Giovanni Giacalone

This study presents the first recorded observation of the calanoid copepod Calanopia elliptica (Dana, 1849–1852) in the waters between the southern coast of Sicily (Italy) and Malta, and the Central Mediterranean Sea in general. This area is characterised by heavy traffic of cargo ships passing through the Suez Canal to enter and exit the Mediterranean Sea. Moreover, water masses from both eastern and western basin flow through the Strait of Sicily and highly influence the waters surrounding Malta. These two aspects make this area suitable for the arrival of a vast array of lessepsian and Atlantic invaders, brought by current or ballast waters, or a combination of both. For this reason, a total of 32 zooplankton samples collected during the summer of 2025 were analysed for species diversity and abundance. A total of 133 organism taxa were identified to the lowest taxonomical level possible. General community analyses revealed that the composition of the zooplanktonic community across the study area is tied mainly to water column stability. The consistent frequency (53.13%) but relatively low abundances of C. elliptica (maximum 1.747 ind/m³) across multiple samples may indicate the onset of a new colonisation, as its known invasion range had previously been confined to the eastern basin of the Mediterranean Sea. Analyses suggest that the abundance of this copepod in the study area is mainly tied with low dissolved oxygen levels and temperatures, while seemingly unrelated to the other environmental parameters and to the time of the day in which it was sampled. These findings are just at the start of the analysis of a time series of zooplankton samples in the area. Hence, future studies based on it are necessary to identify trends in the abundance of this species over the past and future years, as well as any potential impacts on the native community.

Socio-economic and human activities represent the major impacts on marine pollution affecting the marine ecosystems, raising increasing scientific, societal and policy interest due to the long-term consequences for the environment and the coastal economies.Especially in semi-enclosed basins such as the Mediterranean Sea, the accumulation of marine litter, and particularly plastic items, represents a serious issue, intensified by intense anthropogenic pressure, high coastal population density and circulation patterns.The identification of plastic litter sources and their tracking on the sea surface represents a first step to identify the most vulnerable areas and accumulation hotspots.To achieve this goal, the hydrodynamic Lagrangian model Track Marine Plastic Debris (TrackMPD) was applied in the strait of Sicily considering rivers as input sources of plastic litter. The area is characterized by the presence of important hydrodynamic processes, including sea currents, mesoscale eddies, upwelling events etc. The quantities of plastic items to be released by rivers into the marine environment were estimated considering the data provided by “The Ocean Cleanup” website.The model’s results were compared with the in-situ data collected during the monitoring campaign conducted by “Agenzia Regionale per la Protezione ambientale” (ARPA) and “Consiglio Nazionale delle Ricerche” (CNR) in August 2018 and 2019, where microplastic items were sampled using a Manta net along fixed transects.Since the actual discharging point and period of the debris recorded by ARPA-CNR were unknown, the comparison was performed by considering 105 scenarios, each characterized by a different starting day of the daily particle release. The scenarios span a temporal interval from May up to the sampling day; for each subsequent scenario, the discharging time window progressively decreases as the release start date is shifted forward by one day.The accumulation and density maps were realized for each scenario. A buffer area was considered around each transect and the sum of the simulated particles within it was calculated, comparing the results with the microplastics sampled. The comparison between the simulations and the in-situ campaigns was performed by computing the coefficient of determination, R².The results highlight the difficulties validating the hydrodynamic model by using the in-situ data, indeed very low R2 values were performed for each scenario.Further developments of this work include the determination of realistic scenarios of plastic discharge into the marine environment through a detailed study of the territory, considering local productive activities and the resulting pollutant generation, coupled with targeted sampling campaigns to provide data for model implementation and/or validation.

Understanding recent thermohaline variability is essential to assess ongoing changes in circulation and water-mass properties in the western Mediterranean Sea. This study investigates the spatial and interannual evolution of surface and intermediate water masses along the Ligurian and Tyrrhenian continental shelves utilizing a unique dataset of twelve summer CTD surveys collected between 2009 and 2022 as part of the EVATIR programme. In situ observations are complemented by satellite-derived sea surface temperature, atmospheric forcing data, and three-dimensional ocean reanalysis products to contextualize the observed variability within a coherent physical framework.The CTD data reveal a transition from a relatively cold–fresh regime toward a warmer and more saline state affecting both the surface and intermediate layers of the southern Tyrrhenian shelf. In this sector, Atlantic Water shows clear decadal-scale changes, marked by increasing salinity at its core and a significant warming at the salinity minimum (approximately +0.23 ◦C yr−1).Similar changes are observed within the intermediate layer (90–200 m), which exhibits a statistically significant long-term warming accompanied by increasing salinity, indicating that the thermohaline transition extends throughout the upper water column. By contrast, the central Tyrrhenian and Ligurian shelves do not display statistically significant long-term trends, with interannual variability remaining the dominant signal.The observed thermohaline evolution is closely associated with changes in winter surface conditions. February sea surface temperature fields show a marked contraction of cold winter signatures after 2013, suggesting a reduction in the spatial extent and intensity of winter surface cooling. Consistently, the analysis of atmospheric forcing and air–sea heat fluxes reveals weaker northerly winds and decreased winter buoyancy loss in recent years, conditions that are less favourable for deep winter mixing and the ventilation of ransitional intermediate waters. Additional dynamical support is provided by three-dimensional Copernicus Marine reanalysis fields, which indicate a progressive shoaling of winter mixing and a reduced penetration of cold waters into intermediate depths within the Bonifacio Cyclonic Gyre. Overall, the results document a regime transition in water-mass properties along the western Italian shelf and emphasise the sensitivity of shelf hydrography to changes in winter atmospheric forcing.

