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We present and discuss temperatures, major and trace element gas geochemistry, radiogenic isotopes (Pb, Sr) and the first Zn isotope data of fumarole condensates and altered rocks from the Vulcano fumarolic field. The fumaroles of the La Fossa cone, sampled on 5th May 2015, have temperatures ranging between 233 and 427 °C. They plot compositionally on the mixing trend between the magmatic and hydrothermal end-members defined by previous studies, but are strongly displaced towards the hydrothermal component. Correlations of radiogenic (Sr, Pb) and stable isotopes of Zn with δ13CCO2 and several trace elements of the fumarolic acid condensates support mixing between the above mentioned distinct (magmatic and hydrothermal) fluids. The magmatic end-member has a less radiogenic Sr (87Sr/86Sr ~0.7045) and heavier Zn isotope composition (δ66Zn ~0.3‰). The hydrothermal fluid end-member has a more radiogenic 87Sr/86Sr signature (>0.7055), which could be due to leaching of radiogenic Sr from the crystalline basement rocks or reflect seawater Sr. It is also characterized by lighter Zn isotope composition (δ66Zn < −0.3), most likely reflecting equilibrium fractionation of Zn isotopes during precipitation of sphalerite (ZnS) from the hydrothermal fluid. Nonetheless, some scatter in the correlation trends suggests either the involvement of additional (subordinate) source(s) or temporal variations in isotopic and chemical compositions of the two above end-members. Pb isotope compositions of the fumaroles sampled in this study show a shift towards less radiogenic values compared to pre-2001 fumaroles. This could indicate either a change in the hydrothermal circulation pattern (leading to leaching of rocks with different isotopic compositions) or the involvement of a new, isotopically distinct, magmatic fluid. The alteration zones around the fumarole vents are also characterized by systematic correlations of Pb and Zn isotopes with major and trace elements. We interpret these as the result of the addition onto the substratum volcanic rock of Pb and Zn from the fumaroles. Zn isotope signatures of the alteration zones are significantly heavier than those of the corresponding fumaroles (δ66Zn = 0.3–1.6) probably due to equilibrium fractionation occurring during sphalerite precipitation at the vent discharge.

International audience; Basaltic magmas can transport and release large amounts of volatiles into the atmosphere, especially in subduction zones, where slab-derived fluids enrich the mantle wedge. Depending on magma volatile content, basaltic volcanoes thus display a wide spectrum of eruptive styles, from common Strombolian-type activity to Plinian events. Mt. Etna, in Sicily, is a typical basaltic volcano where the volatile control on such a variable activity can be investigated. Based on a melt inclusion study in products from Strombolian or lava-fountain activity to Plinian eruptions, here we show that for the same initial volatile content, different eruptive styles reflect variable degassing paths throughout the composite Etnean plumbing system. The combined influence of i) crystallization, ii) deep degassing and iii) CO2 gas fluxing can explain the evolution of H2O, CO2, S and Cl in products from such a spectrum of activity. Deep crystallization produces the CO2-rich gas fluxing the upward magma portions, which will become buoyant and easily mobilized in small gas-rich batches stored within the plumbing system. When reaching gas-dominated conditions (i.e., a gas/melt mass ratio of ~ 0.3 and CO2,gas/H2Ogas molar ratio ~ 5), magma batches will erupt effusively or mildly explosively. In case of the 122 BC Plinian eruption, open-system degassing conditions took place within the plumbing system, such that earlier CO2-fluxing determined gas accumulation on top of the magmatic system, likely followed by H2O-fluxing further hydrating the shallow magma. The emission of such a cap in the early eruptive phase triggered the arrival of deep H2O-rich magma whose fast decompression and bubble nucleation led to the highly explosive character, enhanced by abundant microlite crystallization and consequent increase of magma effective viscosity. This could explain why open system basaltic systems like Etna may experience highly explosive or even Plinian episodes during eruptions that start with effusive to mildly explosive phases. The proposed mechanism also determines a depression of chlorine contents in CO2-fluxed (and less explosive) magmas with respect to those feeding Plinian events like 122 BC. The opposite is seen for sulfur: low to mild-explosive fluxed magmas are S-enriched, whereas the 122 BC Plinian products are relatively S-poor, likely because of early sulfide separation accompanying magma crystallization. The proposed mechanism involving CO2 separation and fluxing may suggest a subordinate role for variable mixing of different sources having different degrees of K-enrichment. However, such a mechanism requires further experimental studies about the effects on S and Cl dissolution and does not exclude self-mixing between degassed and undegassed parcels within the Etna plumbing system. Finally, our findings may represent a new interpretative tool for the geochemical and petrologic monitoring of plume gas discharges and melt inclusions, and allow tracking the switch from mild-explosive to highly explosive or even Plinian events at Etna.

International audience; Volcanogenic halogens, in particular bromine, potentially play an important role in the ozone depletion of the atmosphere. Understanding bromine behaviour in magmas is therefore crucial to properly evaluate the contribution of volcanic eruptions to atmospheric chemistry and their environmental impact. To date, bromine partitioning between silicate melts and the gas phase is very poorly constrained, with the only relevant experimental studies limited to investigation of synthetic melt with silicic compositions. In this study, fluid/melt partitioning experiments were performed using natural silicate glasses with mafic, intermediate and silicic compositions. For each composition, experiments were run with various Br contents in the initial fluid (H2O–NaBr), at T–P conditions representative of shallow magmatic reservoirs in volcanic arc contexts (100–200 MPa, 900–1200 °C). The resulting fluid/melt partition coefficients (DBrf/m) are: 5.0 ± 0.3 at 1200 °C–100 MPa for the basalt, 9.1 ± 0.6 at 1060 °C–200 MPa for the andesite and 20.2 ± 1.2 at 900 °C–200 MPa for the rhyodacite. Our experiments show that DBrf/m increases with increasing SiO2 content of the melt (as for chlorine) and suggest that it is also sensitive to melt temperature (increase of DBrf/m with decreasing temperature). We develop a simple model to predict the S–Cl–Br degassing behaviour in mafic systems, which accounts for the variability of S–Cl–Br compositions of volcanic gases from Etna and other mafic systems, and shows that coexisting magmatic gas and melt evolve from S-rich to Cl–Br enriched (relative to S) upon increasing degree of degassing. We also report first Br contents for melt inclusions from Etna, Stromboli, Merapi and Santorini eruptions and calculate the mass of bromine available in the magma reservoir prior to the eruptions under consideration. The discrepancy that we highlight between the mass of Br in the co-existing melt and fluid prior to the Merapi 2010 eruption (433 and 73 tons, respectively) and the lack of observed BrO (from space) hints at the need to investigate further Br speciation in ‘ash-rich’ volcanic plumes. Overall, our results suggest that the Br yield into the atmosphere of cold and silicic magmas will be much larger than that from hotter and more mafic magmas.

Co-auteur étranger; International audience; Located on Halmahera island, Dukono is among the least known volcanoes in Indonesia. A compilation of the rare available reports indicates that this remote and hardly accessible volcano has been regularly in eruption since 1933, and has undergone nearly continuous eruptive manifestation over the last decade. The first study of its gas emissions, presented in this work, highlights a huge magmatic volatile contribution into the atmosphere, with an estimated annual output of about 290 kt of SO2, 5000 kt of H2O, 88 kt of CO2, 5 kt of H2S and 7 kt of H2. Assuming these figures are representative of the long-term continuous eruptive activity, then Dukono is the current most prominent volcanic gas discharge point in Indonesia and ranks among the top-ten volcanic SO2 sources on earth. Combining our findings with other recent volcanic SO2 flux results, obtained during periodic campaigns at a number of volcanoes with DOAS and UV-Cameras, the SO2 emission budget for Indonesia is estimated at 540 kt yr-1 , representing 2-3% of the global volcanic SO2 contribution into the atmosphere. This figure should be considered as minimum as gas emissions from numerous other active volcanoes in Indonesia are yet to be evaluated. This voluminous degassing output from Dukono is sustained by a depleted Indian-MORB (I-MORB) mantle source. This latter is currently undergoing lateral pressure from the steepening of the subducted slab, the downward force from the Philippine Sea plate and the westward motion of a continental fragments along the Sorong fault, leading to high fluid fluxes to the surface. Over the course of Dukono eruptive activity, the magma reservoir has changed from a less differentiated source that fed the past voluminous lava flows to a more evolved melt that sustained the current 5 10 15 20 25 Bani et al. Dukono degassing ongoing explosive activity.

