Massimo Celio

The trophic status of coastal environments is largely controlled by nutrient inputs, particularly nitrogen and phosphorus, whose excess may lead to eutrophication. The northern Adriatic Sea has historically been affected by these processes, with notable impacts on water quality. This study analyses a time series (2015–2024) collected at six offshore sites in the Gulf of Trieste within the Marine Strategy Framework Directive (MSFD) Descriptor 5. Dissolved Inorganic Nitrogen (DIN) showed marked spatial variability, with 19.9% of samples exceeding the threshold of 6.85 µM. Phosphate concentrations were low (mean 0.17 µM), indicating strong P-limitation (mean N:P ratio = 277). Chlorophyll a concentrations (mean 0.9 ± 0.1 µg L⁻¹) reflected oligotrophic conditions, although 17% of samples exceeded 1.5 µg L⁻¹. Time-series analyses revealed a significant warming trend (+0.1 °C yr⁻¹; p = 0.022) and a significant decrease in chlorophyll a (p = 0.038), while no significant trends were observed for nutrients, dissolved oxygen or TRIX. TRIX values (0.8–6.9) indicated overall good to high ecological status. A trophic–hydrological gradient highlighted the positive influence of river inputs and precipitation on nutrient availability and trophic conditions. These results provide a solid quantitative baseline for MSFD assessments and underscore the role of hydrological and meteorological forcing in shaping trophic variability in the Gulf of Trieste.

The present study utilised a comprehensive, long-term dataset of toxic phytoplankton (2001–2022) to analyse the relationships between the abundance, distribution, and seasonal trends of toxic phytoplankton, as well as the influence of various sampling methods, physico-chemical parameters, nutrients, and meteo-climatic parameters. The data were obtained through institutional monitoring at four selected sites dedicated to shellfish farming in the Gulf of Trieste (Adriatic Sea, Italy). The results show significant gradients in the spatial distribution of toxic phytoplankton and clear seasonal patterns in regard to the physico-chemical parameters and nutrients. Toxic phytoplankton abundance peaked in late winter/early spring and early autumn, depending on the genus considered. Significant correlations suggest that rainfall influences the nutrient levels and the proliferation of toxic phytoplankton. The time series analysis highlighted significant increases in temperature, salinity, and nitrogen species, during the study period, and decreases in silicon and phosphorous, while chlorophyll a and the overall phytoplankton abundance remained relatively stable, except for a significant decrease in Lingulodinium from 2015 to 2022. This preliminary assessment provides a valuable basis for further approaches (e.g., continuous in situ measurements, modelling, machine learning) to investigate the potential impact of climate variability on toxic phytoplankton dynamics in the Gulf of Trieste and to support mussel-farming management from both health and environmental perspectives.

Dissolved oxygen (DO) is a key element for the survival of marine organisms and is a supporting element in the current Water Framework Directive (WFD). DO deficiency is a common event that occurs in coastal environments such as estuaries and lagoons, but a long-term DO database that helps detect daily and seasonal oscillations is difficult to obtain with commonly used sampling and analytical procedures. In this work, a network of multi-parametric probes was deployed in the Marano and Grado Lagoon (northern Adriatic Sea, Italy) in order to obtain a dataset from the continuous monitoring of DO and complementary parameters. DO showed a high degree of variability both in terms of spatial and seasonal distribution and was dependent on solar radiation and water temperature. During the summer and in areas characterised by scarce water renewal, DO was below the threshold set as the minimum requirement for aquatic life, thus some water bodies (WBs) were classified as moderate sensu WFD. The inputs of freshwater discharge from inland and marine waters during tides are, however, able to well oxygenate most of the lagoon. These results will be useful in supporting the management and protection of this vulnerable environment.

Along shipping lanes the density of the ships is very high resulting, in a non-negligible probability of pollutant release in the sea. So, it is extremely important to react promptly to an oil spill emergency, to avoid that the pollutant spreads. This work describes services that are ready to use in case of oil spill. Services integrate weather and marine forecasts into a numerical model simulating the dispersion of the oil slick. Details are presented, together with applications during simulated ship collisions or accidental released along the routes. The focus is on the Adriatic area.

During the last century, human activities have exerted an increasing pressure on coastal ecosystems, primarily inducing their eutrophication, with a more recent partial mitigation of this phenomenon where improvements of environmental management practices were adopted. However, a reanalysis of the pressures on coastal zones and surrounding drainage basins is needed because of the alterations induced nowadays by the climate changes. A comparative analysis of long-term oceanographic and environmental data series (1986–2018) was performed, in order to highlight the effects of anthropogenic and climatic disturbances on the phytoplankton community in the Gulf of Trieste (GoT). After the 1980s, the decline in phytoplankton abundance was matched to increasing periods of low runoff, an overall deficit of the precipitation and to a decrease in phosphate availability in the coastal waters (−0.003 µmol L⁻¹ yr⁻¹), even in the presence of large riverine inputs of nitrogen and silicates. This trend of oligotrophication was reversed in the 2010s by the beginning of a new and unexpected phase of climatic instability, which also caused changes of the composition and seasonal cycle of the phytoplankton community. Beyond the management of nutrient loads, it was shown that climatic drivers such as seawater warming, precipitation and wind regime affect both nutrient balance and phytoplankton community in this coastal zone.

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.