, such as Rattus norvegicus and feral cats, were slightly more frequent on breakwaters and appeared to use them as permanent habitat. Plants were frequent in the upper zone of breakwaters and, even though many macrophyte species can trap litter, their cover correlated negatively with anthropogenic litter density. Therefore, breakwaters provide either transitory or permanent habitats for different species, despite functioning as a sink for anthropogenic litter. Thus, new infrastructure should be designed with lower structural complexity in their supralittoral zone limiting the proliferation of synanthropic species. In addition, restricting public access to sensitive areas and enforcing littering fines could enhance the ecological value of these novel habitats by reducing the benefits to pest species.

The phylum Porifera and their symbionts produce a wide variety of bioactive compounds, playing a central role in their ecology and evolution. In this study, four different extracts (obtained by non-polar and semi-polar extraction methodologies) of the Mediterranean sponge Ircinia oros were tested through a multi-bioassay integrated approach to assess their antifouling potential. Tests were performed using three common species, associated with three different endpoints: the marine bacterium Aliivibrio fischeri (inhibition of bioluminescence), the marine diatom Phaeodactylum tricornutum (inhibition of growth), and different development stages of the brackish water serpulid Ficopomatus enigmaticus (gametes: sperm motion, vitality inhibition and cellular damage; larvae: development; adults: AChE (acetylcholinesterase)-inhibitory activity). The effects of extracts were species specific and did not vary among different extraction methodologies. In particular, no significant reduction of bioluminescence of A. fischeri was observed for all tested samples. By contrast, extracts inhibited P. tricornutum growth and had toxic effects on different F. enigmaticus’ developmental stages. Our results suggest that the proposed test battery can be considered a suitable tool as bioactivity screening of marine natural products.

Marine protected areas (MPAs) are a common management tool for preserving marine biodiversity and halting resource depletion. Despite the number of MPAs rapidly increasing worldwide, there are concerns over the full achievement of their objectives. Indeed, in some cases—the phenomenon of so-called “paper parks”—protected areas totally fail to achieve their conservation and socioeconomic targets. Therefore, identifying the factors underpinning MPA success or failure is crucial to increase their effectiveness. To achieve this goal, we performed a global literature review on the socioeconomic factors that managers should pursue to enhance MPA effectiveness on a global scale. A search of the Scopus database, using strings of keywords connected by Boolean operators, generated a batch of 715 items, out of which 68 were retained after the application of inclusion/exclusion criteria. Six other articles were added through the scanning of the literature cited in selected papers. We grouped MPA success-factors into 13 main groups and ranked them according to the frequency of citation in the literature. Our findings identify stakeholder involvement, increasing communication and awareness between specific stakeholder groups, as well as ensuring appropriate enforcement and monitoring, control and surveillance, as the leading factors for MPA success. Our results will assist in the process of upcoming global expansion of MPAs, thus contributing to improving conservation of marine biodiversity and associated livelihoods.

International audience; In this paper, we investigated the age distribution and dynamics of polyps in the slow-growing and long-lived gorgonian Corallium rubrum (the Mediterranean red coral), applying an a posteriori demographic approach by considering each colony as a population of polyps. In the Mediterranean red coral, new polyps emerge from the coenenchyme in different regions of the colony and their budding rate depends on the age of branches. The age of polyps, branches and colonies were estimated using the organic-matter-staining dating method on thin sections of the colony skeleton. The median age and maximum life span of polyps were 4 and 12 years suggesting the presence of senescence processes: thus a colony renews several times its polyps during life cycle. Polyps were divided into annual age classes, and their mortality rates calculated. The polyp age distribution was then used to construct a mortality table and an algebraic transition matrix based on the age at death of 234 polyps. Finally, the polyp budding rate of a young, unbranched colony was calculated, and polyp temporal dynamics simulated. These findings represent the first steps for developing demographic models able to describe polyp dynamics of old and highly branched colonies.

