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The sea star Hymenodiscus coronata is the only Mediterranean representative of the deep-sea order Brisingida. In the North-eastern Atlantic Ocean, this species is known to create dense aggregations, while, in the Mediterranean basin, it is generally reported as scattered individuals. Through the analysis of the video footage obtained from an extensive ROV campaign carried out in the northern Strait of Sicily in 2021, over 2850 specimens were counted. The specimens, observed between 310 m and 714 m depth, showed a large variability in size and number of arms. It was noted that 17% of the specimens displayed the peculiar "sail position", with all the arms extended vertically in the water column, possibly increasing the filtration rate. Almost the totality of the individuals was noted on soft bottoms, in accordance with the ecological preferences of the species. The density of H. coronata in each site varied between 0.01 and 0.81 individuals m−2, with the highest densities reported in sites characterized by large muddy areas among rocky outcrops and turbulent hydrodynamic conditions. Although the trawling areas exploited in 2021 did not seem to interfere with the presence of H. coronata in the study area, a precautionary approach should be assumed to protect the largest ever reported Mediterranean aggregation of this poorly known species. [ABSTRACT FROM AUTHOR]

Cold-water corals (CWCs) are bioengineering species that can increase habitat heterogeneity and improve the deep sea’s biological diversity and ecosystem functioning. Knowledge of their distribution provides a critical baseline for assessing the effect of natural and anthropogenic impacts on these important deep-sea habitats. The aims of this study are: i) provide new data on the spatial distribution of six CWCs species in the Strait of Sicily, ii) describe the principal environmental and anthropogenic variables that play a role in shaping their distribution, iii) identify hotspots in which individuals belonging to the various species co-occur. Presence-only data of six CWCs species, ten environmental variables (depth, slope, rugosity, aspect, flowdir, temperature, salinity, north bottom current, east bottom current, chlorophyll-a), and one variable relating to bottom trawling effort (Automatic Information System – AIS) were used to predict the suitable habitats. We used Maximum Entropy modelling (MaxEnt) approach and used the AUC (area under the receiver operating characteristic curve) and TSS (true skill statistics) to evaluate the model performance. The results showed excellent AUC, TSS and AUC’s standard deviation mean values for all six species. The validation show high predictive performance. MaxEnt identified slope, depth, and rugosity as the most important predictors, showing the highest percentage contribution for all six species considered. Throughout the study area, highlyinterspecific persistent density hotspot of CWCs co-occurrence were discovered, with a total extension of 4.05 km2 where all species co-occur. Although studies on the effect of environmental and anthropogenic factors that impact the distribution of these species of conservation interest remain scarce, the results of this study offer useful guidance for decision-makers to develop necessary conservation measures. [ABSTRACT FROM AUTHOR]

The Marine Strategy Framework Directive (MSFD, 2008/56/EC) was adopted to achieve a Good Environmental Status (GES) in the EU's marine waters and to protect resources and ecosystem services, including the deep-sea waters and seafloor. The deep sea (below 200 m) is the largest biome on Earth, and its biodiversity plays a key role, despite being strongly threatened by several anthropogenic stressors, potentially affecting some ecosystem functions. Among the main deep-sea structuring species, the habitat-forming cold-water corals (CWCs) are known to form Vulnerable Marine Ecosystems (VMEs). In the Mediterranean Sea, in the last two decades, a significant effort has been devoted to unveiling the distribution, extension and ecological role of scleractinian CWCs (Madrepora oculata and Desmophyllum pertusum), but quantitative data on their conservation status are very limited. Because of their ecological importance and vulnerability, Italy has extended the implementation of the MSFD to the deep sea, carrying out specific monitoring programmes on these scleractinian CWCs. In this regard, this study established, for the first time, an extensive standardized baseline for national monitoring programmes focusing on two recently discovered upper bathyal areas dominated by scleractinian CWCs (Dohrn Canyon and Corsica Channel). The goal was to evaluate the ecological status of the bathyal biogenic reefs using traditional diversity and impact variables as well as the innovative photogrammetry tool. In both areas, the investigations have increased the knowledge about the extent of the habitat and new CWC assemblages in good health conditions were discovered. The pressure extent is limited with respect to the total extent of the CWC habitat, accounting for approximately 32% and 63% of the fishing - related items entangled on structuring species. The photogrammetric approach showed a deviation of about 33% in the measurement of the population size structures. Moreover, the use of a standardized operative protocol has been proposed to obtain reliable, coherent, and comparable data for future monitoring activities. This approach improved scientific knowledge for the two studied areas and it is pivotal in defining long-term monitoring activities useful to assess the effectiveness of specific protection measures, for these VMEs. • The Good Environmental Status of two upper bathyal biogenic reefs was assessed. • Conventional imaging and innovative photogrammetry analysis were applied. • A monitoring protocol under Marine Strategy Framework Directive was proposed. • No extensive habitat destruction threatening environmental integrity was observed. • The information collected will be used as baseline for future monitoring cycles. [ABSTRACT FROM AUTHOR]