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The blue crab Callinectes sapidus has shown an immense capacity to adapt to new habitats in the Mediterranean Sea. Followingthe numerous reports of its proliferation along western Sicily, an investigation was conducted to identify any existing populations. In August 2021, a population of blue crabs was found in the natural reserve of Trapani which includes a large area of restored saltmarshes. In this study, by developing a tracking system using Unmanned Aerial Vehicles (UAV), we studied (i) the behavior of blue crabs on an hourly scale, and (ii) the weekly position of blue crabs in the saltmarshes to determine substrate preference. This study provides a new approach to better understand C. sapidus’ habitat use and their potential impact on local biodiversity. Blue crab activity was found to increase with temperature and tidal height, with a peak in activity observed at high tide and at maximum temperatures: the mean speed (m h-1) was higher (12.1 ± 8.7 m h-1) at T > 28 °C than at T = 23.7 °C (2.0 ± 3.2 m h-1). Considering habitat use, in 49 ± 13 % of the cases, blue crabs were observed on the sand, while 21 ± 14 % in the Cymodocea meadows, and 30 ± 15 % in the Ruppia meadows. These microhabitats provide a refuge for C. sapidus and should be prioritized and studied before management plans are designed and implemented to manage this important invasive species.

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.

Ecologically dominant species often define ecosystem states, but as human disturbances intensify, their subordinate counterparts increasingly displace them. We consider the duality of disturbance by examining how environmental drivers can simultaneously act as a stressor to dominant species and as a resource to subordinates. Using a model ecosystem, we demonstrate that CO2-driven interactions between species can account for such reversals in dominance; i.e., the displacement of dominants (kelp forests) by subordinates (turf algae). We established that CO2 enrichment had a direct positive effect on productivity of turfs, but a negligible effect on kelp. CO2 enrichment further suppressed the abundance and feeding rate of the primary grazer of turfs (sea urchins), but had an opposite effect on the minor grazer (gastropods). Thus, boosted production of subordinate producers, exacerbated by a net reduction in its consumption by primary grazers, accounts for community change (i.e., turf displacing kelp). Ecosystem collapse, therefore, is more likely when resource enrichment alters competitive dominance of producers, and consumers fail to compensate. By recognizing such duality in the responses of interacting species to disturbance, which may stabilize or exacerbate change, we can begin to understand how intensifying human disturbances determine whether or not ecosystems undergo phase shifts. Refereed/Peer-reviewed

Biodiversity plays a key role for our planet by buffering ongoing and future changes in environmental conditions. We tested if canopy-forming algae enhancing biodiversity (CEB) in a Mediterranean intertidal reef ecological community could alleviate the effect of stressors (heat waves and pollution from sewage) on community metabolic rates (as expressed by oxygen consumption) used as a proxy of community functioning. CEB exerted a buffering effect related to the properties of stressor: physical-pulsing (heat wave) and chronic-trophic (sewage). After a simulated heat wave, CEB was effective in buffering the impacts of detrimental temperatures on the functioning of the community. In reefs exposed to chronic sewage effluents, benefits derived from CEB were less evident, which is likely due to the stressor's contextual action. The results support the hypothesis that ecological responses depend on stressor typology acting at local level and provide insights for improving management measures to mitigate anthropogenic disturbance.

Estimated larval backward trajectories of three Tuna species, namely, Atlantic Bluefin Tuna (Thunnus thynnus, Linnaeus, 1758), Bullet Tuna (Auxis Rochei, Risso, 1801) and Albacore Tuna (Thunnus alalunga, Bonnaterre, 1788) in the central Mediterranean Sea, were used to characterize their spawning habitats, and to assess the impact of changes due to the major environmental parameters (i.e., sea surface temperature and chlorophyll-a concentration) on larval development during their advection by surface currents. We assumed that the environmental variability experienced by larvae along their paths may have influenced their development, also affecting their survival. Our results showed that the Tuna larvae underwent an accelerated growth in favorable environmental conditions, impacting on the notochord development. In addition, further updated information on spawning and larval retention habitats of Atlantic Bluefin Tuna, Bullet and Albacore Tunas in the central Mediterranean Sea were delivered.

Around 350 million tonnes of plastics are annually produced worldwide. A remarkable percentage of these products is dispersed in the environment, finally reaching and dispersed in the marine environment. Recent field surveys detected microplastics’ concentrations in the Mediterranean Sea. The most commonly polymers found were polyethylene, polypropylene and viscose, ethylene vinyl acetate and polystyrene. In general, the in-situ monitoring of microplastic pollution is difficult and time consuming. The main goals of this work were to spectrally characterize the most commonly polymers and to quantify their spectral separability that may allow to determine optimal band combinations for imaging techniques monitoring. The spectral signatures of microplastics have been analysed in laboratory, both in dry condition and on water surface, using a full spectrum spectroradiometer. The theoretical use of operational satellite images for remote sensing monitoring was investigated by quantifying the spectral separability achievable by their sensors. The WorldView-3 sensor appears the most suitable for the monitoring but better average spectral separability are expected using the recently released PRISMA images. This research was preparatory to further outdoor experiments needed to better simulate the real acquisition condition.

