Programma della conferenza

Mangrove habitats are known to provide essential ecosystem services to tropical countries around the world. These habitats are considered extreme for the organisms living within them, because they are subject to high temperatures, and substantial fluctuations in salinity levels and ultraviolet radiation. Among these organisms are the algae, a group of primary producers often found in association with mangrove prop roots and pneumatophores. To cope with the extreme conditions, algae are known to produce interesting osmolytes and secondary metabolites. In the Republic of the Maldives, mangrove-associated algae are extremely understudied. After carefully preparing an updated checklist of algae reported in the country, we found that only six benthic algal species haveb been reported in association with mangroves, and no information about their chemical composition is currently available. We conducted a field survey of algal diversity in the Maldivian mangroves from two central and two northern atolls and analyzed their chemical profile by GC and HPLC, with particular regards to low molecular weight carbohydrates and the UV-absorbing molecules mycosporine-like amino acids. The predominant taxa observed were members of the families Rhodomelaceae (Rhodophyta) and Cladophoraceae (Chlorophyta), which showed significant qualitative and quantitative differences in chemical composition across sites. Additionally, we discovered the presence of an algal taxon commonly observed in association with mangroves around the world, but previously unreported from the Maldivian mangroves. The explored habitats showed diverse geomorphological and environmental characteristics across sites, thus providing an interesting ground to study patterns in algal osmolyte and secondary metabolite production. Understanding the diversity and chemical composition of Maldivian mangrove-associated algae will help us understand the contributions of these important organisms to these essential ecosystems.

Marine ecosystems are currently experiencing rapid changes, characterized by rising temperatures and more frequent extreme climatic events, which are having profound impacts across all levels of the ecological hierarchy. Marine heat waves (MHWs) and subsequent extreme storms pose significant threats to marine communities, causing alterations in their structure and composition. Understanding how key benthic structuring species respond to these environmental changes has become crucial, as local biodiversity relies heavily on their conservation status. The larval stage plays a particularly pivotal role in the life cycle of sessile organisms, facilitating the maintenance of local populations and the dispersal of species. Despite its critical importance, there remains limited understanding of how larval stages respond to environmental changes across many taxa. This study specifically investigates the response of the larval stage of a significant Mediterranean endemic habitat-former, the orange coral Astroides calycularis (Pallas 1766), under realistic single and multiple stressor conditions using manipulative mesocosm experiments. Our experiments exposed coral larvae to heat-temperature spikes, MHWs, and combined MHWs with dropping salinity treatments. We examined metabolic performance responses of the early-life stage, as well as larval survival and settlement abilities. Results indicated that rising temperatures and decreasing salinity significantly impair the species' performance, resulting in accelerated metabolism, faster settlement rates, and increased mortality. These findings are essential for comprehending and predicting species distribution and population dynamics under current and future environmental change scenarios. They also shed light on the fate of biodiversity associated with this habitat-forming species in the Mediterranean.

Honeybees (Apis mellifera L.) provide an essential ecosystem service as pollinators. However, given their characteristics -big colonial size, generalist diet, wide foraging ranges- and their management, honeybees are capable of monopolising trophic resources (pollen and nectar), potentially impairing the survival of other species of wild bees. Competition can be especially harsh in small and homogeneous ecosystems, such as small islands. We investigated such potential competition on Giannutri, a small island within the Tuscan Archipelago National Park, in which 18 hives of managed honeybees are seasonally introduced since 2018. Spatial and flower-visits overlap between honeybees and wild bees suggests potential exploitative competition. Our experimental approach was to manipulate honeybees’ abundance by closing and opening the beehives, to obtain 2 experimental conditions in which we assessed: a) the abundance of different species of Apoidea, through transect walks; b) trophic resources availability, through quantification of nectar volume (on Teucrium fruticans L. and Salvia rosmarinus Spenn.) and presence/absence of pollen (on T. fruticans); c) foraging pattern behaviours of target wild bees (Anthophora dispar Lepeletier and Bombus terrestris L.), through focal behavioural sampling and observation plots. We documented: a) a decline in the number of individuals of the target species over 4 years; b) a lower availability of trophic resources in days with presence of honeybees; c) changes in foraging behaviour patterns in target wild bees (e.g. less time spent in nectar suction on individual flowers by wild bees in presence of honeybees). Our results suggest that honeybees can have a detrimental effect on wild bees. Giannutri, therefore, represents not only a study area in which we want to safeguard wild bees' populations, but also a model system of a small Mediterranean landscape. In view of this, our findings can drive the draw up of new guidelines towards a more aware and sustainable beekeeping practice.