The rate of introduction of man-made habitats in coastal environments is growing at an unprecedented pace, as a consequence of the expansion of urban areas. Floating installations, due to their unique hydrodynamic features, are able to provide great opportunities for enhancing water detoxification through the use of sessile, filtering organisms. We assessed whether the application of sponges to floating pontoons could function as a tool for biomonitoring organic and inorganic pollutants and for improving water quality inside a moderately contaminated marina in the NW Mediterranean. Fragments of two common Mediterranean sponges (Petrosia (Petrosia) ficiformis and Ircinia oros) were fixed to either suspended natural fibre nets beneath a floating pontoon or to metal frames deployed on the sea bottom. We assessed the accumulation of organic and inorganic contaminants in sponge fragments and, in order to provide an insight into their health status, we examined changes in their metabolic and oxidative stress responses and associated microbiomes. Fragments of both sponge species filtered out pollutants from seawater on both support types, but generally showed a better physiological and metabolic status when fixed to nets underneath the pontoon than to bottom frames. P. (P) ficiformis maintained a more efficient metabolism and exhibited a lower physiological stress levels and higher stability of the associated microbiome in comparison with I. oros. Our study suggests that the application of sponges to floating pontoon represents a promising nature-based solution to improve the ecological value of urban environments.

Microplastic (MP) pollution represents a distinctive mark of the Anthropocene. Despite the increasing efforts to determine the ecological impacts of MP on marine biodiversity, our understanding of their toxicological effects on invertebrate species is still limited. Despite their key functional roles, sponges (Phylum Porifera) are particularly understudied in MP research. These filter-feeders extract and retain particles from the water column, across a broad size range. In this study, we carried out a laboratory experiment to assess the uptake of MPs (polyethylene, PE) by the Mediterranean sponge Petrosia ficiformis, how MPs influence key biological process after different times of exposure (24h and 72h) and whether they can be subsequently eliminated. MP uptake increased with time of exposure, with 30.6% of the inoculated MP particles found in sponge samples after 72h. MPs impaired filtration and respiration rates and these effects were still evident 72h after sponges had been transferred in uncontaminated water. Our study shows that time of exposure represents a key factor in determining MP toxicity in sponges. In addition, our results suggest that sponges are able to incorporate foreign particles and may thus be a potential bioindicator for MP pollutants.

The phylum Porifera and their symbionts produce a wide variety of bioactive compounds, playing a central role in their ecology and evolution. In this study, four different extracts (obtained by non-polar and semi-polar extraction methodologies) from the Mediterranean sponge Ircinia oros were tested for their potential antifouling purposes. The evaluation was performed using three different target species, associated with three different endpoints: the marine bacterium Aliivibrio fischeri (inhibition of bioluminescence), the marine diatom Phaeodactylum tricornutum (inhibition of growth) and different development stages of the brackish-water serpulid Ficopomatus enigmaticus (gametes: sperm motion, vitality inhibition and cellular damage; larvae: development; adults: AChE (acetylcholinesterase)-inhibitory activity). Effects of extracts were species-specific and did not vary among different extraction methodologies. In particular, no significant reduction of bioluminescence of A. fischeri was observed for all tested samples. By contrast, extracts inhibited P. tricornutum growth and had toxic effects on different F. enigmaticus’ developmental stages. Obtained results suggest that the proposed test battery can be considered a suitable tool as bioactivity screening of marine natural products.

Anthropogenic stressors can alter the structure and functioning of infaunal communities, which are key drivers of the carbon cycle in marine soft sediments. Nonetheless, the compounded effects of anthropogenic stressors on carbon fluxes in soft benthic systems remain largely unknown. Here, we investigated the cumulative effects of ocean acidification (OA) and hypoxia on the organic carbon fate in marine sediments, through a mesocosm experiment. Isotopically labelled macroalgal detritus (13 C) was used as a tracer to assess carbon incorporation in faunal tissue and in sediments under different experimental conditions. In addition, labelled macroalgae (13 C), previously exposed to elevated CO2 , were also used to assess the organic carbon uptake by fauna and sediments, when both sources and consumers were exposed to elevated CO2 . At elevated CO2 , infauna increased the uptake of carbon, likely as compensatory response to the higher energetic costs faced under adverse environmental conditions. By contrast, there was no increase in carbon uptake by fauna exposed to both stressors in combination, indicating that even a short-term hypoxic event may weaken the ability of marine invertebrates to withstand elevated CO2 conditions. In addition, both hypoxia and elevated CO2 increased organic carbon burial in the sediment, potentially affecting sediment biogeochemical processes. Since hypoxia and OA are predicted to increase in the face of climate change, our results suggest that local reduction of hypoxic events may mitigate the impacts of global climate change on marine soft-sediment systems.