Κατά την περίοδο 2004 με 2017, συλλέχθηκαν περισσότερα από 350 δείγματα ελεύθερων και διαλελυμένων αερίων στην Ελλάδα. Μαζί με αυτά συνυπολογίστηκαν και βιβλιογραφικά δεδομένα. Για καλύτερη κατανόηση της μελέτης, η χώρα διαιρέθηκε σε τέσσερις γεωλογικές ενότητες (Εξωτερικές [EH] και Εσωτερικές [IH] Ελληνίδες, Ελληνική Ενδοχώρα [HH] και ενεργό ηφαιστειακό τόξο [VA]) και με βάση τον συγκεκριμένο διαχωρισμό ερευνήθηκε η πιθανή σχέση της κύριας γεωχημικής σύστασης των αερίων με τα διάφορα γεωλογικά και γεωδυναμικά καθεστώτα των περιοχών δειγματοληψίας. Τα δείγματα αναλύθηκαν για την χημική (O2, N2, CH4, CO2, He, Ne, Ar, H2, H2S και C2-C6 υδρογονάνθρακες) και ισοτοπική τους (R/RA, δ13C-CO2, δ13C-CH4 and δ2H-CH4) σύσταση. Οι συγκεντρώσεις κυμαίνονταν από 0.10 έως 3370 μmol/mol για το He, 600 έως 995,000 μmol/mol για το N2, 0.60 έως 915,000 μmol/mol για το CH4 και 17 έως 1,000,000 μmol/mol για το CO2, ενώ οι ισοτοπικές τους τιμές από 0.01 έως 7.10 R/RA, -29.91 έως +6.00 vs. V-PDB για το δ13C-CO2, -79.8 έως +45.0‰ vs. V-PDB για το δ13C-CH4 και -311 έως +301‰ vs. V-SMOW για το δ2H-CH4. Λαμβάνοντας υπ’όψιν τις τιμές των R/RA και 4He/20Ne, υπολογίστηκε η συνεισφορά της ατμόσφαιρας, του μανδύα και του φλοιού για το He. Η μεγαλύτερη μανδυακή συνεισφορά (έως και 90%) βρέθηκε στο VA, ενώ η χαμηλότερη (0-20%) στο EH. Η συνεισφορά της ατμόσφαιρας ήταν σχετικά αμελητέα. Σύμφωνα με την γεωγραφική κατανομή των αερίων, είναι εμφανές πως το R/RA αυξάνεται σε περιοχές που χαρακτηρίζονται από: i) λεπτό φλοιό; ii) αυξημένες τιμές ροής θερμότητας; iii) πρόσφατη (Πλειστόκενο-Τεταρτογενής) ηφαιστειακή δραστηριότητα; και iv) τοπικά εκτατικά ή διασταλτικά ρήγματα. Οι υψηλότερες τιμές βρέθηκαν κατά μήκος του VA και οι χαμηλότερες στις EH. Επιπλέον, με βάση τις τιμές των CO2/3He και δ13C-CO2, υπολογίστηκε η συνεισφορά των Ιζηματογενών, Μανδυακών και Ασβεστολιθικών end-members του CO2. Οι πλειοψηφία των δειγμάτων παρουσίασε μία κυρίως ασβεστολιθική σύσταση για τον C, ενώ μόνο λίγα δείγματα έδειξαν μανδυακή σύσταση. Παρ’όλα αυτά, με τα υπάρχοντα δεδομένα, είναι αδύνατος ο διαχωρισμός του CO2 που προέρχεται από τους ασβεστολίθους του φλοιού και από εκείνους της υπό βύθισης πλάκας. Επί προσθέτως, λόγω της σύνθετης γεωδυναμικής ιστορίας, η ισοτοπική σύσταση του μανδυακού C θα μπορούσε να είναι επηρεασμένη από μετασωμάτωση συσχετιζόμενη με την βύθιση της πλάκας, όπως συμβαίνει και στην γειτνιακή περιοχή της Ιταλίας, κάνοντας την ισοτοπική του σύσταση πιο θετική. Σε τέτοια περίπτωση, η συνεισφορά του μανδύα θεωρείται ότι έχει υποτιμηθεί. Κάποια δείγματα παραθέτουν πολύ χαμηλες τιμές CO2/3He και δ13CO2 λόγω απώλειας του CO2, η οποία έχει προκληθεί είτε από διάλυση του CO2 σε υπόγεια νερά μικρού βάθους είτε από την καθίζηση του ασβεστίτη που λαμβάνει μέρος στε ορισμένες θερμές πηγές. Από την άλλη μεριά, οι τιμές του CH4/(C2H6+C3H8) (από 1.5 έως 93,200) σε συνδιασμό με τα ισοτοπικά χαρακτηριστικά του CH4, συνιστούν πως οι ελαφριές αλκάνες προέρχονται από διαφορετική αρχική πηγή και αρκετές φορές επηρεάζονται από δευτερογενή διαδικασίες. Στα αέρια των EH παρατηρείται μια σχετικά αποκλειστική βιοτική, κυρίως μικροβιακή, προέλευση για το CH4. Τα αέρια των ψυχρών πηγών των IH έχουν κυρίως θερμογενή προέλευση, αν και κάποια από αυτά συνδέονται με ηπειρωτικές σερπεντινιώσεις και μοιάζει να έχουν αβιοτική προέλευση. Το CH4 στις θερμές πηγές των IH, HH and VA και στα φουμαρολικά αέρια του VA φαίνεται να είναι κυρίως αβιοτικό, αν και τα χημικά και ισοτοπικά χαρακτηριστικά του μοιάζει να έχουν επηρεαστεί από δευτερογενή οξείδωση του CH4 θερμογενούς προέλευσης. Τέλος, κάποια από τα δείγματα παρουσιάζουν αρκετά θετικές ισοτοπικές τιμές (δ13C-CH4 έως +45.0‰ vs. V-PDB και δ2H-CH4 έως +301‰ vs. V-SMOW) πιθανότατα λόγω οξείδωσής τους από μικρόβια. In the period from 2004 to 2017, more than 350 samples of free and dissolved gases were collected along the whole Hellenic area. Some literature data have also been taken into consideration. For a better comprehension of this study, Greece was subdivided in four geologic units (External [EH], Internal [IH] Hellenides, Hellenic Hinterland [HH] and active Volcanic Arc [VA]) and based on that division, I investigate the possible relationship of the main geochemical composition of the gases with the different geological and geodynamical settings of the sampling sites. Samples have been analysed for their chemical (O2, N2, CH4, CO2, He, Ne, Ar, H2, H2S and C2-C6 hydrocarbons) and isotope (R/RA, δ13C-CO2, δ13C-CH4 and δ2H-CH4) composition. The concentrations range from 0.10 to 3370 μmol/mol for He, 600 to 995,000 μmol/mol for N2, 0.60 to 915,000 μmol/mol for CH4 and 17 to 1,000,000 μmol/mol for CO2, whereas the isotope values range from 0.01 to 7.10 for R/RA, -29.91 to +6.00 vs. V-PDB for δ13C-CO2, -79.8 to +45.0‰ vs. V-PDB for δ13C-CH4 and -311 to +301‰ vs. V-SMOW for δ2H-CH4. Considering the R/RA and 4 He/20Ne ratios the atmospheric, mantle and crustal contributions for He have been calculated. The highest mantle contribution (up to 90%) is found in the VA, whereas the lowest in continental Greece (0-20%). Atmospheric contribution is mostly negligible. Taking into consideration the geographical distribution of the gases, it is evident that the R/RA increases in areas characterised by: i) thin crust; ii) elevated heat flow values; iii) recent (PleistoceneQuaternary) volcanic activity; and iv) deep routed extensional or transtensional regional faults. The highest values are therefore found along VA and the lowest in EH. Furthermore, based on the CO2/3He and δ13C-CO2 values, the contribution of Sediment, Mantle and Limestone endmembers for CO2 was determined. The majority of the collected samples present a prevailing limestone C component and only few samples have a prevailing mantle C component. However, with the present data, it is not possible to distinguish CO2 deriving from crustal and slab-related limestones. Additionally, due to the complex geodynamic history, the mantle C isotope composition could be affected by subduction-related metasomatism and, similarly to the nearby Italian area, the C isotope composition could be more positive. In this case, the mantle contribution is probably underestimated. Some samples display very low CO2/3He and δ13CO2 values due to the CO2 loss caused either by dissolution of CO2 in shallow groundwater or by the calcite precipitation that is taking place in most of the thermal springs. On the other hand, the CH4/(C2H6+C3H8) ratios (from 1.5 to 93,200) coupled with CH4 isotopic features, suggest the light alkanes derive from a different primary source and are sometimes affected by secondary processes. An almost exclusive biotic, mainly microbial, origin of CH4 can be attributed to EH gases. Cold gases at IH have mainly a thermogenic origin, although some gases connected to continental serpentinization may have an abiogenic origin. Methane in gases bubbling in thermal waters of IH, HH and VA and fumarolic gases of the VA seem to have a prevailing abiogenic origin, although their chemical and isotopic characteristics may have been produced by secondary oxidation of thermogenic CH4. Finally, in some of the sampled gases, the isotopic values are extremely positive (δ13C-CH4 up to +45.0‰ vs. V-PDB and δ2H-CH4 up to +301‰ vs. V-SMOW) most probably caused by microbial oxidation.

Sulfur is an important volatile component of magmas that presents different oxidation states, depending on the redox conditions and on the phase of occurrence: in silicate melts it is typically dissolved as S⁶⁺ and/or S²⁻ , in the gas phase it occurs principally as SO₂ (S⁴⁺ ) and H₂S (S²⁻). Mount Etna, in which magmatic redox conditions are poorly constrained, is used as a case study to investigate sulfur behavior in hydrous basaltic magmas during magma differentiation and degassing. This research integrates the study of natural olivine-hosted melt inclusions with an experimental study on S solubility in hydrous alkali basalts at magmatic conditions.Experimental results suggest the important control of ƒO₂ on the S abundance in Etnean hydrous magma and its partitioning between fluid and melt phases. Melt inclusions were entrapped at different depths inside the magmatic system (up to ~ 18 km, below crater level). They delineate a continuous differentiation trend, marked by fractional crystallization, from the picritic basalt (FS) toward the most evolved and degassed (2013) basalt. S content in Etnean melt is extremely variable and reaches 4150 ppm in the primitive melt inclusions. XANES Fe³⁺/ΣFe spectra in some glass inclusions, resulted in the generally decreasing of Fe³⁺/ΣFe ratios from the most primitive (FS) to the most evolved (2013) melts. MELTS software confirms that the Fe³⁺/ΣFe decrease is due principally to the melt differentiation process, enhanced to the S degassing at ƒO₂ < NNO+1. Magma reduction, in turn, induces the decrease of the sulfur solubility in the hydrous Etnean basalt, as well as of the sulfide saturation, and may constitute a possible enhancer of S exsolution, triggering the important S degassing observed in the last decades in Mt. Etna.; Le soufre est un composant volatil important des magmas qui présente différents états d'oxydation en fonction des conditions d’oxydoréduction et de la phase dans laquelle il se trouve : dans le liquide silicaté, il est typiquement dissous comme S⁶⁺ et/ou S²⁻ , dans la phase gazeuse il se trouve principalement comme SO₂ (S⁴⁺ ) et H₂S (S²⁻). L’Etna, pour lequel les conditions d’oxydoréduction sont faiblement contraintes, est utilisée comme cas d’étude pour examiner le comportement du soufre dans les magmas basaltiques hydratés pendant la différenciation et le dégazage. Cette recherche combine l'étude des inclusions vitreuses avec une étude expérimentale en conditions magmatiques sur la solubilité du S dans les basaltes alcalins hydratés.Les résultats expérimentaux suggèrent l’important contrôle de la ƒO₂ sur la teneur en S dans les magmas hydratés de l’Etna, et le partage du S entre les phases fluid and liquid. Les inclusions vitreuses ont été piégées à différentes profondeurs à l'intérieur du système magmatique. Elles décrivent une tendance continue de différenciation, marquée par une cristallisation fractionnée, à partir de la composition picritique (FS) vers le basalte plus récent dégazé (2013). Le contenu en S dans le liquide de l'Etna est extrêmement variable et atteint 4150 ppm dans les inclusions vitreuses les plus primitives. Les spectres XANES Fe³⁺/ΣFe des certaines inclusions vitreuses donnent des rapports Fe³⁺/ΣFe généralement décroissants à partir du liquide le plus primitif (FS) jusqu’au plus évolué (2013). Les simulations effectué par le logiciel MELTS confirme que la diminution du rapport Fe³⁺/ΣFe est principalement due au processus de différenciation magmatique, renforcé par le dégazage du S à ƒO₂ < NNO + 1. Cette réduction du magma provoque à son tour la diminution de la solubilité du S dans les basaltes hydratés de l’Etna, et peut constituer un éventuel activateur de l’exsolution du S, à l’origine de l’important dégazage du S observé au cours des dernières décennies à l’Etna.

