ß-diversity reveals ecological connectivity patterns underlying marine community recovery: Implications for conservation.

As ß-diversity can be seen as a proxy of ecological connections among species assemblages, modeling the decay of similarity in species composition at increasing distance may help elucidate spatial patterns of connectivity and local- to large-scale processes driving community assembly within a marine region. This, in turn, may provide invaluable information for setting ecologically coherent networks of marine protected areas (MPAs) in which protected communities are potentially interrelated and can mutually sustain against environmental perturbations. However, field studies investigating changes in ß-diversity patterns at a range of spatial scales and in relation to disturbance are scant, limiting our understanding of how spatial ecological connections among marine communities may affect their recovery dynamics. We carried out a manipulative experiment simulating a strong physical disturbance on subtidal rocky reefs at several locations spanning >1000 km of coast in the Adriatic Sea (Mediterranean Sea) and compared ß-diversity patterns and decay of similarity with distance and time by current transport between undisturbed and experimentally disturbed macrobenthic assemblages to shed light on connectivity processes and scales involved in recovery. In contrast to the expectation that very local-scale processes, such as vegetative regrowth and larval supply from neighboring undisturbed assemblages, might be the major determinants of recovery in disturbed patches, we found that connectivity mediated by currents at larger spatial scales strongly contributed to shape community reassembly after disturbance. Across our study sites in the Adriatic Sea, ß-diversity patterns suggested that additional protected sites that matched hotspots of propagule exchange could increase the complementarity and strengthen the ecological connectivity throughout the MPA network. More generally, conditional to habitat distribution and selection of sites of high conservation priority (e.g., biodiversity hotspots), setting network internode distance within 100-150 km, along with sizing no-take zones to cover at least 5 km of coast, would help enhance the potential connectivity of Mediterranean subtidal rocky reef assemblages from local to large scale. These results can help improve conservation planning to achieve the goals of promoting ecological connectivity within MPA networks and enhancing their effectiveness in protecting marine communities against rapidly increasing natural and anthropogenic disturbances.

Mediterranean rocky reefs in the Anthropocene: Present status and future concerns.

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.

A review of the combined effects of climate change and other local human stressors on the marine environment.

Climate change (CC) is a key, global driver of change of marine ecosystems. At local and regional scales, other local human stressors (LS) can interact with CC and modify its effects on marine ecosystems. Understanding the response of the marine environment to the combined effects of CC and LS is crucial to inform marine ecosystem-based management and planning, yet our knowledge of the potential effects of such interactions is fragmented. At a global scale, we explored how cumulative effect assessments (CEAs) have addressed CC in the marine realm and discuss progress and shortcomings of current approaches. For this we conducted a systematic review on how CEAs investigated at different levels of biological organization ecological responses, functional aspects, and the combined effect of CC and HS. Globally, the effects of 52 LS and of 27 CC-related stressors on the marine environment have been studied in combination, such as industrial fisheries with change in temperature, or sea level rise with artisanal fisheries, marine litter, change in sediment load and introduced alien species. CC generally intensified the effects of LS at species level. At trophic groups and ecosystem levels, the effects of CC either intensified or mitigated the effects of other HS depending on the trophic groups or the environmental conditions involved, thus suggesting that the combined effects of CC and LS are context-dependent and vary among and within ecosystems. Our results highlight that large-scale assessments on the spatial interaction and combined effects of CC and LS remain limited. More importantly, our results strengthen the urgent need of CEAs to capture local-scale effects of stressors that can exacerbate climate-induced changes. Ultimately, this will allow identifying management measures that aid counteracting CC effects at relevant scales.

Are we ready for scaling up restoration actions? An insight from Mediterranean macroalgal canopies.