The interaction between top-down and bottom-up forces determines the recovery trajectory of macroalgal forests exposed to multiple stressors. In an oligotrophic system, we experimentally investigated how nutrient inputs affected the recovery of Cystoseira brachycarpa following physical disturbance of varying intensities, both inside forested areas and at the boundary with sea urchin barrens. Unexpectedly, Cystoseira forests were highly resilient to disturbance, as they were able to recover from any partial damage. In general, the addition of nutrients sped up the recovery of Cystoseira. Thus, only the total canopy removal, in combination with either low nutrient availability or intense grazing pressure, promoted the expansion of mat-forming algae or urchin barrens, respectively. Our study suggests that the effects of enhanced nutrient levels may vary according to the trophic characteristics of the waterbody, and hence, are likely to vary among regions of the Mediterranean basin.

A better understanding of species and population responses to thermal stress is critical to predict changes in their distribution under warming scenarios. Seagrasses are a unique group of marine plants that play fundamental roles in marine environments and provide vital ecosystem services. Nevertheless, previous studies on seagrass thermal tolerance have focused exclusively on a handful of species, with the majority of these remaining virtually unexplored. Moreover, to date, no study has compared the response to thermal stress between northern and southern hemisphere seagrasses. Here, we conducted comparative mesocosm experiments using four seagrass species from the northern (i.e. Mediterranean: Posidonia oceanica, Cymodocea nodosa) and southern (i.e. Australia: Posidonia australis and Zostera muelleri) hemisphere as representative of two different life strategies, i.e. climax (P. oceanica, P. australis) and pioneer (C. nodosa, Z. muelleri). Plants acclimatized to the mesocosm conditions at ambient temperature (i.e. 26 °C) during a 5-week period, were exposed to a simulated marine heatwave (i.e. 32 °C) for 2 weeks. Measurements of plant responses, including photo-physiology, morphology, and pigment content, were performed at the end of the warming exposure. Results showed that warming had no significant effects on photosynthetic performances of northern hemisphere seagrasses while negatively impacted their southern hemisphere counterparts. Similarly, warming favored the growth of northern hemisphere plants, but strongly inhibited the development of southern hemisphere species. Furthermore, photo-physiological and pigment content results suggested pioneer seagrasses better dealt with warming than climax species. Our study provides more insights into the field of seagrass ecology and yields potential implication for future seagrass conservation and restoration activities.