Vermetid reefs are intertidal biogenic habitats created by a dense aggregation of mollusks, frequently cemented by calcareous algae, and are typical of sub-tropical and warm–temperate rocky shores. These bioconstructions are valuable key-habitats of the coastal zones, increasing their productivity and biological value. In the Mediterranean, the main vermetid reef builders belong to the genus Dendropoma and are associated to encrusting coralline red algae. These organisms are ecosystem engineers protected under international European Legislation, although vermetid reef conservation is limited by a lack of biological and ecological knowledge. The two-way interactions between biota and the physical environment have not been previously studied for these reefs, further limiting understanding of the ecological value and function of this habitat. Phases of the Dendropoma life cycle are also understudied, making the key-processes during the reef development unclear. In an integrated coastal zone management framework, all of this knowledge is fundamental to strengthen vermetid reef conservation and management in the Mediterranean. This thesis aims to further understanding of traits of the Dendropoma reef system, undertaking novel themes of research, and by using an interdisciplinary approach. The research project has two main goals: 1) To describe which contribution the reef provide in preserving rock substrate from physical alteration 2) To understand which cues may promote Dendropoma reef formation A set of laboratory and field experiments and observations has been used to fulfill these aims. The study was conducted in Sicily, central Mediterranean, where the main reef builder species is Dendropoma cristatum (Biondi, 1857), associated with the coralline algae Neogoniolithon brassica-florida (Harvey) Setchell & Mason 1943. In detail, topic 1 aims to describe the bio-protective role of the Dendropoma encrustation on the underneath rock substrate. Bioprotection is described as the contribution that biological layers give to the conservation of the substratum they colonize, by mediating the deteriorative action of other factors, such as physical, chemical and biological weathering. In this study, internal temperature variations and salt weathering have been considered as rock physical stressors that are particularly relevant in the coastal zone, and which may be mediated by the Dendropoma encrustation. Lab experiments and analysis have been employed to describe subsurface variations of temperature and salt content inside rock cores covered by live and dead vermetids vs bare rocks. The experiments have demonstrated that the Dendropoma encrustation exerts a control on the factors responsible for rock weathering. Topic 2 aims to detect which physical and biological factors may promote D. cristatum settlement and recruitment, with implications for the reef development.D. cristatum recruitment and settlement have been measured in the field and in different conditions. A seasonal pattern of recruitment has been described for the Sicilian species D. cristatum, and the hydrodynamic regime has been showed do not affect this pattern within a range of Km. Aside, at a small spatial scale (from mm to cm), biogenic surface have been shown to affect the settlement dynamics of the crawling larvae of Dendropoma cristatum, more than physical complexity of the substratum. In detail, biological cues provided by a layer of crustose coralline algae or by a microbial film, may positively affect settlement dynamic, indicating suitable site for larvae attachment and having an influence on the early stages of Dendropoma cristatum development. In conclusion, this research has contributed to the description of some ecological traits of the reef-builder Dendropomacristatumand provided a wider view of the two-way interactions between this ecosystem engineer and the surrounding physical and biological environment. Within the perspective to improve Dendropoma reef management at Mediterranean scale, the gaining of information about the ecological functioning and role of this coastal systems may provide a valuable contribution. Vermetid reefs are intertidal biogenic habitats created by a dense aggregation of mollusks, frequently cemented by calcareous algae, and are typical of sub-tropical and warm–temperate rocky shores. These bioconstructions are valuable key-habitats of the coastal zones, increasing their productivity and biological value. In the Mediterranean, the main vermetid reef builders belong to the genus Dendropoma and are associated to encrusting coralline red algae. These organisms are ecosystem engineers protected under international European Legislation, although vermetid reef conservation is limited by a lack of biological and ecological knowledge. The two-way interactions between biota and the physical environment have not been previously studied for these reefs, further limiting understanding of the ecological value and function of this habitat. Phases of the Dendropoma life cycle are also understudied, making the key-processes during the reef development unclear. In an integrated coastal zone management framework, all of this knowledge is fundamental to strengthen vermetid reef conservation and management in the Mediterranean. This thesis aims to further understanding of traits of the Dendropoma reef system, undertaking novel themes of research, and by using an interdisciplinary approach. The research project has two main goals: 1) To describe which contribution the reef provide in preserving rock substrate from physical alteration 2) To understand which cues may promote Dendropoma reef formation A set of laboratory and field experiments and observations has been used to fulfill these aims. The study was conducted in Sicily, central Mediterranean, where the main reef builder species is Dendropoma cristatum (Biondi, 1857), associated with the coralline algae Neogoniolithon brassica-florida (Harvey) Setchell & Mason 1943. In detail, topic 1 aims to describe the bio-protective role of the Dendropoma encrustation on the underneath rock substrate. Bioprotection is described as the contribution that biological layers give to the conservation of the substratum they colonize, by mediating the deteriorative action of other factors, such as physical, chemical and biological weathering. In this study, internal temperature variations and salt weathering have been considered as rock physical stressors that are particularly relevant in the coastal zone, and which may be mediated by the Dendropoma encrustation. Lab experiments and analysis have been employed to describe subsurface variations of temperature and salt content inside rock cores covered by live and dead vermetids vs bare rocks. The experiments have demonstrated that the Dendropoma encrustation exerts a control on the factors responsible for rock weathering. Topic 2 aims to detect which physical and biological factors may promote D. cristatum settlement and recruitment, with implications for the reef development.D. cristatum recruitment and settlement have been measured in the field and in different conditions. A seasonal pattern of recruitment has been described for the Sicilian species D. cristatum, and the hydrodynamic regime has been showed do not affect this pattern within a range of Km. Aside, at a small spatial scale (from mm to cm), biogenic surface have been shown to affect the settlement dynamics of the crawling larvae of Dendropoma cristatum, more than physical complexity of the substratum. In detail, biological cues provided by a layer of crustose coralline algae or by a microbial film, may positively affect settlement dynamic, indicating suitable site for larvae attachment and having an influence on the early stages of Dendropoma cristatum development. In conclusion, this research has contributed to the description of some ecological traits of the reef-builder Dendropomacristatumand provided a wider view of the two-way interactions between this ecosystem engineer and the surrounding physical and biological environment. Within the perspective to improve Dendropoma reef management at Mediterranean scale, the gaining of information about the ecological functioning and role of this coastal systems may provide a valuable contribution.

Gli effetti dell’acidificazione degli oceani a livello globale hanno richiamato l’attenzione degli scienziati su dei sistemi marini naturali quali i vent superficiali di CO₂. Si tratta di mesocosmi naturali, in quanto su piccole scale spaziali (anche di pochi metri) si osservano marcati gradienti di pH, dove poter testare ipotesi ecologiche dell’acidificazione delle acque marine. Obiettivo della tesi è studiare le risposte della popolazione ittica alla riduzione del pH in vent superficiali mediterranei utilizzando numerosi descrittori, quali la struttura di comunità, l’organizzazione trofica, le caratteristiche e la composizione chimica delle strutture carbonatiche. Inoltre poiché i vent sottomarini hanno effetti sulla concentrazione e biodisponibilità di numerosi elementi in traccia, alcuni dei quali tossici, altro obiettivo della tesi è valutare i livelli di contaminazione della fauna ittica, il bioaccumulo e la biomagnificazione. Tenendo in considerazione la mancanza di studi di questo tipo nei vent superficiali, i risultati di questa tesi contribuirebbero a colmare un gap conoscitivo di fondamentale importanza per capire e prevedere gli effetti ecologici dell’acidificazione a livello globale. Inoltre va sottolineato che la componente biologica indagata ha una rilevanza economica oltre che ecologica in quanto molti pesci sono specie target per la pesca e il loro consumo potrebbe avere effetti nocivi sulla salute umana. The “business-as-usual emission scenario” simulated by the IPCC (Intergovernmental Panel on Climate Change) suggests that atmospheric CO2 levels could approach 800 ppm by the end of the century. Corresponding biogeochemical models indicate that surface ocean water pH will drop from a pre-industrial value of about 8.2 to 7.8 within 2100 (Feely et al., 2010). This phenomenon known as "Ocean Acidification" (OA) is caused by the increasing CO2 emissions due to anthropic activities, with a current consequence decrease of about 0.1 unit of pH (Caldeira & Wickett 2003) that is having effects on seawater carbonate chemistry and on marine ecosystems. Many short-term laboratory experiments have shown the effects of OA on marine calcareous organisms (Doney et al., 2009), but also on not-calcifying ones. For instance, experiments on fish have revealed effects on physiological and behavioral aspects (Dixson et al., 2010; Munday et al., 2009), but many other aspects are still unknown (Ishimatsu et al., 2008). On the other hand, field experiments have been conducted in naturally acidified marine ecosystems, known as CO2 vents, which are currently investigated to study the long-term effects of OA on species, communities and ecological processes (Hall-Spencer et al. 2008). Shallow CO₂ vents are widespread in Mediterranean (Dando et al., 1999) and represent a sort of natural mesocosms, where marked pH gradients are present at small spatial scales. The aim of this PhD project is to assess the effect of high pCO2/low pH on the structural and functional organization of fish assemblages in a Mediterranean shallow CO₂ vent (Aeolian Archipelago, NE Sicily). In particular, we compare the responses of a chronic exposed fish assemblage living near the primary vent (mean pH = 7.8; hereafter “Low pH”) with other two fish assemblages living at normal pH (mean pH = 8.2; hereafter “Control 1” and “Control 2”) in Vulcano and Lipari Islands. We hypothesized that the organization of fish assemblage at the low pH site is different from that in controls. To test our hypothesis we use several descriptors and different methodologies. First, we compared fish community structure by using Underwater Visual Census technique to assess species richness and abundance (frequency of occurrence). Then we carried out samplings to evaluate trophic organization of fish assemblages (we used stable isotopes of carbon and nitrogen to analyze food web and trophic levels), bioaccumulation and biomagnification of trace elements (concentration and bio-availability of several trace elements, also toxic ones, may increase due to direct input from the vent and to peculiar pH and Eh conditions), reproduction success (we compared the gametic stage of some common fish species exposed to different pH levels through histological analysis on gonads) and the characteristics of carbonate structures like otoliths (to assess the effect of acidification on these structures by morphological analysis). Otoliths are also used as natural tags to study fish “habitat use” of this particular site through microchemistry analysis of trace elements and isotopic composition. Moreover, we carried out a manipulative experiment of Cymodocea nodosa shoots transplanting grew at different pH values to test the food choice of herbivores. The objective foreseen for the end of this PhD project is to provide a complete and exhaustive frame of fish assemblages’ organization at different pH levels, in a particular environment such as a CO2 vent. As scant information is available in the literature on this topic, the results of this research will provide information about the ecological effects of long-term exposures to high CO2 levels on fish, a key biological component whose monitoring is relevant not only from the ecological standpoint but also for the economic one and for the implications on human health.

During the reawaking of a volcano, magmas migrating through the shallow crust have to pass through hydrothermal fluids and rocks. The resulting magma–hydrothermal interactions are still poorly understood, which impairs the ability to interpret volcano monitoring signals and perform hazard assessments. Here we use the results of physical and volatile saturation models to demonstrate that magmatic volatiles released by decompressing magmas at a critical degassing pressure (CDP) can drive volcanic unrest towards a critical state. We show that, at the CDP, the abrupt and voluminous release of H2O-rich magmatic gases can heat hydrothermal fluids and rocks, triggering an accelerating deformation that can ultimately culminate in rock failure and eruption. We propose that magma could be approaching the CDP at Campi Flegrei, a volcano in the metropolitan area of Naples, one of the most densely inhabited areas in the world, and where accelerating deformation and heating are currently being observed., Magmas may migrate through hydrothermal fluids, but magma-hydrothermal interactions are poorly understood. Here, Chiodini et al. use physical and volatile models showing that at a critical degassing pressure the release of magmatic gases can heat hydrothermal fluids triggering deformation leading to eruption.