Extensive loss of macroalgal forests advocates for large-scale restoration interventions, to compensate habitat degradation and recover the associated ecological functions and services. Yet, restoration attempts have generally been limited to small spatial extensions, with the principal aim of developing efficient restoration techniques. Here, the success of outplanting Cystoseira amentacea v. stricta germlings cultured in aquaria was experimentally explored at a scale of tens of kms, by means of a multifactorial experimental design. In the intertidal rocky shores of SE Italy, locations with a continuous distribution for hundreds of meters or with few thalli forming patches of few centimeters of C. amentacea canopy were selected. In each location, the effects of adult conspecifics and the exclusion of macrograzers (salema fish and sea urchins) on the survival of germlings were tested. We evaluated the most critical determinants of mortality for germlings, including the overlooked pressure of mesograzers (e.g. amphipods, small mollusks, polychaetes). Despite the high mortality observed during outplanting and early settlement stages, survival of C. amentacea germlings was consistently favored by the exclusion of macrograzers, while the presence of adult conspecifics had no effects. In addition, the cost analysis of the interventions showed the feasibility of the ex-situ method, representing an essential tool for preserving Cystoseira forests. Large scale restoration is possible but requires baseline information with an in-depth knowledge of the species ecology and of the areas to be restored, together with the development of specific cultivation protocols to make consistently efficient restoration interventions.

Effects of a glyphosate-based herbicide on Fucus virsoides (Fucales, Ochrophyta) photosynthetic efficiency.

Herbicides are increasingly recognised as sources of water pollution. Glyphosate-based herbicides (GBHs) are widely used because of their low cost and high effectiveness. By measuring the photosynthetic efficiency of Fucus virsoides fronds exposed to a GBH (Roundup® Power 2.0), we investigated the effect of a continuous exposure (6 days) and the potential of recovery after a short exposure (24 h). Both experiments were carried out combining GBH with and without nutrient enrichment, simulating a runoff event. A factorial experimental design allowed us to assess the potential of interactions between GBH and nutrients, which are likely to co-occur in coastal areas. Our results show deleterious effects of GBH at low concentration on F. virsoides, independently from the duration of exposure and the presence of nutrients.

Mediterranean Bioconstructions Along the Italian Coast.

Marine bioconstructions are biodiversity-rich, three-dimensional biogenic structures, regulating key ecological functions of benthic ecosystems worldwide. Tropical coral reefs are outstanding for their beauty, diversity and complexity, but analogous types of bioconstructions are also present in temperate seas. The main bioconstructions in the Mediterranean Sea are represented by coralligenous formations, vermetid reefs, deep-sea cold-water corals, Lithophyllum byssoides trottoirs, coral banks formed by the shallow-water corals Cladocora caespitosa or Astroides calycularis, and sabellariid or serpulid worm reefs. Bioconstructions change the morphological and chemicophysical features of primary substrates and create new habitats for a large variety of organisms, playing pivotal roles in ecosystem functioning. In spite of their importance, Mediterranean bioconstructions have not received the same attention that tropical coral reefs have, and the knowledge of their biology, ecology and distribution is still fragmentary. All existing data about the spatial distribution of Italian bioconstructions have been collected, together with information about their growth patterns, dynamics and connectivity. The degradation of these habitats as a consequence of anthropogenic pressures (pollution, organic enrichment, fishery, coastal development, direct physical disturbance), climate change and the spread of invasive species was also investigated. The study of bioconstructions requires a holistic approach leading to a better understanding of their ecology and the application of more insightful management and conservation measures at basin scale, within ecologically coherent units based on connectivity: the cells of ecosystem functioning.

Population genomics meet Lagrangian simulations: Oceanographic patterns and long larval duration ensure connectivity among Paracentrotus lividus populations in the Adriatic and Ionian seas.

Connectivity between populations influences both their dynamics and the genetic structuring of species. In this study, we explored connectivity patterns of a marine species with long-distance dispersal, the edible common sea urchin Paracentrotus lividus, focusing mainly on the Adriatic-Ionian basins (Central Mediterranean). We applied a multidisciplinary approach integrating population genomics, based on 1,122 single nucleotide polymorphisms (SNPs) obtained from 2b-RAD in 275 samples, with Lagrangian simulations performed with a biophysical model of larval dispersal. We detected genetic homogeneity among eight population samples collected in the focal Adriatic-Ionian area, whereas weak but significant differentiation was found with respect to two samples from the Western Mediterranean (France and Tunisia). This result was not affected by the few putative outlier loci identified in our dataset. Lagrangian simulations found a significant potential for larval exchange among the eight Adriatic-Ionian locations, supporting the hypothesis of connectivity of P. lividus populations in this area. A peculiar pattern emerged from the comparison of our results with those obtained from published P. lividus cytochrome b (cytb) sequences, the latter revealing genetic differentiation in the same geographic area despite a smaller sample size and a lower power to detect differences. The comparison with studies conducted using nuclear markers on other species with similar pelagic larval durations in the same Adriatic-Ionian locations indicates species-specific differences in genetic connectivity patterns and warns against generalizing single-species results to the entire community of rocky shore habitats.