18 pages, 5 figures, supplementary data https://doi.org/10.1016/j.biocon.2021.109175.-- The data supporting the findings of this study are available in the Supplementary Materials (Appendix 3–5, Table A3-A5). Raw datasets (where available) and results summary tables for each analysis of human mobility and empirical datasets are deposited in a github repository: https://github.com/rjcommand/PAN-Environment, The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness, The Canada Research Chairs program provided funding for the core writing team. Field research funding was provided by A.G. Leventis Foundation; Agence Nationale de la Recherche, [grant number ANR-18-32–0010CE-01 (JCJC PEPPER)]; Agencia Estatal de Investigaci; Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação (ARDITI), [grant number M1420-09-5369-FSE-000002]; Alan Peterson; ArcticNet; Arkadaşlar; Army Corp of Engineers; Artificial Reef Program; Australia's Integrated Marine Observing System (IMOS), National Collaborative; Research Infrastructure Strategy (NCRIS), University of Tasmania; Australian Institute of Marine Science; Australian Research Council, [grant number LP140100222]; Bai Xian Asia Institute; Batubay Özkan; BC Hydro Fish and Wildlife Compensation Program; Ben-Gurion University of the Negev; Bertarelli Foundation; Bertarelli Programme in Marine Science; Bilge Bahar; Bill and Melinda Gates Foundation; Biology Society of South Australia; Boston University; Burak Över; California State Assembly member Patrick O'Donnell; California State University Council on Ocean Affairs, Science & Technology; California State University Long Beach; Canada Foundation for Innovation (Major Science Initiative Fund and funding to Oceans Network Canada), [grant number MSI 30199 for ONC]; Cape Eleuthera Foundation; Centre National d'Etudes Spatiales; Centre National de la Recherche Scientifique; Charles Darwin Foundation, [grant number 2398]; Colombian Institute for the Development of Science and Technology (COLCIENCIAS), [grant number 811–2018]; Colombian Ministry of Environment and Sustainable Development, [grant number 0041–2020]; Columbia Basin Trust; Commission for Environmental Cooperation; Cornell Lab of Ornithology; Cultural practices and environmental certification of beaches, Universidad de la Costa, Colombia, [grant number INV.1106–01–002-15, 2020–21]; Department of Conservation New Zealand; Direction de l'Environnement de Polynésie Française; Disney Conservation Fund; DSI-NRF Centre of; Excellence at the FitzPatrick Institute of African Ornithology; Ecology Project International; Emin Özgür; Environment and Climate Change Canada; European Community: RTD programme - Species Support to Policies; European Community's Seventh Framework Programme; European Union; European Union's Horizon 2020 research and innovation programme, Marie Skłodowska-Curie, [grant number 798091, 794938]; Faruk Eczacıbaşı; Faruk Yalçın Zoo; Field research funding was provided by King Abdullah University of Science and Technology; Fish and Wildlife Compensation Program; Fisheries and Oceans Canada; Florida Fish and Wildlife Conservation Commission, [grant numbers FWC-12164, FWC-14026, FWC-19050]; Fondo Europeo de Desarrollo Regional; Fonds québécois de la recherche nature et technologies; Foundation Segré; Fundação para a Ciência e a Tecnologia (FCT Portugal); Galapagos National Park Directorate research, [grant number PC-41-20]; Gordon and Betty Moore Foundation, [grant number GBMF9881 and GBMF 8072]; Government of Tristan da Cunha; Habitat; Conservation Trust Foundation; Holsworth Wildlife Research Endowment; Institute of Biology of the Southern Seas, Sevastopol, Russia; Instituto de Investigación de Recursos Biológicos Alexander von Humboldt; Instituto Nacional de Pesquisas Espaciais (INPE), Brazil; Israeli Academy of Science's Adams Fellowship; King Family Trust; Labex, CORAIL, France; Liber Ero Fellowship; LIFE (European Union), [grant number LIFE16 NAT/BG/000874]; María de Maeztu Program for Units of Excellence in R&D; Ministry of Science and Innovation, FEDER, SPASIMM,; Spain, [grant number FIS2016–80067-P (AEI/FEDER, UE)]; MOE-Korea, [grant number 2020002990006]; Mohamed bin Zayed Species Conservation Fund; Montreal Space for Life; National Aeronautics and Space Administration (NASA) Earth and Space Science Fellowship Program; National Geographic Society, [grant numbers NGS-82515R-20]; National Natural Science Fund of China; National Oceanic and Atmospheric Administration; National Parks Board, Singapore; National Science and Technology Major Project of China; National Science Foundation, [grant number DEB-1832016]; Natural Environment Research Council of the UK; Natural Sciences and Engineering Research Council of Canada (NSERC), Alliance COVID-19 grant program, [grant numbers ALLRP 550721–20, RGPIN-2014-06229 (year: 2014), RGPIN-2016-05772 (year: 2016)]; Neiser Foundation; Nekton Foundation; Network of Centre of Excellence of Canada: ArcticNet; North Family Foundation; Ocean Tracking Network; Ömer Külahçıoğlu; Oregon State University; Parks Canada Agency (Lake Louise, Yoho, and Kootenay Field Unit); Pew Charitable Trusts; Porsim Kanaf partnership; President's International Fellowship Initiative for postdoctoral researchers Chinese Academy of Sciences, [grant number 2019 PB0143]; Red Sea Research Center; Regional Government of the Azores, [grant number M3.1a/F/025/2015]; Regione Toscana; Rotary Club of Rhinebeck; Save our Seas Foundation; Science & Technology (CSU COAST); Science City Davos, Naturforschende Gesellschaft Davos; Seha İşmen; Sentinelle Nord program from the Canada First Research Excellence Fund; Servizio Foreste e Fauna (Provincia Autonoma di Trento); Sigrid Rausing Trust; Simon Fraser University; Sitka Foundation; Sivil Toplum Geliştirme Merkezi Derneği; South African National Parks (SANParks); South Australian Department for Environment and Water; Southern California Tuna Club (SCTC); Spanish Ministry for the Ecological Transition and the Demographic Challenge; Spanish Ministry of Economy and Competitiveness; Spanish Ministry of Science and Innovation; State of California; Sternlicht Family Foundation; Suna Reyent; Sunshine Coast Regional Council; Tarea Vida, CEMZOC, Universidad de Oriente, Cuba, [grant number 10523, 2020]; Teck Coal; The Hamilton Waterfront Trust; The Ian Potter Foundation, Coastwest, Western Australian State NRM; The Red Sea Development Company; The Wanderlust Fund; The Whitley Fund; Trans-Anatolian Natural Gas Pipeline; Tula Foundation (Hakai Institute); University of Arizona; University of Pisa; US Fish and Wildlife Service; US Geological Survey; Valencian Regional Government; Vermont Center for Ecostudies; Victorian Fisheries Authority; VMRC Fishing License Fund; and Wildlife Warriors Worldwide, With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S