Il progetto di ricerca s’incentra sullo studio della macrofauna rinvenuta nel sito paleontologico e archeologico di Poggetti Vecchi, scoperto nella località di Roselle situata in provincia di Grosseto. Nello specifico esso è stato focalizzato sulla ricostruzione paleoambientale e paleoecologica dell’area. L’analisi paleobiologica e tafonomica dei resti faunistici è stata perciò inserita all’interno di un progetto multidisciplinare e l’integrazione di tutti i dati paleontologici (relativi a vertebrati, invertebrati, macroresti vegetali e pollini) con quelli stratigrafici ha permesso di ricostruire dettagliatamente l’evoluzione paleoambientale. Nella seconda parte, lo studio paleoecologico è stato completato dalle indagini sugli adattamenti paleodietetici acquisiti dalla popolazione di elefanti della specie Palaeoloxodon antiquus che caratterizza questo sito. Lo scavo, avvenuto nel corso del 2012, ha messo in luce il ritrovamento di un importante sito preistorico, con abbondanti resti di mammiferi associati a manufatti litici e lignei (digging sticks). Il sito è situato nella zona orientale della pianura prossimale grossetana. Questa vasta pianura costiera è circondata da rilievi bassi Triassico-neogenici costituiti da depositi clastici e carbonatici. Si tratta di un bacino lacustre-palustre di lungo corso, in cui lo spesso riempimento Quaternario è formato da sedimenti sabbiosi e fangosi. Il substrato carbonatico sottostante è soggetto a fenomeni di carsismo e alla formazione di numerosi sinkhole. L’area è inoltre caratterizzata da numerose risorgive termali, la fratturazione e la foliazione del bedrock favoriscono l’emergenza locale delle acque termali sotterranee. Lo studio geologico della successione ha evidenziato la presenza di sette unità litostratigrafiche (U1-U7). I resti di vertebrati e gli strumenti sono stati rinvenuti principalmente nell’unità 2, si tratta di una sezione formatasi in un momento di sedimentazione scarsa o nulla. La sovrastante unità 4 è caratterizzata dalle pisoliti, prodotte per accrezione durante processi di precipitazione biochimica in acque termali calme. Esse sono state sottoposte a datazione radiometrica con il metodo della serie dell’uranio, datando perciò l’unità a 171 ± 3 ka. Una seconda datazione pari a 170 ± 13 ka è stata condotta su un molare inferiore sinistro di Bos primigenius, proveniente dalla medesima unità, usando il metodo ESR. Alla luce di questi dati radiometrici, le evidenze umane del sito possono essere attribuite all’uomo di Neanderthal mentre, l’origine e l’evoluzione dell’intera successione sono avvenute nell’intervallo compreso tra l'ultimo interglaciale MIS7 e tutto il glaciale MIS6; un periodo caratterizzato da frequenti fluttuazioni climatiche. La macrofauna era dominata da erbivori di grande taglia: principalmente P. antiquus (almeno 7 individui) e B. primigenius. L’insieme dei dati tafonomici e paleobiologici raccolti ha permesso di formulare alcune ipotesi sull’origine dell’accumulo fossilifero. Il ritrovamento di resti faunistici e manufatti associati pone l’interrogativo sullo sfruttamento umano delle faune, in questo caso degli elefanti, per caccia attiva o come azione di sciacallaggio di animali già morti. Tuttavia, gli altri siti del Pleistocene medio che testimoniano la caccia attiva sono generalmente costituiti da un solo individuo di elefante (e.g., Ficoncella, Notarchirico, Southfleet Road, Ambrona). Al contrario, il ritrovamento di più individui costituisce normalmente accumuli time-averaged generati da trasporto fluviale (e.g., La Polledrara di Cecanibbio). Alla luce di queste considerazioni, appare evidente che gli elefanti di Poggetti Vecchi costituiscano un caso senza precedenti. Diverse caratteristiche concorrono a escludere un’azione di caccia attiva, ad esempio la struttura ontogenetica che suggerisce la presenza di un clan famigliare (giovani, subadulti, giovani-adulti e adulti), i contatti osso-osso (il sedimento interposto tra le ossa è scarso o nullo) e l’assenza di segni di taglio e fratture a osso fresco riconducibili ad attività di caccia. Queste evidenze suggeriscono che tutti gli individui siano morti pressoché nello stesso momento a causa di un evento naturale. L’ipotesi di un’azione di caccia attiva e dell’uccisione di un intero clan famigliare appare, inoltre, poco plausibile considerando le dimensioni raggiunte da questi animali (oltre 4 m di altezza) e la tecnologia disponibile. Tra le possibili cause naturali sono stati esclusi gli eventi alluvionali, poiché solo una grande alluvione avrebbe potuto trasportare e ridepositare animali di queste dimensioni e le tracce di abrasione e lucidatura dovute al ruscellamento, seppure presenti su alcuni esemplari, non sono tali da giustificare un simile scenario. Inoltre, è stata scartata anche l’ipotesi di una colata fangosa, poiché sono assenti i sedimenti fini che normalmente sono associati a depositi formatisi in seguito a questo tipo eventi. L’eventualità di degassamento naturale tossico è stata esclusa per almeno due motivi: l’attività termale stabile nell’area è successiva alla deposizione dell’unità 2 e, inoltre, è difficile ipotizzare la morte simultanea nello stesso luogo di individui diversi per età, dimensione corporea e sesso. Alla luce di tutte queste considerazioni è stato ipotizzato che un’ondata di freddo intenso, oltre i limiti di tolleranza termica, abbia determinato la morte degli elefanti. Questa specie era, infatti, tipica delle aree boscose durante le fasi temperate, mentre era rara negli interstadiali più lievi che intervallavano le fasi fredde o nelle condizioni fredde di una fase stadiale; infatti, la sua occorrenza può essere considerata un buon indicatore di condizioni interglaciali. Probabilmente, le condizioni climatiche avverse hanno confinato gli elefanti nelle immediate vicinanze dell’unica fonte di calore, ossia le pozze termali che caratterizzano l’area; poi, una volta esaurito il cibo disponibile, essi sono morti di fame. Gli strumenti litici associati alle ossa sono ritoccati e le tracce d’uso evidenziano l’azione su tessuti molli; quindi sembra plausibile che le popolazioni locali di neandertaliani abbiano avuto accesso a una grande quantità di carne messa loro a disposizione dalle circostanze fortunate. Nel complesso: il basso impatto dei carnivori (pochi segni di masticazione, rosicatura e corrosione gastrica), l’assenza di modificazioni di derivazione umana e la bassa incidenza dell’alterazione meteorica suggeriscono che le carcasse fossero in gran parte inaccessibili ai predatori perché presumibilmente parzialmente sommerse dall’acqua. I resti scheletrici non sono in connessione anatomica, ovunque sono evidenti graffi e scalfitture riconducibili al calpestio e fratturazione avvenuta allo stato secco. Calpestio e calci sembrano essere stati prodotti da altri grandi mammiferi, presumibilmente altri elefanti, che hanno determinato la dispersione dei resti. La frequentazione dei luoghi in cui sono morti altri individui della stessa popolazione e il conseguente calpestio e rimescolamento dei resti ossei è stato evidenziato e studiato anche nelle popolazioni attuali di elefanti. Tale comportamento sembra essere connesso al forte psichismo di questi animali. Infine, la selezione di ampie porzioni di carcassa degli elefanti indica che è avvenuta la rimozione di alcuni elementi ossei (vertebre, coste, basipodiali e falangi) che potrebbero essere stati rimossi facilmente dall’acqua quando le carcasse erano già scheletrizzate. Tuttavia, non può essere completamente esclusa la rimozione da parte degli scavengers (carnivori e uomini). Infine, il letto fossilifero è stato colonizzato dalle radici delle piante acquatiche o sepolto da sedimenti pedogenizzati. L’evoluzione paleoambientale durante la deposizione delle diverse unità stratigrafiche è stata dettagliatamente ricostruita integrando i dati paleontologici (relativi a vertebrati, invertebrati, macroresti vegetali e pollini) con quelli stratigrafici. In sintesi, sono stati identificati quattro diversi eventi alluvionali separati da fasi regressive ed erosive. Durante le fasi alluvionali, i fanghi organici con caratteristiche fisico-chimiche omogenei sono stati depositi sul fundo di un lago poco profondo durante le fasi alluvionali. Al contrario, i resti di vertebrati e gli artefatti umani sono stati accumulati sulle superfici erosive formatesi durante le regressioni. La prima fase alluvionale ha prodotto una baia lacustre-palustre caratterizzata da sedimentazione terrigena (U1). In questa fase il fondo del lago era popolato da molluschi e ostracodi indicatori di acque dolci o leggermente saline (< 4 psu). Il primo episodio di disseccamento ha prodotto la superficie erosiva tra U1/U2; esso è stato sufficientemente lungo e tale da consentire l’accumulo di resti di vertebrati e manufatti. Un nuovo innalzamento tavola d’acqua e la deposizione di fanghi carbonatici che testimoniano l’inizio della risorgenza termale (unità 3). La formazione del deposito pisolitico (unità 4) suggerisce la formazione, durante il tardo MIS6 di pozze termali analoghe a quelle adesso presenti nell’area. Esse erano frequentate dagli elefanti e dagli altri mammiferi. Una nuova caduta del livello lacustre ha determinato la re-incisione dell’impluvio e il riempimento con ghiaia poligenica e clasti calcarei (U5). In seguito, una nuova fase alluvionale ha favorito nuovamente la formazione di una baia lacustre-palustre caratterizzata da sedimenti terrigeni (U6). Poi, un nuovo evento di abbassamento della tavola d’acqua ha prodotto una nuova fase d’incisione del fondovalle e conseguente formazione di una nuova baia lacustre. Infine, la composizione carbonatica dei fanghi dell’unità 7, testimonia lo sviluppo di attività termale stabile nell’area. Durante le fasi regressive ed erosive il paesaggio era dominato da vaste praterie, boschi radi, corpi d’acqua poco profondi e aree umide formate dalla risalita di acqua sotterranea. La datazione radiometrica e la stratigrafia dei depositi transgressivi e regressivi hanno permesso di eseguire un tentativo di sincronizzare la successione sedimentaria e i principali eventi climatici quaternari. I depositi transgressivi dell’unità 1 potrebbero essere stati deposti durante il sub-stage temperato MIS7a o durante l’interstadiale successivo alla transizione con il MIS6 (tra 200-191 ka). La formazione della superficie erosiva (unità 2) risalirebbe perciò all’inizio del MIS6. Le unità 3 e 4 testimoniano la transgressione lacustre e l’attivazione del sistema termale durante il primo interstadiale del MIS6 (circa 170 ka). La nuova fase regressiva (unità 5) sarebbe così avvenuta durante lo stadiale successivo; mentre la nuova transgressione lacustre (unità 6) corrisponderebbe al secondo interstadiale. Infine, i depositi dell’unità 7 potrebbero risalire al miglioramento climatico il culminato con il picco dell’interglaciale MIS5e. L’analisi paleontologica ha evidenziato che nel complesso la fauna a micromammiferi è dominata da Arvicola amphibius, un tipico abitante degli ambienti umidi. Tuttavia, mentre nell’unità 6 sono presenti tipici taxa indicatori di habitat temperati (Crocidura cf. suaveolens, Oryctolagus sp. e Microtus (Terricola) savii), nell’unità 2 abbonda Microtus cf. arvalis che costituisce un chiaro indicatore di come muovendosi verso l’alto nel corso della successione, le temperature siano diminuite. Infatti, le popolazioni italiane moderne di M. cf. arvalis sono limitate alle regioni settentrionali della penisola e sono assenti dall'Appennino centrale. Pertanto, la presenza nell’area meridionale della Toscana a quote molto basse è indice di condizioni più fredde rispetto a quelle oggi esistenti. Inoltre, in quest’unità diminuisce l’abbondanza relativa di M. (Terricola) ex gr. savii e sono assenti Crocidura e Oryctolagus. La macrofauna e l’erpetofauna rinvenute nell’unità 2, sono costituite da taxa termofili che ben si adattano alle oscillazioni climatiche avvenute tra l’inizio del MIS7a (regressione lago ed erosione sommità di U1) e l’interstadiale successivo (regressione del lago e deposizione U3-4). Anche il record della fauna a molluschi è compatibile con la tendenza al raffreddamento culminata con il massimo glaciale del MIS6, così come le specie di ostracodi che indicano chiaramente temperature inferiori di 6°C rispetto a quelle attuali. Oscillazioni stagionali, talvolta molto intense, possono ragionevolmente aver interessato l’area nel corso dell’intera successione; ciò suggerisce che un’ondata di freddo intenso, nel corso del periodo in cui si è depositata l’unità 2, potrebbe aver portato allo stremo la famiglia di elefanti poi morti di stenti. In conclusione, il periodo umido registrato intorno a 171 ka, cui si riferisce la datazione radiometrica assoluta calcolata sulla base dei sedimenti e dei resti fossili dell’unità 4, potrebbe ragionevolmente corrispondere al primo interstadiale glaciale del MIS6. Gli studi di paleodieta nei proboscidati presentano intrinseche difficoltà logistiche che possono essere facilmente intuibili considerando la complessa anatomia dei molari (con struttura modulare), la morfologia funzionale (ossia la meccanica di masticazione che modella costantemente la superficie occlusale) e, infine, il peculiare meccanismo di sostituzione per scorrimento orizzontale. Altre difficoltà riguardano l’interpretazione degli adattamenti dietetici, soprattutto quando si utilizza un solo metodo analitico; perciò l’analisi paleodietetica della popolazione di elefanti di Poggetti Vecchi e le derivanti speculazioni sulla ricostruzione paleoambientale sono state eseguite con un approccio multiproxy. Esso è stato basato sulla valutazione incrociata dei dati prodotti da: 1) analisi delle micro-tracce (microwear) presenti sulla superficie dello smalto dentario mediante basso ingrandimento (LDM); 2) determinazione del contenuto isotopico (δ13C e δ18O) nella bioapatite (smalto) e relativo calcolo del contenuto isotopico della paleodieta (δ13Cdiet) e dell’acqua ambientale (δ18Ow); 3) mesowear e 4) valutazione della tessitura superficiale attraverso i criteri della rugosità 2D, la valutazione statistica della complessità superficiale (mediante il calcolo della dimensione frattale che descrive i pattern geometrici complessi sfruttando la geometria non-euclidea) e l’identificazione della direzionalità delle micro-tracce superficiali. Il campione analizzato è costituito da 15 denti molari e include denti inferiori, superiori, appartenenti ad individui di entrambi i sessi e diverse classi di età. Poiché lo smalto è un materiale riflettente, l’osservazione delle tracce di microwear e della tessitura superficiale è eseguita su superfici replicate, generalmente prodotte in resina epossidica. Per quanto riguarda la tecnica di microwear mediante basso ingrandimento (LDM), i calchi della regione centrale di ogni lamella funzionale sono analizzati mediante stereomicroscopio con ingrandimento a 40 e 100x e illuminazione unidirezionale esterna. Le osservazioni qualitative e quantitative sono state compiute su microfotografie, mediante l’ausilio del software di grafica vettoriale ImageJ. Il pattern di microwear ottenuto è omogeneo ed evidenzia l’assenza di sostanziali differenze fra i molari superiori e inferiori, nelle diverse classi d’età così come nei due sessi. Al contrario, una maggiore eterogeneità caratterizza le estremità (laterale e buccale) di ogni lamella. I dati emersi da quest’analisi confermano che le lamelle centrali (e in particolare la regione mediana dei loop funzionali) registrano in modo più efficiente il segnale dietetico. Le lamelle più intensamente danneggiate mostrano il maggior impatto dell’usura, confermando l’esistenza di una forte correlazione tra l’usura attrizionale e le frequenze/densità delle microusure. Il pattern di microwear, soprattutto nelle lamelle centrali, è dominato dalla presenza di graffi (sia grossolani sia fini) associati ad aree di micro-abrasione; mentre i buchi sono molto scarsi. I graffi più grossi e quelli incrociati sono più frequenti nella porzione mesiale (più usurata) e distale (meno usurata). I dati ottenuti suggeriscono l’adattamento a una dieta mista dominata dal pascolo. L’analisi isotopica è stata condotta su un singolo campione di smalto. Un frammento della lamella centrale di un dente molare è stato prelevato dalla porzione basale. Il campione di smalto è stato separato meccanicamente dalla dentina e dal cemento. Dopo essere stato finemente macinato, è stato prima sottoposto a diffrazione ai raggi x per verificarne l’integrità strutturale; infine, la composizione isotopica (carbonio e ossigeno) del carbonato strutturale della bioapatite è stata analizzata allo spettrometro di massa. I valori del δ13C e δ18O ottenuti suggeriscono che nel momento di formazione dei livelli fossiliferi, la valle di Poggetti Vecchi era dominata da praterie boscose e condizioni climatiche freddo-umide. Gli attuali elefanti della savana africana hanno acquisito adattamenti alimentari da pascolatori e, soprattutto, nei periodi più umidi aumentano la quantità di erba ingerita; mentre in condizioni di maggiore aridità (quando l’erba declina) cambiano opportunisticamente abitudini alimentari prediligendo il consumo di foglie e arbusti (acquisendo perciò adattamenti alimentari tipici dei brucatori). I dati isotopici e il pattern di microwear confermano che un simile comportamento caratterizzava anche le specie estinte. Due campioni rappresentativi della popolazione, un cucciolo e un individuo adulto, sono stati selezionati per eseguire la caratterizzazione della tessitura superficiale. I calchi delle lamelle centrali sono stati quindi scansionati con un microscopio digitale a 500x in grado di generare immagini 3D componendo una serie di piani presi a vari livelli. Varie aree d’interesse sono state selezionate dalla porzione centrale delle lamelle di smalto mediane. Le foto sono state poi processate con i software MountainsMap® e ImageJ. I vari strumenti presenti nel primo software hanno permesso di ottenere immagini 2D e di estrarre 10 profili di rugosità 2D per ogni area selezionata; così come di calcolare alcuni parametri di rugosità industriale 2D (secondo lo standard ISO 4287) utili nel discriminare il comportamento alimentare. Il calcolo della dimensione frattale (Df), ha fornito una stima della complessità superficiale, mentre l’orientamento delle caratteristiche tessiturali (espresso come percentuale d’isotropia e direzioni dominanti, in gradi) è espresso graficamente da un diagramma polare. Infine, sono state ricostruite le immagini 3D delle superfici di smalto montando i singoli profili bidimensionali. I risultati emersi da questa procedura sembrano confermare il pattern di microwear emerso dall’analisi a basso ingrandimento; suggerendo, inoltre l’assenza di distribuzione marcatamente anisotropa delle micro-scalfitture e tessitura superficiale generalmente complessa. Tutti gli indizi raccolti dall’analisi multiproxy avvalorano l’ipotesi che questa specie di elefanti avesse un comportamento alimentare non specializzato di tipo intermedio, basato sul pascolo di un notevole quantitativo di piante ricche di fitoliti, quali le graminacee. Infine, le misure di mesowear, sebbene concordino nell’individuare l’adattamento a una dieta mista, suggeriscono un comportamento più spiccatamente da brucatore. La discordanza nei risultati, emersi da microwear e mesowear, potrebbe essere spiegata considerando le differenze nella risoluzione temporale dei due metodi. Infatti, l’analisi di microwear rivela il comportamento alimentare negli ultimi giorni della vita dell'animale, mentre il mesowear registra i segnali alimentari corrispondenti a un periodo più lungo, dagli ultimi mesi di vita fino a qualche anno prima della morte. Inoltre, poiché P. antiquus cambiava opportunisticamente comportamento alimentare secondo le diverse condizioni ambientali locali, è plausibile pensare che le misure di mesowear catturino anche le possibili variazioni dietetiche stagionali. Tuttavia, così come per altre specie di proboscidati, anche l’elefante dalle zanne dritte era prevalentemente un pascolatore negli ambienti aperti e dominati dall’erba. Le misure di mesowear ottenute potrebbero così indicare anche lo spostamento degli elefanti da altre aree (e.g., quelle limitrofe), in cui il paesaggio era invece dominato da boschi, verso la vallata. Alla luce di queste considerazioni, la ricostruzione paleoambientale emersa dall’analisi mediante l’approccio geoarcheologico sembra essere confermata anche dal pattern di microwear. Le evidenze paleobiologiche e tafonomiche che suggeriscono il confinamento degli elefanti in un’area ben limitata, l’impossibilità di lasciare la valle con conseguente consumo di tutto il cibo presente nelle immediate vicinanze delle pozze termali e, infine, la morte per stenti, sembrano trovare riscontro nel segnale dietetico degli ultimi pasti che tipicamente descrive il pascolo di erbe e graminacee che dominavano la vallata di Poggetti Vecchi. Poggetti Vecchi is an open air archeo-paleontological site located on the eastern side of Grosseto’s plain, in Southern Tuscany (Italy). Excavation for the construction of thermal pools exposed an up to 3-meter-thick succession composed of seven lithostratigraphic units of terrigenous and carbonate sediments. Vertebrate bones mixed up with stone tools and wooden implements were discovered mainly in the lower portion of the succession (Unit 2). Thermal carbonates overlying these remains are radiometrically dated to 171 ± 3 ka. Based on this dating the human artifacts can be assigned to early Neanderthals, which sparks the interest in the site, especially from a geoarcheological perspective. In fact, it provides invaluable information not only on the local environmental conditions at time, but also on the interactions that humans had with the surrounding environment and natural resources. Poggetti Vecchi’s macrofaunal assemblage is dominated by large-sized herbivorous, i.e. the straight-tusked elephant and aurochs. Paleobiological inferences indicate the presence of at least seven elephants of different ontogenetic ages and sexes, which were likely the members of a family clan. Our geoarcheological study suggests that the assemblage accumulated in a narrow lacustrine-palustrine embayment, affected by thermal springs and surrounded by extensive open grassland environments. Rapid climatic fluctuations that occurred at the MIS7-6 transition and throughout the MIS6 glacial period caused changes in the lake level and the entire area was repeatedly flooded and exposed to subaerial erosion. During a period of global climate deterioration, the hot thermal springs probably created an attractive recess for the resident faunas and, perhaps, a cold snap during a time of intense seasonal oscillations led to the sudden death of elephants. The carcasses represented an unexpected food resource for the early Neanderthals that lived in this area. Environmental changes were studied in detail to contribute to the solution of paleoecology issues, with special focus on the paleodietary preferences of local population of elephants. This has been obtained by cross-comparing the results obtained by coupling different methods: low-magnification analysis of microwear (LDM), 2D-roughness parameters and surface geometry assessment (fractal dimensions and isotropy calculations), mesowear and stable isotope analysis. Proboscideans are super keystone species in their ecosystems. They therefore tend to be opportunists, able to feed with equal facility on a wide range of items available locally, whenever they cannot have access to their ideal diet. This improves elephants’ ability to respond to climate impacts and environmental fluctuations. Our analyses confirm that Palaeoloxodon antiquus was a generalized mixed-feeder, which is here believed to have been especially capable of shifting from its dietary preference according to local vegetation composition and seasonal changes. In particular, microwear patterns, isotopes and texture results suggest the consumption of a great amount of graminaee or other plants quite rich in phytoliths. The dietary signal of the last meals confirms the preliminary landscape reconstruction based on multiproxy approach. Conversely, mesowear data that indicate more browse-dominated mixed dietary behavior probably reflect seasonal variations, as well as the environmental scenario of other areas (e.g., the neighboring ones) characterized by more closed canopy woodland. On the whole this study proposes to infer the feeding habits of the group of late Middle Pleistocene individuals of Palaeoloxodon antiquus discovered in Poggetti Vecchi and, by doing so, to contribute to the interpretation of the site’s landscape at the time. Poggetti Vecchi offers us the fortunate chance to explore new instances of human-animal interaction at the Middle-Late Pleistocene transition, which is still very imperfectly known in Prehistoric Europe.