The Challenge of Planning Conservation Strategies in Threatened Seascapes: Understanding the Role of Fine Scale Assessments of Community Response to Cumulative Human Pressures.

Assessing the distribution and intensity of human threats to biodiversity is a prerequisite for effective spatial planning, harmonizing conservation purposes with sustainable development. In the Mediterranean Sea, the management of Marine Protected Areas (MPAs) is rarely based on explicit consideration of the distribution of multiple stressors, with direct assessment of their effects on ecosystems. This gap limits the effectiveness of protection and is conducive to conflicts among stakeholders. Here, a fine scale assessment of the potential effects of different combinations of stressors (both land- and marine-based) on vulnerable rocky habitats (i.e. lower midlittoral and shallow infralittoral) along 40 km of coast in the western Mediterranean (Ionian Sea) has been carried out. The study area is a paradigmatic example of socio-ecological interactions, where several human uses and conservation measures collide. Significant differences in the structure of assemblages according to different combinations of threats were observed, indicating distinct responses of marine habitats to different sets of human pressures. A more complex three-dimensional structure, higher taxon richness and ß-diversity characterized assemblages subject to low versus high levels of human pressure, consistently across habitats. In addition, the main drivers of change were: closeness to the harbour, water quality, and the relative extension of beaches. Our findings suggest that, although efforts to assess cumulative impacts at large scale may help in individuating priority areas for conservation purposes, the fact that such evaluations are often based on expert opinions and not on actual studies limits their ability to represent real environmental conditions at local scale. Systematic evaluations of local scale effects of anthropogenic drivers of change on biological communities should complement broad scale management strategies to achieve effective sustainability of human exploitation of marine resources.

Grazer removal and nutrient enrichment as recovery enhancers for overexploited rocky subtidal habitats.

Increasing anthropogenic pressures are causing long-lasting regime shifts from high-diversity ecosystems to low-diversity degraded ones. Understanding the effects of multiple threats on ecosystems, and identifying processes allowing for the recovery of biodiversity, are the current major challenges in ecology. In several temperate marine areas, large parts of rocky subtidal habitats characterised by high diversity have been completely degraded to barren grounds by overfishing, including illegal date mussel fishing. Bare areas are characterized by the dominance of sea urchins whose grazing perpetuates the impact of overfishing. We investigated experimentally the separate and combined effects of nutrient enrichment and sea urchin exclusion on the recovery of barren grounds. Our results indicate that the two factors have a synergistic effect leading to the re-establishment of erect macroalgal canopies, enhancing the structural complexity of subtidal assemblages. In particular, in the overfished system considered here, the recovery of disturbed assemblages could occur only if sea urchins are removed. However, the recolonization of barren grounds by erect macroalgae is further enhanced under enriched conditions. This study demonstrates that the recovery of dramatically depleted marine habitats is possible, and provides useful indications for specific management actions, which at present are totally lacking, to achieve the restoration of barren grounds caused by human activity.

Protection enhances community and habitat stability: evidence from a mediterranean marine protected area.

Rare evidences support that Marine Protected Areas (MPAs) enhance the stability of marine habitats and assemblages. Based on nine years of observation (2001-2009) inside and outside a well managed MPA, we assessed the potential of conservation and management actions to modify patterns of spatial and/or temporal variability of Posidonia oceanica meadows, the lower midlittoral and the shallow infralittoral rock assemblages. Significant differences in both temporal variations and spatial patterns were observed between protected and unprotected locations. A lower temporal variability in the protected vs. unprotected assemblages was found in the shallow infralittoral, demonstrating that, at least at local scale, protection can enhance community stability. Macrobenthos with long-lived and relatively slow-growing invertebrates and structurally complex algal forms were homogeneously distributed in space and went through little fluctuations in time. In contrast, a mosaic of disturbed patches featured unprotected locations, with small-scale shifts from macroalgal stands to barrens, and harsh temporal variations between the two states. Opposite patterns of spatial and temporal variability were found for the midlittoral assemblages. Despite an overall clear pattern of seagrass regression through time, protected meadows showed a significantly higher shoot density than unprotected ones, suggesting a higher resistance to local human activities. Our results support the assumption that the exclusion/management of human activities within MPAs enhance the stability of the structural components of protected marine systems, reverting or arresting threat-induced trajectories of change.

