https://www.um.edu.mt/library/oar/handle/123456789/126305 2026-04-14T13:07:33Z 2026-04-14T13:07:33Z https://www.um.edu.mt/library/oar/handle/123456789/129802 2024-12-10T16:31:02Z 2024-01-01T00:00:00Z

Title: The effect of Cu, Zn and Pb contamination on microbial activity in soils of Malta Abstract: Soil microbial activities are significantly influenced by external variables including pollutants like heavy metals, that can turn from beneficial microelements to toxic and persistent polluters when excessive quantities are available. This in turn can have negative or adverse effects on the activity of soil microorganisms. The aim of this work was to study the effect of increasing concentrations of Cu, Zn, and Pb on microbial activity, and growth in calcareous soils. Soil samples were treated with increasing concentrations of Cu, Zn and Pb and subjected to short term and long-term incubations. Following the short- and long-term incubations the soil’s urease, arginase, and dehydrogenase activities together with the respiration rate were determined. Following the long-term incubation microbial growth was also investigated. From the overall findings, Cu exerted the most negative effects on both enzymatic activity and respiration rates, with continuously persisting effects on activity and respiration occurring the longer it remained in the soil matrix. To an extent Zn also exerted some negative effects on the soil, however these effects were more dependent on the type of enzyme being observed as well as the level of concentration incorporated. Indeed, enzymatic activity and microbial respiration were unresponsive to Pb, following prolonged exposure to this metal contaminant. However, under the short-term incubation, Pb did exert a negative effect on urease activity and to a lesser extent arginase, when higher concentrations were applied. In, terms of microbial plate growth, all treatments displayed no negative correlations and/or limitations of growth, regardless of concentration or the nature of the metal. In fact, in the case of Zn contamination an increase in microbial growth was noted with an increase in concentration. These findings might imply that microorganisms do in fact, have the ability to adapt to the altered soil conditions or indeed in some instances flourish. Description: M.Sc.(Melit.)

2024-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/126758 2024-11-11T12:31:33Z 2024-01-01T00:00:00Z

Title: The last wild grazer : exploring habitat preferences of oryctolagus cuniculus in the Maltese garrigue Abstract: The European rabbit (Oryctolagus cuniculus, Linnaeus 1758) is the only remaining wild mammal herbivore in Malta, where it has been introduced during Antiquity. The species poses a global conservation paradox, being endangered in its native range but highly invasive elsewhere, in particular on islands. While Malta shares some characteristics with its native habitats, the ecology of the rabbit has never been assessed locally. This study aimed to assess the reality of this paradox in the Maltese context by quantifying the effect of selected habitat parameters of known importance to the rabbit in its native semi-arid ecosystems. A total of 24 sites (1ha each) were surveyed by integrating high-resolution drone imagery and national LiDAR data through supervised SVM classification (kappa = 0.83), along systematic quadrat surveys to measure pellet density. Analysis was performed using separate Generalized Linear Models relating pellet counts with shrub vegetation’s structure (number of shrubs, shrub height and area, aggregation), intra-site land cover composition, and the surface of three anthropogenic features in and around sites (paved roads, hiking trails and rubbles walls), respectively. The extent of paved roads and hiking trails were both negatively correlated to pellet counts and explained together 48% of the variations in pellets across sites. The land cover composition could explain only 26% of the variations in pellets, while the ratio of herbaceous to low-lying shrubs was identified as the main driver negatively correlated to pellet density (marginal R2=0.24). Lastly, the measured shrub metrics did not show significant effects on pellet counts. The findings of this study confirmed the predominant role of human development in Malta for the spatial distribution of the wild rabbit in the remaining open semi-natural habitats. Moreover, it highlighted that human hunting pressure is likely stronger than non-human predation pressure locally. Finally, a key role of the rabbit in the competition between herbaceous and dwarf shrub species in the Maltese garrigue was suggested. These findings have the potential to inform both ecological restoration projects and wild rabbit management in Malta. Description: M.Sc.(Melit.)