Microorganisms able to tolerate environmental extremes, or extremophiles, are ideal candidates to extend our knowledge on the limitations for terrestrial life, including sporicidal treatments, and on their ability to survive under conditions mimicking space environments. The spore resistance of bacilli isolated from extreme environments, cold (Antarctic soils) and hot (shallow hydrothermal vents of Eolian Islands, Italy), was evaluated towards environmental stressors (wet- and dry-heat, low and high pH values), sporicidal treatments and stresses simulating space-environments (UV-C and X-rays irradiations, desiccations by low pressure, exposition to oxidizing agents and low pressure plasma), as those from the planet surface of Europa (the satellite of Jupiter), Enceladus (the satellite of Saturn) and Mars. Spores from two thermophilic Eolian strains, Bacillus horneckiae SBP3 (SBP3) and B. licheniformis T14, and a psychrophilic Antarctic strain, B. simplex A43, were frequently the most resistant against simulating space conditions as UV-C, X-ray and heavy ions radiation. Despite belonging to the same species, spores from strains Bacillus horneckiae SBP3 and Bacillus horneckiae DSM 23175T responded differently to stresses, which may reflect the adaptation to harsh environmental conditions of the Eolian thermophilic strain. Additional comparisons were made with reference strains used in Astrobiology studies, isolated from spacecraft assembly facilities (B. horneckiae, B. nealsonii and B. pumilus SAFR032), and the biodosimetry strain and space microbiology model organisms B. subtilis 168. Spores of B. horneckiae SBP3 were able to survive stressing conditions (exposition to heat, acid and alkaline stresses, UV-C, X-rays, heavy ions, low pressure plasma, desiccation and hydrogen peroxide), often at higher degree than those of B. subtilis. The results obtained by Raman spectroscopy showed that the damages induced by heat stress to spores are related to the denaturation of proteins, rather than to those of nucleic acids. This finding suggests, that the mechanisms involved to contrast the heat stress are probably related to the thermostability of small-acid soluble proteins in spore-core. The resistance of spores to terrestrial environmental stressors could also be determinant in resisting to space stressors (as UV-C and X-rays radiations, exposure at temperature 95 and 130°C and desiccation stress). Moreover, exopolysaccharides structure and composition, involved in the biofilm formation, could be also considered as a mechanism to protect spores under stress conditions. As bacterial multi-resistant forms, the studied spores are expected to possess novel, unexplored applicative potentials in different contexts, such as new bio-indicators for safety and security in human activities, as well as in Astrobiology, in space exploration missions and “Planetary Protection” programs. Microorganisms able to tolerate environmental extremes, or extremophiles, are ideal candidates to extend our knowledge on the limitations for terrestrial life, including sporicidal treatments, and on their ability to survive under conditions mimicking space environments. The spore resistance of bacilli isolated from extreme environments, cold (Antarctic soils) and hot (shallow hydrothermal vents of Eolian Islands, Italy), was evaluated towards environmental stressors (wet- and dry-heat, low and high pH values), sporicidal treatments and stresses simulating space-environments (UV-C and X-rays irradiations, desiccations by low pressure, exposition to oxidizing agents and low pressure plasma), as those from the planet surface of Europa (the satellite of Jupiter), Enceladus (the satellite of Saturn) and Mars. Spores from two thermophilic Eolian strains, Bacillus horneckiae SBP3 (SBP3) and B. licheniformis T14, and a psychrophilic Antarctic strain, B. simplex A43, were frequently the most resistant against simulating space conditions as UV-C, X-ray and heavy ions radiation. Despite belonging to the same species, spores from strains Bacillus horneckiae SBP3 and Bacillus horneckiae DSM 23175T responded differently to stresses, which may reflect the adaptation to harsh environmental conditions of the Eolian thermophilic strain. Additional comparisons were made with reference strains used in Astrobiology studies, isolated from spacecraft assembly facilities (B. horneckiae, B. nealsonii and B. pumilus SAFR032), and the biodosimetry strain and space microbiology model organisms B. subtilis 168. Spores of B. horneckiae SBP3 were able to survive stressing conditions (exposition to heat, acid and alkaline stresses, UV-C, X-rays, heavy ions, low pressure plasma, desiccation and hydrogen peroxide), often at higher degree than those of B. subtilis. The results obtained by Raman spectroscopy showed that the damages induced by heat stress to spores are related to the denaturation of proteins, rather than to those of nucleic acids. This finding suggests, that the mechanisms involved to contrast the heat stress are probably related to the thermostability of small-acid soluble proteins in spore-core. The resistance of spores to terrestrial environmental stressors could also be determinant in resisting to space stressors (as UV-C and X-rays radiations, exposure at temperature 95 and 130°C and desiccation stress). Moreover, exopolysaccharides structure and composition, involved in the biofilm formation, could be also considered as a mechanism to protect spores under stress conditions. As bacterial multi-resistant forms, the studied spores are expected to possess novel, unexplored applicative potentials in different contexts, such as new bio-indicators for safety and security in human activities, as well as in Astrobiology, in space exploration missions and “Planetary Protection” programs.

