The aim of the present study was to propose a biotic index (North Adriatic Mesophotic BiogEnic Reefs, NAMBER) suitable for assessing the ecological quality of the mesophotic biogenic reefs of the northern Adriatic continental shelf based on photographic sampling. At each of the 20 study sites, the degree of bioconstruction (expressed as percentage cover of crustose coralline algae), the α‐diversity (expressed as the mean number of taxa), and the degree of sensitivity to human disturbance and climate change (based on literature data and expert judgement) of the benthic assemblages were selected as descriptors and combined in the NAMBER index, using the best values that the three metrics can currently achieve in the studied region as a reference. The study highlighted that there was large spatial heterogeneity among reefs and high variability in the ecological quality values obtained by NAMBER, ranging from bad to high. The index indicates that reefs lying furthest from the coast, under substantially lower anthropogenic pressure, have a generally higher status of environmental quality. However, a clear geographical pattern did not emerge, as reefs close together often had different ecological qualities. The NAMBER index, which combines three ecological descriptors, in accordance with the requirements of the European Marine Strategy Framework Directive, represents a specific adaptation to the northern Adriatic Sea of a multimetric index previously developed for the north‐western Mediterranean Sea, capitalizing on previous knowledge and research efforts. This multimetric biotic index provides an effective standardized tool for monitoring programmes and environmental impact assessments in the northern Adriatic mesophotic biogenic reefs and lays the foundation for ecosystem‐based management and conservation in this basin.

The endemic Mediterranean bivalve Pinna nobilis is a typical example of an autogenic ecosystem engineer in sedimentary environments, as it modifies the substrate, creates new complex 3D habitats and concentrates various species, thus increasing local biodiversity. Despite the significant loss of P. nobilis populations due to the epidemic mass mortality that occurred in several regions of the Mediterranean, including the northern Adriatic Sea, the numerous empty shells, still firmly anchored in the sediment, may continue to play the role of basibiont of this species. The persistence of this ecological function was here investigated on dead specimens of P. nobilis through the structural and functional study of the associated epibenthic mollusc community. A large number of mollusc taxa, characteristic of both infralittoral and sublittoral hard and soft bottoms, were identified in thirteen shells collected from four different sites in the Gulf of Trieste. Multivariate analysis revealed a clear separation between sites in terms of taxonomic composition, species abundance and biomass, with differences in expressed functional traits. Overall, considerable taxonomic and functional diversity was found, suggesting that the empty shells continue to provide a suitable habitat for a variety of molluscs that are closely linked to the surrounding environment and fulfil many different ecological functions.

Pinna nobilis, commonly known as the noble pen shell, is a marine bivalve endemic to the Mediterranean Sea. Unfortunately, due to a multifactorial disease that began affecting its populations in 2016, the species is currently facing the threat of extinction. To gain insights into the evolutionary history of P. nobilis before the mass mortality event (MME), and to obtain a comprehensive understanding of how evolutionary processes led to the adaptation of the species into the Mediterranean Sea, phylogenetic and phylogeographic analyses were carried out. The dataset analysed includes 469 sequences of COI gene fragment both from GenBank and the present study (100). The analysis performed evidenced that P. nobilis diverged about 2.5 mya, after the entrance of its ancestor into the Mediterranean Sea following the Zanclean flood (5.33 mya). Moreover, our results suggest that the starting point of colonisation was the central part of the western Mediterranean basin, with the eastern basin being populated subsequently. From a conservational viewpoint, these results provide important hints for present and future restocking plans, helping to reconstruct the pre-existing genetic variability in sites where the species became extinct.

Electric boats are thought to be noiseless, but in-situ measurements are generally rare. The Underwater Radiated Noise (URN) of 8-m Trimaran Pontoon Boat with two outboard electric engines was measured in the Miramare Marine Protected Area (Trieste, Italy), together with the URN of a fibreglass 5-m boat, with a outboard gasoline engine, for comparisons. International standards and guidelines for shallow waters were considered. URN were provided in one-third octave band and in narrow band spectra. The electric boat produced a low input of underwater noise at low frequencies. Given a low-frequency hearing sensitivity, the listening space reduction (LSR) was lower when generated by the electric than by combustion engine boat for the brown meagre, a local Teleost fish. No difference was found for the bottlenose dolphin LSR although continuous, tonal, high frequency components generated by the electric boat are expected to be highly detrimental for the bottlenose dolphin.

The growing exploitation of marine space for human activities is leading to the proliferation of artificial structures in coastal and offshore areas. Hence, improving building materials to minimize the impact of their introduction in the marine environment and to enhance their overall environmental sustainability is essential. The addition of biochar, a common carbon-rich by-product of thermochemical treatments of discarded biomass, in concrete mixtures for marine uses may lead to progresses in this perspective, combining waste recycling with carbon storage and sequestration potential. However, comprehensive evaluations of possible effects of biochar-based concrete on the marine biota are lacking to date. Here, laboratory tests and manipulative field experiments were carried out in three different sites (NE Adriatic, Mediterranean Sea) to assess whether biochar-based concrete could affect marine organisms and the colonization of micro- and macrobenthic assemblages on artificial hard substrata in shallow subtidal habitats. No relevant ecotoxicological responses to biochar exposure for several target marine organisms from different trophic levels were found. With respect to conventional concrete, adding up to 10 %wt. biochar to the mixture did not determine significant changes neither in microfouling assemblages at early stages of colonization, nor in the structure of macrobenthic assemblages and their total biomass on submerged substrata during the six-month field experiment. Although further investigations in other habitats and with different types of biochar are needed to draw generalizations, such findings highlight that biochar-based concrete can be biologically suitable for marine constructions and could contribute to reduce the carbon footprint of marine artificial structures.

For the first time, the distribution and modifications of living ostracod associations present in the Gulf of Trieste (GoT) in relation to alterations caused by human activity in the last 20 years were investigated. The results were compared with the main physicochemical parameters (especially nitrogen and phosphorus) measured over the same period, which can lead to a general decrease in environmental quality. For a more in-depth analysis of the changes recorded by ostracods in the last 50 years, a period in which eutrophication and anoxia increased, we revisited the study carried out by Masoli in the GoT in 1967. The results obtained made it possible to verify how, over the last 20 years, ostracod assemblages have suffered a decrease both qualitatively and quantitatively. Most of the species recovered show characteristics of opportunism and tolerance to environmentally stressful conditions, high organic matter concentrations, and oxygen deficiency. The ostracods analyzed in 1967 showed similar results with few dominant opportunistic species. We verified how ostracods recorded in GoT, similar to Mollusks and Foraminifera, have been impaired by the possible environmental crisis linked to the recurrence of mucilage and hypoxic events documented for the GoT in the last 50 years. Finally, a comparison with the best environmental conditions found in the Marine Nature Reserve of Miramare (MPA) allowed us to emphasize the important role of protected areas to avoid loss of biodiversity due to urbanization.