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 modifying 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 projection on what could be the future of this essential component of Mediterranean marine ecosystems.

Microplastic pollution is increasingly recognized as a prominent threat to marine life. Understanding the role of bioturbators is crucial to determine to what extent marine sediments can act as a microplastic sink. The presence of microplastics has been documented in holothurians, but no study has investigated how the ingestion-egestion process influences their bioavailability. Using the Mediterranean deposit-feeder, Holothuria tubulosa, as a model system, we assessed if, upon ingestion, plastic particles are accumulated in pseudofeces and if the passage through the digestive tract reduces their size. To this end, the number, shape and colour of plastic particles was compared between pseudofeces and surrounding surficial sediments collected along the edges of a seagrass meadow. Pseudofeces were enriched in plastic fragments with respect to surficial sediments, suggesting a selective ingestion of fragments over fibres. By contrast, there was no difference in the size or colour of plastic particles between pseudofeces and sediments. In addition, by means of a laboratory experiment, we evaluated how microplastic resuspension rates from pseudofeces compares with those from surficial sediments. Under standard water movement conditions, the resuspension of labelled microplastics from pseudofeces was much greater than that from sediments (i.e., about 92% and 26% at the end of the experimental trial). Greater relative abundance of fine material (i.e., pelite) in pseudofeces than sediments could explain their physical instability and, hence, their lower microplastic retention. Our results suggest that pseudofeces of H. tubulosa not only represent a hotspot for plastic fragment concentration, but, due to their surficial deposition and rapid dissolution, they could also promote their transfer to the water column. Ingestion and egestion of microplastics by this sea cucumber, although not altering their size, may thus enhance their bioavailability.

The progressive expansion of human activities is causing unprecedented changes to marine ecosystems. In some cases, the extent of these changes may be so large as to generate ecosystems in which structure and functioning have no historical analogs (i.e. novel ecosystems). Here, we review the main abiotic and biotic drivers of change in the marine realm and provide a critical assessment of ecosystems for which there is empirical evidence of human-induced shifts into novel states. Our review indicates that there is evidence for human agency of changes, no-analog species composition and threshold crossing for a variety of marine ecosystems, including intertidal rocky shores, temperate and tropical reefs, estuaries and pelagic systems, while there is no definitive proof of irreversibility of changes. We discuss how a more thorough recognition of the novel ecosystem concept may help initiate conservation and restoration efforts in each of these systems.

Nutrient enrichment is a major threat to subtidal macroalgal forests. Several studies have shown that nutrient inputs can enhance the ability of opportunistic algal species to acquire space freed by disturbance, at the expense of architecturally complex species that form forests. However, competition between canopy- and turf-forming macroalgae is not limited to the aftermath of disturbance. Canopy-forming macroalgae can provide suitable substratum for diverse epibiont assemblages, including both algae (epiphytes) and sessile invertebrates (epizoans). Despite evidence of enhanced epiphyte loading under eutrophic conditions, few experimental studies have assessed how nutrient enrichment influences the structure of epibiont assemblages on canopy-forming macroalgae at the edge versus inside forests. In oligotrophic waters of the NW Mediterranean, we experimentally tested the hypothesis that nutrient-driven proliferation of opportunistic epiphytic algae would affect the performance of the fucoid, Carpodesmia brachycarpa, and reduce the richness and abundance of the epizoan species they support. We predicted negative effects of nutrient enrichment to be greater at the edge than inside forests and on thalli that had recovered in cleared areas than on those within undisturbed canopy stands. Nutrient enrichment did not affect the photosynthetic efficiency and reproductive output of C. brachycarpa. By contrast, it enhanced herbivore consumption and decreased the cover and diversity of epizoans at forest edges, likely by stimulating the foraging activity of Arbacia lixula, the most abundant sea urchin in adjacent encrusting coralline barrens. Fertilization of areas inside forests had no effect on either C. brachycarpa or epibiont assemblages. Finally, nutrient enrichment effects did not vary between cleared and undisturbed areas. Our results show that moderate nutrient enrichment of oligotrophic waters does not necessarily cause the proliferation of epiphytes and, hence, a strengthening of their competitive effects on canopy-forming macroalgae. Nevertheless, enhanced herbivory damage to fertilized thalli at forest edges suggests that fragmentation could reduce the resilience of macroalgal forests and associated epibiont assemblages to nutrient enrichment.

