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The availability of marine habitats maps remains limited due to difficulty and cost of working at sea. Reduced light penetration in the water hampers the use of optical imagery, and acoustic methods require extensive sea-truth activities. Predictive spatial modelling may offer an alternative to produce benthic habitat maps based on complete acoustic coverage of the seafloor together with a comparatively low number of sea truths. This approach was applied to the coralligenous reefs of the Marine Protected Area of Tavolara - Punta Coda Cavallo (NE Sardinia, Italy). Fuzzy clustering, applied to a set of observations made by scuba diving and used as sea truth, allowed recognising five coralligenous habitats, all but one existing within EUNIS (European Nature Information System) types. Variable importance plots showed that the distribution of habitats was driven by distance from coast, depth, and lithotype, and allowed mapping their distribution over the MPA. Congruence between observed and predicted distributions and accuracy of the classification was high. Results allowed calculating the occurrence of the distinct coralligenous habitats in zones with different protection level. The five habitats are unequally protected since the protection regime was established when detailed marine habitat maps were not available. A SWOT (Strengths-Weaknesses-Opportunities-Threats) analysis was performed to identify critical points and potentialities of the method. The method developed proved to be reliable and the results obtained will be useful when modulating on-going and future management actions in the studied area and in other Mediterranean MPAs to develop conservation efforts at basin scale. [ABSTRACT FROM AUTHOR]

The gorgonians Paramuricea clavata (Risso, 1826) and Eunicella cavolini (Koch, 1887) are important habitat-forming species within the Mediterranean coralligenous habitats, creating complex, three-dimensional forests that greatly contribute to the underwater landscape of the coastal hard grounds. Dense forests of both species are present within the Portofino Marine Protected Area (Ligurian Sea, NW Mediterranean Sea), showing a distinct bathymetric separation and site-specific differences. Quantitative evidences obtained with a monitoring census conducted in 2016 in 16 sites within the MPA support the existence of a widespread damage on these populations partially due to the mechanical injuries inflicted by recreational and professional demersal fishing gears. Considering all the studied populations, it resulted that 53% of the colonies of P. clavata and 36% of the colonies of E. cavolini were showing traces of impact, of which 10% in P. clavata and 7% in E. cavolini were due to direct entanglements with lost longlines. In the last decades, recurrent massive mortalities related to temperature anomalies and storms, have greatly reduced the gorgonian populations in this area and fishing impact severely affects survived or recovering colonies. Considering the vulnerable status of these species, and the increasing stress due to climate change, a correct management of the anthropic pressures is strongly needed to help preserving these relevant ecosystems. Image 1 • - Paramuricea clavata and Eunicella cavolini are important ecosystem-engineers. • -Dense forests of these species thrive inside the Portofino MPA (NW Mediterranean). • -51% of P. clavata and 36% of E. cavolini colonies were impacted by fishing gears. • -The density of impacted colonies was strongly related to the fishing effort in the area. • -A management of fishing pressures is needed to preserve these relevant ecosystems. [ABSTRACT FROM AUTHOR]

The main aims of Marine Protected Areas (MPAs) are the conservation of natural habitats and their biological resources, together with the promotion of an eco-compatible economic fruition. In Mediterranean MPAs, the main threats for hard bottom benthic communities come from fishing and mass tourism, in terms of boating and SCUBA diving. The Portofino MPA (Ligurian Sea, North-western Mediterranean Sea) is one of the top diving destinations in Europe and currently hosts an average of 40,000 dives per year, which are mainly carried out along coralligenous cliffs, a habitat of European Community interest, particularly vulnerable to mechanical damages due to the fragility of its numerous calcified species. The aim of this paper is to evaluate the effects of recreational SCUBA diving on benthic ecosystems characterised by the presence of red coral and other associated fragile species. The impact was assessed through the analysis of the biomasses of target organisms (Corallium rubrum, Leptopsammia pruvoti, Madracis pharensis , and six species of bryozoans) whose fragments were found in the sediments at the base of the cliff. The amounts of these fragments inside the detritus in highly frequented sites were significantly higher than those measured in undisturbed sites, of up to 10 times. Our data suggested a recurrent mechanical action, with also very recent breakages, as demonstrated by the occurrence of living, freshly detached organisms. Red coral and other calcified species may be sensitive also to natural (heavy storms) and human (fishing) mechanical pressures other than diving: the characterization of these impacts in the study sites, however, indicates divers frequentation as the major contributor to the damages inflicted and suggests the need for specific management measures. • Evaluation of SCUBA diving effects on calcified, fragile species. • Comparison among two frequented and two pristine sites in the Portofino MPA. • Impact assessed comparing specimens' abundance on cliff and in underlying sediment. • Target species fragments in sediments 10 times higher in highly frequented dive spots. • MPA management urges to find a balance between fruition and mitigation of impacts. [ABSTRACT FROM AUTHOR]