Anthropogenic pressure on coastal ecosystems is vast and diverse, simultaneous impacts such as pollution, eutrophication and fishing pressure nowadays add up and interact with the effects of climate change (e.g., global warming, acidification and sea level rise). The magnitude of these effects on marine species and their replies can vary and the possible changes can depend on: i) species life-histories (LH) traits, ii) local environmental conditions and iii) contextual presence of more than one anthropogenic related stressor. The study of a single anthropogenic disturbance or Climate Change-derived alteration on multi-level ecological responses is misleading and generates unrealistic conclusions, and for this reason is actually recognized as the main limitation of the current ecosystem management approach. These climate change stressors exert negative effects on marine biota as single stressors, but at the same time they are also likely to have interactive effects on biodiversity and ecosystem functioning that are difficult to predict. Although the ecosystem based management (EBM) approach focuses on ecosystem equilibria, to provide realistic management measures for important activities at sea such as conservation, fisheries and aquaculture, there is a need of quantities. While ecological research has begun to document the individual effects of these various stressors on species and ecosystems, research into the cumulative and interactive impacts of multiple stressors is less frequent. This need is still cited as one of the most pressing questions in ecology and conservation. The effect of stressors on marine organisms has been frequently assessed using the Scope for Growth (SFG) approach, which lead to a static snapshot of the current physiological status of a target organism, used as an indicator of the ‘health’ of the ecosystem. In the last decade, eco-physiological studies have focused on linking the effect of climate change on species distributions based on organisms' physiological limits and, in some cases, with the overall relationship between environmental factors and physiological performance. In addition, past modelling efforts largely based on correlative Species Distribution Models (SDMs) also known as “bioclimatic envelope models”, “ecological niche models” or “habitat suitability models” used known occurrences of species across landscapes of interest to define sets of conditions under which species are likely to maintain populations. However, effective conservation management required models able to make projections beyond the range of available data. One way to deal with such an extrapolation is to use a mechanistic approach based on physiological processes underlying climate change effects on organisms. One such bio-energetic model, which has been successfully applied for modelling species distributions, is the Dynamic Energy Budget (DEB) model, which is able to deal with multiple stressors and other environmental parameters that are expected to affect the individual performance such as growth and reproduction. While Chapter 1 was dedicated to frame of general topic of the present thesis, Chapter 2 experimentally investigated the effects of a novel prey and a chronic increase in temperatures on functional traits and global fitness of the whelk Stramonita haemastoma. In Chapter 3, we applied a new approach using DEB models to investigate the effects of an anthropogenic pollutant on Life-History (LH) traits of marine organisms, providing stakeholders and policy makers an effective tool to evaluate the best environmental recovery strategy. In Chapter 4 we used DEB models to determine the effect of changing environmental conditions and pollution on the Indo-Pacific Perna viridis aquaculture. In Chapter 5 we proposed a DEB application to study the link between future COP21 predicted temperature scenarios and varying food availability on LH-traits of some Mediterranean fishery and aquaculture target species, exploring the efficiency of Integrated Multitrophic Aquaculture as a potential management solution. A spatial contextualization of model outcomes allowed translating those results into useful figurative representations. Through Chapter 6 we investigated the site-specific effects of environmental changes represented by Ocean Acidification and hypoxia on the functional and behavioural traits of the mussel Mytilus galloprovincialis. Finally, in Chapter 7 we presented a proof-of-concept study using the European anchovy as a model species to show how a trait-based, mechanistic species distribution model can be used to explore the vulnerability of marine species to environmental changes. Scenarios of temperature and food were crossed to generate quantitative maps of selected mechanistic model outcomes.

Biotic and abiotic factors synergistically act on natural systems. As a result ecological communities adjust their structural and functional responses to persist in a given area. Worldwide, marine ecosystems have been changing through time with increasing anthropogenic pressure in the last centuries leading to only 13.2% of the total marine environments in a ‘pristine’ state. The consequences of direct and indirect anthropogenic pressures may have on marine organisms can largely differ, with both negative and positive effects of drivers of change of human origin. In the span of three years for my PhD thesis, I performed different experiments with the main goal of examining how direct or indirect drivers of change may affect fish assemblages. For this purpose, I focussed on positive effects of protection activities within Marine Protected Areas (MPAs) in the Mediterranean Sea and potentially detrimental impacts of increasing CO2 concentrations in Italy, Japan, and Papua New Guinea. The first part of this thesis examined ecological responses within 11 Mediterranean Marine Protected Areas (MPAs) belonging to six different countries (France, Spain, Greece, Italy, Croatia, and Slovenia). I assessed whether and how MPAs can be successful in reaching their conservation goals (higher fish diversity and biomass than outside) and in re-establishing their trophic state (higher levels of top-down control inside their boundaries), despite differing management and protection schemes. Overall, results highlighted higher biomass levels both for whole fish assemblages and for commercial species targeted by small-scale and industrial fishery inside the 11 pilot MPAs. Overall predation rates were unaffected despite a few MPAs showing higher rates inside than outside their boundaries. The second part of this thesis tackled the direct and indirect effects of ocean acidification at an ecosystem level. Ecological surveys on both benthic habitat and fish assemblages were carried out in three different volcanic seeps belonging to diverse climatic zones in the Mediterranean and the Pacific ocean, with the main aim of assessing similar response trends. Chronical exposure to elevated CO2 levels did affect benthic communities in a direct way, indirectly modifying associated fish assemblages both in terms of diversity and relative abundances. Predation rates were similar among regions and within high CO2 and reference CO2 levels. Such findings support the hypothesis of unaltered food web dynamics under OA conditions despite community shifts and fish diversity changes, therefore contrasting with previous literature documenting unbalanced food webs both for benthic and fish communities. Therefore, the present results support a high trophic resiliency of fish communities, likely as a result of functional redundancy of fish predator species. In summary, through innovative and large-scale ecological surveys this thesis contributed to assessing Mediterranean MPAs efficacy, to address possible management solutions to reduce pre-existing conflicts between MPA stakeholders and fishers, and to understand the direct and indirect ecosystem-level impacts of OA scenarios on benthic and fish assemblages.