Este artículo contiene 7 páginas, 3 figuras, 1 tabla., The global distribution of primary production and consumption by humans (fisheries) is well-documented, but we have no map linking the central ecological process of consumption within food webs to temperature and other ecological drivers. Using standardized assays that span 105° of latitude on four continents, we show that rates of bait consumption by generalist predators in shallow marine ecosystems are tightly linked to both temperature and the composition of consumer assemblages. Unexpectedly, rates of consumption peaked at midlatitudes (25 to 35°) in both Northern and Southern Hemispheres across both seagrass and unvegetated sediment habitats. This pattern contrasts with terrestrial systems, where biotic interactions reportedly weaken away from the equator, but it parallels an emerging pattern of a subtropical peak in marine biodiversity. The higher consumption at midlatitudes was closely related to the type of consumers present, which explained rates of consumption better than consumer density, biomass, species diversity, or habitat. Indeed, the apparent effect of temperature on consumption was mostly driven by temperature-associated turnover in consumer community composition. Our findings reinforce the key influence of climate warming on altered species composition and highlight its implications for the functioning of Earth’s ecosystems., We acknowledge funding from the Smithsonian Institution and the Tula Foundation.

Native habitat-forming species can facilitate invasion by reducing environmental stress or consumer pressure. However, the intensity of one stressor along a local gradient may differ when expanding the scale of observation to encompass major variations in background environmental conditions. In this study, we determined how facilitation of the invasive porcelain crab, Petrolisthes elongatus, by the native tube-forming serpulid, Galeolaria caespitosa, varied with environmental gradients at local (tidal height) and larger (wave exposure) spatial scales. G. caespitosa constructs a complex calcareous matrix on the underside of intertidal boulders and we predicted that its positive effects on P. elongatus density would increase in intensity with shore height and be stronger at wave-sheltered than wave-exposed locations. To test these predictions, we conducted two experiments. First, we determined the effects of serpulid presence (boulders with live or dead serpulid matrix vs. bare boulders) at six shore heights that covered the intertidal distribution of P. elongatus. Second, we determined the effects of serpulid presence (present vs. absent), shore height (high vs. low) and wave exposure (sheltered vs. exposed) on crabs across six locations within the invaded range in northern Tasmania, Australia. In Experiment 1, the presence of serpulids (either dead or alive) enhanced P. elongatus densities at all shore heights, with facilitation intensity (as determined by a relative interaction index; RII) tending to increase with shore height. In Experiment 2, serpulids facilitated P. elongatus across shore heights and wave exposures, although crab densities were lower at high shore levels of wave-sheltered locations. However, the intensity of crab facilitation by serpulids was greater on wave-sheltered than on wave-exposed shores, but only at the high shore level. This study demonstrates that local effects of native habitat-formers on invasive species are dependent on prevailing environmental conditions at larger spatial scales and that, under more stressful conditions, invaders become increasingly reliant on positive interactions with native habitat-formers. Increased strength of local-scale facilitation by native species, dampening broader scale variations in environmental stressors, could enhance the ability of invasive species to establish self-sustaining populations in the invaded range.