The health of bees and other pollinating insects is increasingly threatened by human activities, which include factors like climate change, habitat destruction, parasitic infections, diseases, and notably, environmental pollution and pesticide use in agriculture. Population dynamics, the presence of Varroa destructor mites, and ecotoxicological impacts were examined in two apiaries subjected to varying levels of anthropogenic pressure. Biomarkers of neurotoxicity (acetylcholinesterase (AChE) and carboxylesterase (CaE)), metabolism (alkaline phosphatase (ALP)), biotransformation (glutathione S-transferase (GST)), and immune system (lysozyme (LYS), phenoloxidase (POx), and prophenoloxidase (proPOx)) were analyzed in different worker sub-castes of Apis mellifera. Specifically, we assessed biomarker responses based on sub-caste (newly formed, adult builders, and foragers), season (spring, summer, and autumn), and potential sources of contamination. The findings revealed a physiological oscillatory pattern in population dynamics and varroa levels, attributed to control treatments for parasitosis. Enzymatic activity values varied among worker sub-castes across the three seasons, with AChE activity being lower in newly formed bees and builders compared to foragers, while GST activity was higher in newly formed bees. The application of synthetic pesticides against varroa likely resulted in toxicological effects on bees treated for parasitosis. This study enhanced our understanding of the physiological activities of the investigated enzymes in different castes, providing deeper insight into the sub-lethal effects of pesticides and environmental contaminants, and how climate change and other stressors influence the population dynamics of these insects.

Connectivity within networks of marine protected areas (MPAs) is key to support the resilience of fish communities in the long run and scale up the benefits provided by single MPAs. Therefore, connectivity assessments are crucial for designing effective conservation strategies for fish populations. In the context of the Italian national research project “Reconnect”, we analyse connectivity among existing and candidate MPAs in Sicilian coastal waters using the dusky grouper Epinephelus marginatus as a model species, in view of (i) its key ecological role in Mediterranean rocky reef ecosystems, (ii) its vulnerability to intensive fishing and (iii) the concurrent knowledge gap on its population structure and dispersal features. We study connectivity using an individual-based bio-physical model and simulate larval dispersal with a Lagrangian approach. Species distribution models – providing predicted biomass of E. marginatus in space – are used as initial conditions of the simulations and are generated based on field data gathered either via underwater visual censuses (UVCs) or baited underwater videos (BUVs), depending on bathymetric conditions. To harmonise the data from these two census methodologies, their statistical relationship was explored on a pre-existing dataset by fitting various statistical regression models (e.g., generalised linear models, two-parts models). This analytical framework allows for the elaboration of a set of connectivity metrics to (i) assess the performance of the existing MPAs network in the study area and (ii) identify potential connectivity hotspots where to funnel future conservation effort and reduce anthropogenic disturbance, ultimately contributing to science-informed MPAs spatial planning.

Transitional environments in deltaic areas host a diverse range of aquatic ecosystems, each characterized by distinct living communities and ecological functions. Understanding these ecosystems is essential for their management and biological conservation. This study investigates the conservation value and ecosystem functioning of eight aquatic systems within the Po River Delta Park (Italy), one of Europe's most significant transitional areas, using fish communities as indicators based on presence/absence data.The analysis considered seasonal patterns in species occurrences and respective functional traits. Initially, multivariate analyses were performed to assess the impact of environmental characteristics on community composition. Subsequently, conservation values were measured through community composition, and the functional roles of wetlands were evaluated by examining fish traits related to habitat use and feeding mode. The contributions of different wetlands to alpha and beta diversity were also explored.The results indicated that water level patterns (artificial vs. tidal) and wetland surface area were the most influential factors in determining the species composition of fish communities in both taxonomic and functional terms. Coastal wetlands exhibited a higher number of species, including protected ones, indicating a greater conservation value. Functional beta diversity analysis revealed that migratory species significantly contribute to functional beta diversity, emphasizing the role of wetlands as nurseries and feeding grounds. During winter and autumn, detritivorous species primarily drive beta diversity, while planktivorous and piscivorous species are more influential in spring and summer, highlighting trophic seasonal variations.Overall, the findings demonstrate that fish communities are effective indicators for describing and monitoring ecosystem functioning in managed transitional waters, providing valuable insights for guiding the environmental management of these unique ecosystems.