Local vs regional effects of substratum on early colonization stages of sessile assemblages.

Substratum type and topographic complexity influence the settlement and persistence of benthic organisms. However, the combined effect of these two factors in affecting colonization patterns at different scales has rarely been investigated. A manipulative experiment was conducted to test the interplay of rock type and roughness in affecting the pattern of subtidal assemblages and to provide tests for the generality of effects across a range of spatial scales (centimetres to hundreds of metres). Replicate tiles of four different rock types, with two levels of surface roughness were deployed in rocky subtidal habitats (5 m depth) at two sites (separated by hundreds of metres) at each of three locations (separated by tens of kilometres). Spatial and temporal variation in the colonization patterns over 9 months differed among rock types. However, large-scale processes appeared to be far more important than substratum type or roughness in determining assemblage structure. Predicting the consequences of the introduction of artificial structures into the coastal marine environment is critical as increasingly parts of coastlines are being modified within the Mediterranean and other regions. The results suggest that further investment is needed to manage and mitigate the effects of the deployment of artificial structures in coastal areas.

Effects of offshore platforms on soft-bottom macro-benthic assemblages: a case study in a Mediterranean gas field.

The exploitation of fossil fuels in the Mediterranean Sea will likely lead to an increase in the number of offshore platforms, a recognized threat for marine biodiversity. To date, in this basin, few attempts have been made to assess the impact of offshore gas and oil platforms on the biodiversity of benthic assemblages. Here, we adopted a structured experimental design coupled with high taxonomic resolution to outline putative effects of gas platforms on soft-bottom macrofauna assemblages in the North Ionian Sea. The analysis was based on a total of 20,295 specimens of 405 taxa, almost entirely identified at species level. Multivariate and univariate analyses showed idiosyncratic patterns of assemblage change with increasing distance from the platforms. Potential reasons underlying such inconsistency are analyzed and the view that structured experimental monitoring is a crucial tool to quantify the extent and magnitude of potential threats and to provide sound baseline information on biodiversity patterns is supported.

Conservation of Mediterranean seascapes: analyses of existing protection schemes.

Marine protected areas (MPAs) are aimed at managing and protecting marine environments. Their design, however, often disregards both a thorough knowledge of the distribution of habitats and assemblages and the use of proper experimental evaluations of the efficacy of MPAs by comparing protected vs. unprotected zones. About 200 MPAs have been recently instituted in the Mediterranean area, but the evidence of their efficacy is scant. The MPA of Torre Guaceto (Southern Adriatic Sea, Italy) is one of the rare cases of effective protection enforcement. The reserve was instituted more than 10 years ago, a period currently considered as sufficient to show responses by organisms to protection. The MPA is divided into a C zone, the general reserve, where many activities are permitted, a B zone, the partial reserve where restrictions increase and two A zones, the integral reserve where access is prohibited. The goals of the paper were to map the distribution of benthic assemblages to assess if they were properly represented in the differently protected zones, and to test the efficacy of protection by quantifying possible differences between the assemblages in two control areas and in the two A zones, where human impact is completely excluded. The analysis of habitat and assemblage distribution within the MPA showed that the zones with total protection do not include most valuable environmental types. Most of the considered variables (i.e. cover of substratum, number of taxa, and average abundance of the most common taxa) were not significantly different in and out of the A zones, at each time of sampling. Results, however, suggested a possible effect of protection in modifying patterns of abundance of sponges under Cystoseira canopy (more abundant in the fully protected zone). In the subtidal habitat, differences were found in the structure of the whole assemblage and in the abundance of encrusting coralline red algae (more abundant outside the fully protected area). Notwithstanding the correct general methodology employed in the study, a lack of statistical power could have a role in preventing the detection of ecologically relevant effects of protection. In some instances, data pooling allowed a discrimination between cases where there was clearly no effect of protection and cases where there might be. On this basis, the optimization of this experimental design should be considered in further studies. In any case, if the goals of MPAs have not been clearly stated, efficacy of protection might prove very difficult to test even with the use of sound experimental designs.