Climate change and coastal urbanization are driving the replacement of natural habitats with artificial structures and reclaimed land globally. These novel habitats are often poor surrogates for natural habitats. The application of integrated greening of grey infrastructure (IGGI) to artificial shorelines demonstrates how multifunctional structures can provide biodiversity benefits whilst simultaneously serving their primary engineering function. IGGI is being embraced globally, despite many knowledge gaps and limitations. It is a management tool to compensate anthropogenic impacts as part of the Mitigation Hierarchy. There is considerable scope for misuse and ‘greenwashing’ however, by making new developments appear more acceptable, thus facilitating the regulatory process. We encourage researchers to exercise caution when reporting on small-scale experimental trials. We advocate that greater attention is paid to when experiments ‘fail’ or yield unintended outcomes. We advise revisiting, repeating and expanding on experiments to test responses over broader spatio-temporal scales to improve the evidence base. Synthesis and applications. Where societal and economic demand makes development inevitable, particular attention should be paid to avoiding, minimizing and rehabilitating environmental impacts. Integrated greening of grey infrastructure (IGGI) should be implemented as partial compensation for environmental damage. Mutual benefits for both humans and nature can be achieved when IGGI is implemented retrospectively in previously developed or degraded environments. We caution, however, that any promise of net biodiversity gain from new developments should be scrutinized and any local ecological benefits set in the context of the wider environmental impacts. A ‘greened’ development will always impinge on natural systems, a reality that is much less recognized in the sea than on land.

Macroalgal competition can indirectly influence the health of corals and their response to changing environmental conditions by altering their associated bacterial community. However, the effect of macroalgae on the composition of epilithic microbial biofilms, an important determinant of coral recruitment, is poorly known. In the back-reefs of Moorea (French Polynesia), we evaluated how the experimental removal of either the canopy of the seaweed Turbinaria ornata or that of the entire macroalgal assemblage influenced the composition of the bacterial biofilm and coral recruitment on macroalga-free substrata. The number of bacterial colonies on culture plates inoculated with dilutions of 9 d old biofilm from canopy removal sites was smaller compared with control sites. After 3.5 mo, the diversity of bacterial operational taxonomic units (OTUs) was lower at both canopy and total macroalgal removal sites. Total macroalgal removal sites had a lower relative abundance of several bacterial families, including Rhodobacteraceae, Erythrobacteraceae, Cyanobacteria Family IV and Family VIII, Flavobacteriaceae and Verrucomicrobiaceae. After 8 mo, coral recruitment was generally low, but greater at total macroalgal removal sites. The relative abundance of Cyanobacteria, Sphingo - bacteria and Verrucomicrobia was negatively correlated with coral recruitment and explained ~70% of variation in coral recruit density. Our study shows that the removal of T. ornata and understory macroalgae influences the composition of epilithic bacterial assemblages and coral recruitment. Thus, eradication campaigns are unlikely to sustain long-term reductions in the abundance of T. ornata and, hence, increase coral recruitment, when plant holdfasts and understory macroalgae are left in place.

Invasion success is regulated by multiple factors. While the roles of disturbance and propagule pressure in regulating the establishment of non-native species are widely acknowledged, that of propagule morphology (a proxy for quality) is poorly known. By means of a multi-factorial field experiment, we tested how the number (5 vs. 10) and quality (intact, without fronds or without rhizoids) of fragments of the clonal invasive seaweed, Caulerpa cylindracea, influenced its ability to establish in patches of the native seagrass, Posidonia oceanica, exposed to different intensities of disturbance (0, 50, or 100% reduction in canopy cover). We hypothesized that the ability of fragments to establish would be greater for intact fragments (high quality) and reduced more by frond removal (low quality) than rhizoid removal (intermediate quality). At low propagule pressure or quality, fragment establishment was predicted to increase with increasing disturbance, whereas, at high propagule pressure or quality, it was predicted to be high regardless of disturbance intensity. Disturbance intensity, fragment number and quality had independent effects on C. cylindracea establishment success. Disturbance always facilitated fragment establishment. However, fragments retaining fronds, either intact or deprived of rhizoids, had higher establishment success than fragments deprived of fronds. Increasing propagule number had weak effects on the cover of C. cylindracea. Our results demonstrate that propagule traits enabling the acquisition of resources made available by disturbance can be more important than propagule number in determining the establishment and spread of clonal non-native plants. More generally, our study suggests that propagule quality is a key, yet underexplored, determinant of invasion success.