CO2 concentration in the atmosphere is increasing at unprecedented rate since the last 800,000 years due to rising fossil fuel combustion, industrial processes and land use by humans. By absorbing part of this gas from the atmosphere, Oceans contribute to the mitigation of climatic changes, but at the cost of greater modifications of their physical and chemical characteristics. CO2 dissolved in the seawater leads to increased bicarbonate (HCO3 -) and hydrogen ions (H+) concentrations with a consequent pH drop, a phenomenon known as Ocean Acidification (OA). If global policy will not put in force mitigation measures to reduce CO2 emissions, it is projected that partial pressure of dissolved CO2 (pCO2) will increase up to 600-700 μatm by 2050 and up to ~1000 μatm by 2100. At the same time, ocean surface pH is predicted to further drop by 0.3- 0.4 units by the end of this century. OA is considered one of the most serious threat for marine organisms and ecosystems, and this topic was the most studied field of investigation between 2000 and 2013. Several quantitative reviews based on meta-analytic approaches allowed some generalizations on the sensitivity of marine species to elevated pCO2 levels and lowered pH showing that OA expected for next decades would negatively affect survival, calcification, growth and development of a wide variety of taxa. Calcifying organisms are considered the most threatened group, as increase of hydrogen ions concentration may also determine the decrease of saturation states with respect to aragonite and calcite, two forms of calcium carbonate forms commonly used for building up organisms’ shells and skeletons. However, expected CO2 levels in the ocean may also affect several biological processes of non-calcifying organisms. In the last decade, a growing number of studies focused on the impact of elevated CO2 concentration on fish. The vast majority of these studies was conducted under controlled laboratory conditions and showed highly variable sensitivities among species, making difficult to reach some generalization on the possible future impact of this environmental change. The general aim of this thesis was to assess how elevated CO2 may affect different biological processes of marine teleost fish through field-based and laboratory experiments. For this purpose, I investigated the response of tropical and temperate species during different life stages (from embryos to adults) and at different organization level (from individuals to community). The first aim of my thesis was to depict the state of the art on ocean acidification effects on fish worldwide. This goal was achieved through a quantitative review of papers published until June 2016 (chapter 2). Specifically, through a mixed-effects meta-analytic approach, I provide the first comprehensive global analysis of eco-physiological, developmental, and behavioural responses of fish to expected CO2 levels in the near-future ocean. To assess if such responses may be mediated by fish characteristics, I evaluated the role of different life history traits (e.g. climatic zone, life stage, physiology, and habitat) in modifying fish sensitivity to OA. Results showed that, if anthropogenic CO2 emissions continue to rise, significant effects of elevated CO2 levels on fish mortality, calcification, and behavioural performances are expected to occur in the next decades, particularly for larvae. Some effects may be more subtle than expected, as mortality rates per se may be enhanced by observed decreasing growth of larvae and higher predation riskunder elevated CO2. Despite some specific fish traits might mediate the responses of fish to OA (e.g. I found differences in behavioural impairments levels between tropical and temperate species), my analyses failed to find a single life history characteristic potentially confering fish tolerance to elevated CO2. A strong need to expand the number of OA studies to multi-generational, multi-stressor and species interactions experiments is also discussed. The following three chapters dealt with the effects of OA on embryos, juveniles and adults of a temperate wrasse species (Symphodus ocellatus) living off a volcanic CO2 seep site (Vulcano island, Italy). It has been widely demonstrated that fish reared at elevated CO2 concentrations display severe behavioural disruptions, such as altered lateralization, increased activity rates, unability to recognize olfactory cues. These effects have been mainly investigated in laboratory conditions and only two studies evaluated the impact of OA on behaviour of fish chronically exposed to elevated CO2 in the wild. Moreover, no previous studies focused on the possible effects of OA on fish reproductive behaviour. Chapter 3 provided the first evidence of the effects of ocean acidification on reproduction of fish in the wild. Specifically, I assessed how different CO2 concentrations may alter key mating behaviours and spawning ability in a species with different typologies of breeding males (dominant nesting, satellite and sneaker S. ocellatus males). Results showed that dominant male mating behaviour was unaffected, as courtship and nest defence did not differ between sites under ambient and elevated CO2 concentrations. However, dominant males experienced significantly lower rates of pair spawning at elevated CO2 levels, despite maintaining a trend of higher paternity than sneaker and satellite males. The chapter 4 assessed the influence of increasing CO2 concentrations on the metabolic rate (oxygen consumption) and the development of ocellated wrasse early life stages. For this purpose, I ran translocational experiments in the field, by collecting embryos from nesting sites with different pCO2 levels and transplanting embryos from ambient- to high-CO2 sites for 30 h. Results showed that ocellated wrasse offspring brooded in different CO2 conditions had similar metabolic responses, but embryos from parents that spawned in ambient conditions had higher metabolic rates and a smaller size at hatching when transplanted in the high-CO2 site. However, the adverse effects of increased CO2 on metabolism and development did not occur when embryos from the high-CO2 nesting site were exposed to ambient conditions, suggesting potential parental effects as offspring from the high-CO2 nesting site could be resilient to a wider range of pCO2 values than those belonging to the site with present-day pCO2 levels. The chapter 5 focused on the ability of S. ocellatus recruits to recognize their predator under elevated CO2. Several studies showed that fish exposed to CO2 concentrations expected for the next decades are potentially more sensitive to predation, as they show bolder behaviour and appear to be attracted from cues they normally avoid. However, treatment with gabazine - a neuroreceptor GABA antagonist – restore the normal behaviour. These evidences have been described mostly through short-term laboratory trials on tropical fish species, whilst experiments on temperate fish from populations chronically exposed to elevated CO2 in the field have been seldom carried out. I investigated whether recruits (i.e. settled larvae) of the ocellated wrasse S. ocellatus from high CO2 recruitment sites off a volcanic seep lost their ability to recognize the odour of a common predator. Results showed that fish, treated or untreated with gabazine, both from ambient and high CO2 sites, displayed a similar avoidance of predator odour, suggesting that ocellated wrasse recruits could be tolerant to rising CO2. This study adds on previous evidence that temperate fish species might exhibit higher resilience to OA than tropical species. The chapter 6 evaluated how short-term exposure to high CO2 concentrations may influence the escape response and the shelter use under predation risk of juveniles of the tropical damselfish Chromis viridis. For this purpose, I ran two different experiments in aquaria, by measuring the escape response kinematic and the use of shelter of groups of damselfishes reared for 5 days under different CO2 conditions (ambient and high CO2 concentrations) in presence/absence of their predator, the black tip grouper Epinephelus fasciatus. Whereas high CO2 had no effect on the escape performance of C. viridis, their use of shelter was significantly impaired, as juveniles reared at acidified conditions spent more time outside and ventured farther from the refuge than those reared at control conditions. The chapter 7 documented how OA may indirectly affect the composition and structure of fish communities via biogenic habitat shifts in CO2 seeps off Japan. Many recent studies suggested that elevated CO2 may affect the structural complexity of biogenic habitats, altering the species composition of the associated fauna and amplifying the indirect negative effects of OA on the biodiversity they support. By now, only two studies empirically estimated the indirect effects (via biogenic habitat change) of ocean acidification on fish assemblages, showing contrasting results. Long-term elevated CO2 did not lead to changes in reef fish community composition and structure in Papua New Guinea, whereas community effects were recorded on temperate coastal fish assemblages in CO2 seeps off Italy and New Zealand. Here, I coupled fish and benthic community surveys (complexity, canopy, % cover of main biogenic habitats) at and around natural CO2 seeps off Shikine Island (NW Pacific, Japan) to assess how OA-mediated changes of biogenic habitat may alter structure and composition of reef fish communities. Results showed shift in biogenic habitats from zooxanthellate scleractinian corals and high profile macroalgae in ambient CO2 sites to small turf algae in elevated CO2 sites, and rather consistent changes in the associated fish communities with a clear diversity loss.

Over the past few decades we have witnessed rapid ecological changes that have occurred in the world's oceans and that have mainly affected the resilience and resistance of ecosystems and the vulnerability of communities living in these ecosystems. The real challenge will be to identify and select techniques and approaches based on a macroscopic vision in order to reduce the effect of global warming, the impact of human activities and their consequences on the marine environment. These interactions can generate effects that influence the functioning of oceanic and coastal ecosystems and, consequently, goods and services, such as fishing and aquaculture production. In fact, these activities must be managed and administered responsibly to avoid competition for space which cause numerous conflicts and increase the human impact on ecosystems. In Europe, the Marine Strategy Framework Directive (MSFD) was established in 2008. It represents an important legal instrument for Member States to protect and preserve the marine environment, prevent deterioration and, where possible, restore marine ecosystems in areas where they have been damaged. The directive obliges Member States to determine the characteristics of "Good Enviromental Status" (GES) defined by descriptors, criteria and indicators. This assessment should be carried out in a complementary manner by all Member States, however, in most countries the precise means of implementation of the MSFD are not yet clear. To meet the necessity to increase MSFD implementation, we need to gather organic information in order to better address the decision making process. Here, the chapter 1 proposes an "analysis of the evidence", by which I defined a complete picture of the EU Marine Strategy showing important gaps of the type of approaches and the means to be used for a correct analysis of the state of the environment. Based on this analysis, I selected two MSFD descriptors (D. 2 ―Non-indigenous species‖ and D. 3 ‖Commercial species‖) which were the main subject of the following chapters. Chapter 2 aims to study the effect that climate change, specifically the increase of temperature, had on the presence of non-indigenous species (NIS) in the entire Mediterranean basin. In this basin, complex and fundamental alterations which have consequences on the structure and functioning of the sea and the consequent supply of goods and services, are still underway. Furthermore, threats due to temperature increase may also alter the spread of shellfish aquaculture, hitherto recognized as the best candidate for mitigating the effects of overfishing. This topic was developed in chapter 3. In fact, by using a study carried out along the Italian peninsula, we highlighted the effects of the increase in temperature on the model species, Mytilus galloprovincialis. This was done by measuring the characteristics of the thickness and the condition index. This information will be invaluable for the examination of any possible deviation from natural models due to the increase in temperature and could represent an important context in which to face the future understanding of the feasibility and reliability of the economic activities of shellfish aquaculture. Lastly, in chapter 4, the main objective was to understand and predict the possible impacts of one among the most important human economic activities: aquaculture in coastal habitats. The main question was about the possibility of combining the experimental procedures with the mechanistic bioenergetic models based on functional traits, in order to effectively predict the life history traits of the cultivated species. The need to adopt an ecosystem approach to site selection and the need to define the allocation of areas dedicated to aquaculture activities in the wider context of marine spatial planning, requires the use of modeling tools to support decision-making in aquaculture. Therefore, the main objective of my thesis was that to determine cumulative pressures caused both by the increase in temperature and by human activities, so as to provide useful information for the destination and sustainability of use of Marine Spatial Planning (MSP), in the evaluation of the GES, using an ecosystem-like approach.