2024-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/126757 2024-09-23T06:20:56Z 2024-01-01T00:00:00Z

Title: At a snail’s pace : suitability of cornu aspersum and theba pisana as bioindicators for heavy metals in Malta Abstract: Heavy metals are a cause for great concern in the environment due to their toxic and bioaccumulative effects and therefore monitoring their prevalence is considered greatly important. One way of doing this is by using a bioindicator such as terrestrial snails. This study set out to determine the suitability of both the soft part and the shell of two snail species Cornu aspersum and Theba pisana, for monitoring the heavy metals arsenic (As), zinc (Zn), cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), chromium (Cr), aluminium (Al), manganese (Mn), barium (Ba), and vanadium (V) in Malta. Snails were sampled from various environmental situations from around Malta, acid digested, and analysed using MP-AES to identify and quantify the selected heavy metals. It was determined through ordination plots that individual samples had enough variation to constitute calling them effective bioindicators and that there was significant variation between shell and soft part samples. PERMANOVA tests showed statistically significant differences between the soft parts of the two species, with T. pisana soft parts being found to be the better bioindicator for arsenic (p=0.046), cadmium (0.032), nickel (0.008), lead (0.012), chromium (0.007), and aluminium (0.014). The soft parts of C. aspersum were shown to be the most effective bioindicator for barium (0.004). In the case of vanadium, it was only detected in shell samples, meaning that shells (especially those of T. pisana) must be used as bioindicators for this metal, making it the only time analysing shells was preferential to soft parts. For zinc, copper, manganese, and vanadium there was no statistically significant difference between the two species. The most abundant metals found in T. pisana was Arsenic > Cadmium > Chromium, while in C. aspersum this was Arsenic > Cadmium > Barium. Description: M.Sc.(Melit.)

2024-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/126756 2024-09-23T06:09:55Z 2024-01-01T00:00:00Z

Title: Environmental linkages between the Salini salt pans and the marine system Abstract: The Salini saltworks, Malta's most extensive salt production facility, originally a natural wetland, now serves as a nature reserve. Oriented along a northeast-southwest axis, the salina spans 740 meters in length and 140 meters in width, covering an area of 90,000 m2. It consists of two large seaward-facing reservoirs, each with an area of 12,000 m2, and 33 smaller inland pans, whose areas range between 900 and 2,000 m2. Prior research has often focused on specific taxa, predominantly birds, or examined the salina in isolation, neglecting the influence of surrounding marine conditions. This study seeks to bridge this gap by examining the salina's abiotic and biological trends and their connection to marine environments. Through monthly visits from July 2022 to July 2023, measurements were taken of water temperature, pH, electrical conductivity, and nitrate and phosphate levels from the sea to the pans. The diversity of macroalgae, spermatophytes, and macroscopic fauna was assessed via direct observations, collections, and automated photography. Findings revealed that water quality within the salina varied both spatially and temporally, displaying a pronounced abiotic gradient from the sea toward the landward pans, indicating significant shifts in water characteristics during its transit. Electrical conductivity, for example, increased from approximately 50 mS cm-1 in the marine environment to about 60 mS cm-1 in the reservoirs, and up to 200 mS cm-1 in the most inland pans. This pattern was statistically significant and more pronounced during the dry season when conductivity, nitrate, and phosphate concentrations peaked. Variations in water pH, nitrate, and phosphate levels exhibited no clear spatial trends but were influenced by seasonal changes. The extreme conditions in the innermost pans during the dry season included hypersaline waters and water temperatures sometimes exceeding 40°C. An ecological gradient was also observed, with species richness escalating in the reservoirs compared to the marine environment and decreasing significantly in the inner pans. The enhanced biodiversity in the reservoirs can be attributed to their relative stability in mechanical energy and physico-chemical conditions compared to the fluctuating marine environment and the extreme conditions in the pans. These reservoirs harboured a diverse array of life forms, including four spermatophyte species, numerous macroalgae taxa, and a wide variety of macroscopic fauna, while the more distal pans showed a stark decline in biodiversity, hosting only a few adapted species such as the Dunaliella salina. Environmental linkages between the Salini salt pans and the marine system Additionally, this research identified the Atlantic Blue Crab's presence and noted the colonisation of the reservoirs by the Upside-Down Jellyfish. Ultimately, this study accentuates the necessity of integrating internal and external environmental factors in managing the habitat, especially focusing on preserving the biodiversity-rich reservoirs within the Salini saltworks complex. Description: M.Sc.(Melit.)

2024-01-01T00:00:00Z