The global decline of canopy-forming macroalgae has stimulated research on the mechanism regulating shifts among alternative habitats on rocky reefs. The effects of sea urchin grazing and alterations of environmental conditions are now acknowledged as the main drivers of shifts between canopy-formers and encrusting coralline barrens and algal turfs, respectively. The conditions under which these mechanisms operate remains, however, somewhat elusive. This is mostly a consequence of the fact that our current understanding has been generated by envisioning habitat shifts as dichotomic, at odds with rocky reef landscapes being composed by mosaics of habitats and with evidence of strong interactions among the species that compose each of the alternative habitats. Using data from a long-term sampling program and path analysis, we investigated how wave-exposure and human-induced degradation of environmental conditions regulate the mechanisms maintaining algal canopies formed by Cystoseira crinita, barren habitats and algal turfs as alternative states on subtidal reefs in the NW Mediterranean. In the Tuscan Archipelago, wave-exposure had positive effects on sea urchins, which, likely due to their low mean density, had weak effects on each of the alternative habitats. Canopy-forming macroalgae resulted, instead, to exert strong negative effects on the abundance of algal turfs. Since data from the Tuscan Archipelago did not explain any of the variation in the abundance of C. crinita canopies, a further analysis was performed including data from the coast of Tuscany to assess the role of cumulative human impacts in regulating habitat shifts. This showed that degradation of environmental conditions is a direct cause of the decline of macroalgal canopies, indirectly favouring the dominance of algal turfs. Our study suggests that management of human impacts should be considered a priority for preserving subtidal canopies formed by Cystoseira in the NW Mediterranean and that conservation efforts based exclusively on the control of sea urchin populations might be doomed to failure in some areas.

Seagrasses are globally declining and often their loss is due to synergies among stressors. We investigated the interactive effects of eutrophication and burial on the Mediterranean seagrass, Posidonia oceanica. A field experiment was conducted to estimate whether shoot survival depends on the interactive effects of three levels of intensity of both stressors and to identify early changes in plants (i.e., morphological, physiological and biochemical, and expression of stress-related genes) that may serve to detect signals of imminent shoot density collapse. Sediment burial and nutrient enrichment produced interactive effects on P. oceanica shoot survival, as high nutrient levels had the potential to accelerate the regression of the seagrass exposed to high burial (HB). After 11 weeks, HB in combination with either high or medium nutrient enrichment caused a shoot loss of about 60%. Changes in morphology were poor predictors of the seagrass decline. Likewise, few biochemical variables were associated with P. oceanica survival (the phenolics, ORAC and leaf δ34S). In contrast, the expression of target genes had the highest correlation with plant survival: photosynthetic genes (ATPa, psbD and psbA) were up-regulated in response to high burial, while carbon metabolism genes (CA-chl, PGK and GADPH) were down-regulated. Therefore, die-offs due to high sedimentation rate in eutrophic areas can only be anticipated by altered expression of stress-related genes that may warn the imminent seagrass collapse. Management of local stressors, such as nutrient pollution, may enhance seagrass resilience in the face of the intensification of extreme climate events, such as floods.

There is increasing evidence that the severity of the ecological impact of non-native species does not necessarily scale linearly with their abundance in the introduced range. Nonetheless, the potential of low abundance invaders to alter the resilience of native communities to disturbance has been poorly explored. On Mediterranean rocky reefs, we tested the hypothesis that (1) a pulse disturbance opening gaps within canopy stands formed by the fucoid seaweed Cystoseira brachycarpa facilitates the establishment of the non-native seaweed Caulerpa cylindracea and that (2), once established, the seaweed can reduce the recovery of macroalgal canopies. In July 2011, C. cylindracea was experimentally transplanted in small and large plots that were either cleared of the canopy or left untouched. After 45 months, the cover of C. cylindracea was greatest in small canopy-removal plots, without, however, achieving values exceeding ~10%. Nonetheless, such a low abundance of C. cylindracea caused a threefold reduction in canopy recovery. The establishment of C. cylindracea in canopy-removal plots did not alter the structure of the understory assemblages or the cover of turf-forming, erect and encrusting algae and sessile invertebrates. Our results suggest that some non-native species may be stronger competitors than natives, despite their low abundance. This property has important implications for control programs since not achieving the total eradication of the targeted invader would make little progress towards the mitigation of its impacts. Finally, our results show that non-native species acting as passengers of change can ultimately promote the persistence of alternative degraded states.

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.