https://www.um.edu.mt/library/oar/handle/123456789/144927 2026-10-29T03:41:46Z https://www.um.edu.mt/library/oar/handle/123456789/150571 Title: Invasiveness versus sustainability : supply chain perceptions of Opuntia ficus-indica in the Maltese food system Abstract: This research seeks to outline key contradictions in the agricultural uses, cultural values, economic opportunities, and ecological practices associated with the prickly pear cactus, Opuntia ficus-indica (OFI). Understanding contradictions in perspectives on invasive species like OFI aids in informing policy surrounding the environmental management of such species and contributes towards global research of invasive-food system integration, which is becoming increasingly important as climate change threatens traditional agricultural systems. This project analyzes necessary trade-offs associated with managing OFI in Malta through supply chain perceptions and valuation in primary markets, and consumer-side interviews in informal markets to capture perceptions and uses of the prickly pear cactus. Alongside a policy and literature review on historic and current uses, markets, and management practices, these data were analyzed through reflexive thematic analysis to create themes. Three major findings emerged from these analyses: contradictions between perceived nativeness and nonnative origins; nuanced views of plant classification impacted by cultural and food systems associations; and limited commercial development and institutional support despite OFI's climate resilience. A SWOT analysis was then used to evaluate potential futures for OFI. These findings presented three key pathways for OFI: increased investment, continuing current practices, and increased environmental regulation. These findings ultimately suggest that the role of OFI must be understood by the sum of its functions, as an environmental concern, agricultural resource, commercial product, and a cultural symbol. Any pathways for OFI are dependent on how stakeholders weigh trade-offs between these functions. Description: MSc. (EMS)(Melit.) 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150565 Title: Seasonal variability and multi-decadal trends of the mixed layer depth in the central Mediterranean Abstract: This study examined seasonal variability and multi-decadal trends of the Mixed Layer Depth (MLD) in the central Mediterranean. The primary objectives included addressing regional research gaps and evaluating three estimation methodologies to determine the most physically consistent approach for the region. The methods examined were the vertical temperature gradient, fixed temperature threshold, and density threshold (TEOS-10). MEDSEA_MULTIYEAR_PHY_006_004 physical reanalysis product from Copernicus Marine Service was used to provide daily temperature and salinity fields at a 1/24° (~4.5 km) horizontal resolution across 141 vertical levels. These reanalysis data were used to identify long-term trends and shifts in the MLD through daily estimates analyzed over 39 years, from 1 January 1987 to 1 January 2026. The findings indicate that the density threshold method (TEOS-10) was the most suitable framework. The most noteworthy result was a statistically significant spring shoaling trend of -0.87 m per decade that is indicative of seasonal stratification occurring earlier every decade. A possible association between MLD anomalies and to the presence of a gyre is identified. The results contribute to current regional knowledge of seasonal variability and multi-decadal trends, identify a statistically significant shoaling trend, and identify a possible association of MLD anomalies to the Malta-Sicily Gyre (MSG). Description: MSc. (EMS)(Melit.) 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150269 Title: Mapping maritime pollution risk and coastal vulnerability around Malta Abstract: Maritime transport is essential to global trade and island connectivity, but it also creates persistent environmental risks for coastal states located near major shipping corridors. Malta is particularly exposed because of its central Mediterranean position, proximity to dense cargo and tanker traffic, and dependence on coastal resources, tourism, fisheries, and marine infrastructure. This project assessed maritime pollution risk and coastal vulnerability around the Maltese Islands by integrating Automatic Identification System (AIS) vessel-position data, OpenDrift oil-spill simulations, and GIS-based shoreline exposure mapping. AIS data were used to identify two maritime corridors of interest; an offshore northern corridor, and a nearshore south-eastern corridor. Randomized release points were generated within these corridor boundaries and used as starting locations for OpenDrift/OpenOil simulations of a 10 cubic meters generic diesel release under selected wind, wave, and surface-current conditions. Model outputs were exported as particle trajectory data and mapped in GIS to evaluate offshore dispersion, nearshore movement, and coastal-contact patterns. Results showed that offshore scenarios generally remained separated from the Maltese coastline during the modelled period, while nearshore scenarios produced greater coastal relevance, including trajectories moving adjacent to Malta and particles classified as stranded or coastal-contact points. Coastal-contact locations were spatially uneven, with exposure concentrated along selected eastern, south-eastern, and southern shoreline sectors. These findings indicate that maritime pollution risk around Malta is shaped by the interaction between vessel location, environmental forcing, release proximity, and coastal receptors. The workflow provides a spatial decision-support framework for monitoring, emergency-response planning, and future coastal vulnerability assessment. Description: MSc. (EMS)(Melit.) 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150267 Title: Marine heatwaves in the central Mediterranean : frequency and spatial distribution (2008-2025) Abstract: The Mediterranean Sea is warming faster than the global ocean average, making its semi enclosed, relatively shallow basin particularly exposed to extreme thermal events. Marine Heatwaves (MHWs), prolonged periods of anomalously high ocean temperature, offer an ecologically meaningful way to characterize this warming because they capture disruptive extremes rather than gradual mean trends. This study quantifies the frequency of surface MHWs in the waters around the Maltese Islands, including the 12-nautical-mile territorial sea and the 25-nautical-mile Fisheries Management Zone (FMZ), over a 17-year period from 2008-2025. Daily ultra-high-resolution sea surface temperature analyses from the Copernicus Marine Service were used to construct, for every grid cell, a seasonally varying daily 90thpercentile threshold. Following the minimum-duration criterion of Hobday et al. (2016), periods in which temperature exceeded this threshold for at least five consecutive days were classified as MHW events, and events were counted for every grid cell and mapped across the domain. A representative cell south of Malta was used to validate the detection procedure. Across the domain, the mid-August 90th-percentile threshold ranged from 27.7 °C to 29.6 °C (mean 28.6 °C), and the number of detected events per grid cell over the study period ranged from 26 to 53, with a domain mean of approximately 40. Exposure was spatially uneven. Event frequency was highest in the western and northwestern waters and lowest in the waters immediately south and southeast of the Maltese Islands. At the validation cell, 37 events were detected, and threshold exceedances recurred in most summers, becoming more frequent toward the end of the record, with the warmest peak in 2023. These results show that recurrent surface thermal extremes are pervasive but spatially structured across Maltese waters, with direct relevance to fisheries management, marine spatial planning, and climate-adaptation planning. Methodological limitations, including a simplified climatology, a surface-only focus, and a baseline drawn from a warming period, are discussed, and depth-resolved analysis is identified as a priority for future work. Description: MSc. (EMS)(Melit.) 2026-01-01T00:00:00Z