Understanding the impact of climate change on thermohaline dynamics in the western Mediterranean Sea is essential for assessing shifts in regional circulation and water mass formation. This study analyzes data from twelve summer oceanographic surveys conducted between 2009 and 2022 along the Ligurian and Tyrrhenian continental shelf. Results reveal a decadal-scale warming and salinification of both surface and intermediate layers, leading to enhanced water column stratification. On the northern Sicilian shelf, AtlanticWater exhibited a salinity increase of +0.02 yr⁻¹ and a potential temperature rise of +0.40 °C yr⁻¹ between 2011 and 2022, driven by sustained surface warming and advection of Ionian Surface Water from the eastern Mediterranean. This warmer and saltier water mass also affected intermediate depths, modifying vertical density gradients. The influence of Ionian Surface Water peaked around 2016, coinciding with the progressive warming of Tyrrhenian Intermediate Water due to the absence of strong winter cooling after 2014. These hydrographic changes are linked to the Adriatic–Ionian Bimodal Oscillating System and the transition of the Northern Ionian Gyre from a cyclonic to an anticyclonic state, which modulates the inflow of intermediate waters through the Sicily and Messina Straits. On the Ligurian shelf, Western Intermediate Water showed moderate warming (+0.06 °C yr⁻¹) until 2017, followed by cooling, and a salinity increase until 2019. These findings underscore the importance of inter-basin connectivity and the need for integrated monitoring and modeling to understand and anticipate climate-driven variability in the Mediterranean Sea.

Age determination through reading annual rings in whole otoliths is a complicated, time-consuming task that can lead to errors in population age structure, negatively affecting marine fish management plans. Recently, Fourier transform near-infrared spectroscopy (FT-NIRS) has been successfully used to evaluate annual age, at least in several long-life fish species. European anchovy (Engraulis encrasicolus) is an important pelagic species for its ecological role and socioeconomic value. In the Mediterranean Sea, anchovy stocks are regularly monitored for assessment purposes, and fish age is calculated by traditional otolith reading. In the present study, anchovies, caught over a decade (2012 to 2023) during on-board surveys in four different areas (i.e., North Tyrrhenian, South Tyrrhenian, North of Sicily, and Strait of Sicily), provided an otolith collection used to acquire absorption spectra by FT-NIRS. These spectra were processed to optimize calibration models, and the best linear models obtained revealed a good predictability for anchovy annual age (coefficient of determination of 0.90, mean squared error 0.3 years, bias < 0.001 years). The calibration model developed for all regions combined proved more robust than the models for each area, demonstrating its efficacy for the entire study area. FT-NIRS analyses proved suitable for predicting age, when applied to E. encrasicolus individuals within the age range of 0 to 3, also when compared to traditional aging methods. Moreover, this methodology improved the standardization of age estimates. Finally, this preliminary study encourages the further application of FT-NIRS also to short-life pelagic species involved in stock assessment plans.

In this study, hydroacoustic data collected with a scientific echosounder working at two frequencies (38 and 120 kHz) over the continental shelf off the southern Sicilian coast were used in order to investigate the relationship between fish schools and plankton patches. Specifically, image analysis algorithms were applied to raw echograms in order to detect and characterise pelagic fish schools and plankton aggregations, considered as a proxy of food availability. The relationship was first investigated using estimated total plankton biomass over the whole water column and, second, by dividing the study area into three sub-regions and further distinguishing plankton patches between the surface and the bottom. In the relatively lower plankton abundance areas of Zone 1 (northern sector of the study area), results showed an inverse relationship between the biomass (and density) of fish schools and the biomass of co-occurring plankton patches located close to the bottom. Instead, over the Sicilian-Maltese shelf (Zone 3), characterised by higher plankton abundances, a direct relationship was found when using plankton data from the whole water column. The observed difference between Zones 1 and 3 is probably due to diverse dominant fish species in the two sub-regions.