Macroalgal forests are one of the most productive and valuable marine ecosystems, but yet strongly exposed to fragmentation and loss. Detailed large-scale information on their distribution is largely lacking, hindering conservation initiatives. In this study, a systematic effort to combine spatial data on Cystoseira C. Agardh canopies (Fucales, Phaeophyta) was carried out to develop a Habitat Suitability Model (HSM) at Mediterranean scale, providing critical tools to improve site prioritization for their management, restoration and protection. A georeferenced database on the occurrence of 20 Cystoseira species was produced collecting all the available information from published and grey literature, web data portals and co-authors personal data. Data were associated to 55 predictor variable layers in the (ASCII) raster format and were used in order to develop the HSM by means of a Random Forest, a very effective Machine Learning technique. Knowledge about the distribution of Cystoseira canopies was available for about the 14% of the Mediterranean coastline. Absence data were available only for the 2% of the basin. Despite these gaps, our HSM showed high accuracy levels in reproducing Cystoseira distribution so that the first continuous maps of the habitat across the entire basin was produced. Misclassification errors mainly occurred in the eastern and southern part of the basin, where large gaps of knowledge emerged. The most relevant drivers were the geomorphological ones, followed by anthropogenic variables proxies of pollution and urbanization. Our model shows the importance of data sharing to combine a large number of spatial and environmental data, allowing to individuate areas with high probability of Cystoseira occurrence as suitable for its presence. This approach encourages the use of this modelling tool for the prediction of Cystoseira distribution and for supporting and planning conservation and management initiatives. The step forward is to refine the spatial information of presence-absence data about Cystoseira canopies and of environmental predictors in order to address species-specific assessments.

The green lipped mussel, Perna viridis, is an important aquaculture species throughout the Indo-Pacific region where production is often impacted by environmental degradation. To predict the impacts and mitigate against environmental problems due to various kinds of anthropogenic pollution, such as heavy metals and eutrophication, on P. viridis aquaculture a Dynamic Energy Budget (DEB) model was constructed. By integrating species-specific parameters and regional-specific environmental data the DEB model determined how the life history traits of P. viridis respond to changing environmental conditions. Using various levels of basal maintenance costs and food availability to elucidate the energetic costs due to environmental pollution, the DEB model predicted that a 20% increase in basal maintenance cost due to environmental pollution such as heavy metals will result in a subsequent decrease in both lifetime reproductive output and ultimate body size of P. viridis by ~18% and ~8%, respectively. Increasing food availability can, however, mitigate the energetic constraints due to increased basal maintenance cost. The time to reach commercial size, for example, will be longer by 13% and 3% under lower and higher food availability conditions, respectively when there is a 20% increase in maintenance cost due to environmentally induced stress, which would significantly increase the operational cost of an aquaculture facility. In light of the increased importance of P. viridis as an aquaculture species, the P. viridis DEB model can, therefore, be used to illustrate the effects of varying environmental conditions on P. viridis life history traits which are relevant to the success of aquaculture facilities, and contribute towards better management of this species.

Fisheries currently represent the main source of animal protein intake worldwide, although catches of most commercial species are at or beyond maximum sustainable yields. Increasing production would require an excess of exploitation levels and aquaculture is expected to become crucial in sustaining a growing seafood demand. Nonetheless, many threats are expected to affect aquaculture and the increased production must evolve in a way that minimizes environmental and socio-economic impacts. The claimed sustainable development of human activities at sea (blue growth and economy) seeks for new joint analyses and solutions at (trans-)national systemic level should be planned and applied. To meet a sustainable development, both production and management approaches should evolve. Here we propose a conceptual framework to integrate a “downscaling approach” based on functional features of cultivated organisms to accommodate multiple stressors in setting sustainable development standards to design adaptive solutions fitting with the management of marine space.

Connecting the nonlinear and often counterintuitive physiological effects of multiple environmental drivers to the emergent impacts on ecosystems is a fundamental challenge. Unfortunately, the disconnect between the way “stressors” (e.g., warming) is considered in organismal (physiological) and ecological (community) contexts continues to hamper progress. Environmental drivers typically elicit biphasic physiological responses, where performance declines at levels above and below some optimum. It is also well understood that species exhibit highly variable response surfaces to these changes so that the optimum level of any environmental driver can vary among interacting species. Thus, species interactions are unlikely to go unaltered under environmental change. However, while these nonlinear, species-specific physiological relationships between environment and performance appear to be general, rarely are they incorporated into predictions of ecological tipping points. Instead, most ecosystem-level studies focus on varying levels of “stress” and frequently assume that any deviation from “normal” environmental conditions has similar effects, albeit with different magnitudes, on all of the species within a community. We consider a framework that realigns the positive and negative physiological effects of changes in climatic and nonclimatic drivers with indirect ecological responses. Using a series of simple models based on direct physiological responses to temperature and ocean pCO2, we explore how variation in environment-performance relationships among primary producers and consumers translates into community-level effects via trophic interactions. These models show that even in the absence of direct mortality, mismatched responses resulting from often subtle changes in the physical environment can lead to substantial ecosystem-level change. Refereed/Peer-reviewed