Despite the field of invasion ecology has rapidly grown, the mechanisms behind the invasion success of alien species and the biotic resistance to invasions still need a thorough understanding. Comprehending the response of resident assemblages to biological invasions and the possible impacts produced by alien species introduction is, therefore, crucial to expand the current knowledge of the invasion process in the recipient systems. In this thesis different aspects of biological invasion process have been critically examined emphasizing the importance and complexity of the interactions between alien species and native biota, in the Mediterranean marine coastal ecosystems. Here, five different invaders were used as model organisms: two seaweed species, Caulerpa cylindracea and Caulerpa taxifolia var. distichophylla, the crab Percnon gibbesi and two rabbitfish species, Siganus rivulatus and Siganus luridus. Firstly, in Chapter 1 a general overview of the invasion processes was provided. The following two chapters were focused on the interactions between the generalist native herbivore, Paracentrotus lividus, and the two co-occurring alien seaweeds C. cylindracea and C. taxifolia var. distichophylla. Specifically, in Chapter 2 the feeding behaviour of P. lividus was investigated in order to predict the potential vulnerability of the two alien seaweeds (alone and intermingled) to sea urchin grazing and the possible biological control exerted by the native herbivore on the two seaweed populations. The results from feeding choice experiments showed that P. lividus is able to incorporate in its diet the two co-occuring alien seaweeds suggesting a potential capacity of the sea urchin to control their expansion in the invaded area. Chapter 3 aimed to investigate the potential physiological stress induced on P. lividus by the consumption of the two alien seaweeds, C. cylindracea and C. taxifolia var. distichophylla. Based on the presence of chemically distinct toxic metabolites in the two invaders, a synergistic effect of toxic metabolites on the sea urchin righting behaviour was predicted, when the two algae were consumed simultaneously. The findings showed a significant increase of P. lividus righting time as a consequence of the simultaneous consumption of the two alien seaweeds, suggesting that synergistic interactions among the two invaders can enhance their likelihood to survive. Reduction in sea urchin performance may have negative implications for their overall grazing activity and, ultimately, for their ability to control the expansion of alien seaweeds in the invaded area. More generally, it is well-known that native-alien species interactions may influence the invasion process favoring or hindering the establishment and spread of alien species. As predicted by theory, the success of alien species can be restricted by interspecific interactions, such as competition and predation, from resident species. Therefore, pristine communities, with high species richness and diversity, are less prone to invasions than those already degraded by human activities. In this regard, Marine Protected Areas (MPAs), supporting a greater number of species than unprotected areas, are expected to limit the successful establishment of undesirable invaders. In Chapter 4 it was tested if the high native diversity observed within MPAs can provide biotic resistance to the invasion of the alien crab P. gibbesi compared to fished areas. Results revealed a negative relationship between the diversity of native communities and the invasiveness of the alien crab. Specifically, it was shown that MPAs, as protected systems with high native species richness and diversity, may hinder the spread of the high invasive crab P. gibbesi. Finally, evidence from the Mediterranean Sea showed that the invasion of herbivorous fishes may induce phase shifts in the recipient communities. In the last chapter (Chapter 5) the relationship between the biomass of two alien herbivorous fishes (S. luridus and S. rivulatus) and the cover of barren was investigated in sublittoral rocky reefs across the Aegean Sea. Results showed that the biomass of the two alien fishes was positively correlated to the barren cover reinforcing the idea that these invaders are able to induce shifts from diverse and productive algal forest to the low-complex barren state, affecting the structure and composition of the shallow rocky reefs in the Mediterranean Sea. All findings of this thesis have interesting implications for the potential mechanisms of invasion process and contribute to the increase of knowledge on the invasion dynamics, reinforcing the idea that biotic interactions are among the main drivers affecting alien species invasion process.

The southern Sicilian coast represents an important contribution to Italian tourism, the Sicily Channel is an important communication path because at the top of its seafloor there are many pipelines, and submarine communication cables which are laid to carry signals, and which are very important to the minor islands. In this work, we are presenting results of the detailed geomorphological and seismostratigraphic analysis based on new very high-resolution dataset (multibeam and CHIRP) acquired during the ACUSCAL 2015 Cruise. We also used low resolution bathymetric and seismic data provided from online database (ViDEPI, GEBCO, EMODnet). This study allows us to reconstruct the tectonic volcanic mass movement and bottom current processes and to identify and map several relative geological elements (e.g. fluid escape structures, gravity driven deposits, volcanic morphologies) which were used to describe the geological setting of the study area. The latter is a small area (approx 100 km2) located in a shallow sector of the north-western Sicily Channel, at a distance of 45 km from the Sicilian coastline, where seven seamounts (M1-M7) have been identified and studied between 10 and 350 m in depth. In the study area, the interaction of the sedimentary multilayer (e.g. Holocene sedimentary body, Messinian Evaporites) and the volcanic context (i.e. Graham Bank) with the tectonic activity (shallow and deep) creates a complex and highly geological framework hosting seafloor seepage. The main focus is the description of the fluid escape structures suggesting a possible model for the origin of the fluid and the mechanisms by which it is transferred to the seafloor. Another important aim is the reconstruction of the relationship between the deep tectonic structures and the fluid escape structures in the north-west Sicily Channel. Seafloor seepage is a widespread phenomenon in the global ocean forming important seafloor morphologies. It affects the global carbon cycle and provides the basis for abundant chemosynthetic organisms living in and on the seafloor. In this Ph.D. project, detailed investigation about the geological setting of such sites and the controlling factors for spatial and temporal distribution of the fluid escape structures were indispensable to understand the “fluid flow system functions” This work is a prime example of these interactions and their influence on seafloor seepage in the Western part of the Sicily Channel. Many pockmarks, mounds and some active seafloor seepages (i.e. hydro acoustic anomalies) have been identified and investigated using both stratigraphic information provided by AGIP/ENI Wells in conjunction with various geophysical data primarily multibeam and Chirp and secondarily multichannel seismic profiles and low resolution bathymetric data. The accurate bathymetric surveying by multibeam instruments allowed us to recognise several positive (mounds) and negative morphologies (pockmarks) linked at the fluid escape phenomena. The bathymetric data revealed an increase in size of the pockmarks with increasing distance to the elongated channel located in the central part of the study area and also that both pockmarks and mounds are isolated, aligned or clustered. CHIRP profiles imaged the presence of several recent faults affecting the Holocene sedimentary body and the occurrence of hydro-acoustic anomalies in the water column, located mainly at the top of the recognised volcanoes. The Multichannel seismic profiles that were correlated with the Agip/Eni wells, showed several acoustic anomalies (often from the Messinian Evaporites) and sub vertical normal fault systems, which affect gas migration in the sub-seafloor. In the western part of the study area, the Messinian Evaporites rise up to the seafloor with a jagged seafloor topography of the MES deforming the complete geological succession. Additionally, the volcanic context supplies large volumes of material to the seafloor, which are distributed as seamounts. The uplift of Messinian deposits concurrently with the formation of sub vertical normal faults leads to gases/fluids migration towards the seafloor forming a field at pockmarks of different sizes. In the eastern part, the rise up of volcanic material through the sub vertical normal faults leads to gases/fluids migration towards the top of the seamounts forming vertical plumes. The first study case of this work revealed a strong tectonic control on the development and distribution of the seepage features in the study area. The aim of the second study case of this work was the identification, description and classification of different examples of gravity driven deposits. The recognised gravity driven deposits in the study area using CHIRP and Multibeam data are: (i) soft-sediment depositional structures (SSDSs), (ii) rock falls and (iii) large debris avalanches. We however estimated the main pre-conditioning geomorphological factor, which could have induced sediment instability and the trigger mechanisms often linked to different geological processes. This second study case revealed that these geomorphological structures are characterised by a genesis probably linked to elevate slopes of the seabed as well as trigger different factors. Finally, mainly using the multibeam data and secondarily the CHIRP data, a cluster of seamounts that was recognised within the study area have been investigated and studied in detail. Their main dimensions and relative physical parameters have been measured and tabulated, allowing a morphometric and morphologic classification on the basis of their shapes. Several restrictive criteria were applied in order to be ceratin of their volcanic origin (conical shape with maximum height, basal ratio, aspect ratio) obtaining finally what can be classified as volcanic seamounts. These structures are very similar to submarine volcanoes described elsewhere on the seafloor. Some show at the top plain morphologies interpreted as marine terraces, others show a typical cone shape of the volcanoes one of which is characterised by a complex shape. On the basis of their morphological features these have been subdivided into three categories.

Major volatiles play an important role in subduction zone magmatism, from magma generation in the mantle, to crustal ascent and evolution, until its dramatic expression during a volcanic eruption. In the attempt to add a piece of information on source and behavior of major volatiles in arc volcanism, I here report on the geochemistry of H2O, CO2, S and Cl in two volcanic systems in NW Nicaragua (Central America), San Cristóbal and Telica. The observational approach is based upon combination of some of the most recent techniques in volcanic gas monitoring and petrology. I here explore quiescent and eruptive degassing processes by combining both volcanic gas and melt inclusion approaches. Field gas measurements were primarily obtained via the Multi-Component Gas Analyzer system (Multi- GAS) technique, complemented with additional remote sensing observations via open-path Fourier Transform IR (OP-FTIR) spectroscopy, ultraviolet differential optical absorption spectroscopy (UV-DOAS). These techniques together allowed characterizing compositions and fluxes of CO2, H2O, S and Cl in the central crater plumes of both quiescent degassing volcanoes. These measurements contribute to our understanding of the current structure and state of the shallow plumbing systems that feed the surface gas emissions. The targeted San Cristóbal and Telica volcanoes are also investigated by characterizing, for the first time, the volatiles contents (CO2, H2O, S and Cl, F) in their melt inclusions. Using a series of laboratory instrumental facilities, such as electron microprobe, micro FTIR spectroscopy, Raman spectroscopy and Nano secondary ions mass spectroscopy (NanoSIMS), I show that olivine- and pyroxene-hosted melt inclusions can reveal crucial information on preeruptive magma conditions at both San Cristóbal and Telica. I propose that polybaric degassing and crystallization models can suitably describe major volatile abundance and behavior during magmatic evolution. These results are synthesized in 3D illustrative sketches that represent the crustal structure of San Cristóbal and Telica volcano-magmatic systems. Water is the primary agent during magmatic fragmentation and strongly influences eruptive style. CO2, the second most abundant volatile in magmas, is generally more difficult to quantify in melt inclusion studies, but its role in volcanic processes is revealing more and more important as volcanological research advances. I therefore spend major attention in this study to charactering the carbon content in San Cristóbal and Telica primitive magmas. CO2, apart from being an excellent chemical tracer of magmatic degassing processes, is one of the most important triggers of explosive eruptions in basic to intermediate magmas. The volatile contents of Central American magmas show wide regional-scale variations. It is shown here that gas signature (carbon abundance) of Central American volcanic gases correlates with petrological tracers of magma compositions, and specifically with the trace element proxies of slab-fluid contribution to the mantle wedge. This brings novel constraints on carbon source in volcanic arc regions. I also show, using noble gas isotope compositions of fluid inclusions in olivine-pyroxene crystals, that a common mantle fluid signature persists along the entire Nicaragua volcanic segment. Controls on magma generation are, instead, better reconstructed using incompatible trace elements; these data reveal that the degree of mantle melting and sedimentary fluid incorporation are higher in Nicaragua than in other sectors of the arc. We find that local variations exist also at the scale of a single magma system. These variations, at different spatial and temporal timescales, prove that regional compositional heterogeneities exist underneath volcanic arcs.

This thesis deals with the patterns of tectonic deformation at different time and spatial scales ranging from tens to millions of years and from one to tens of kilometers, respectively. The study areas are the Campi Flegrei (Campania region, Italy) and Paola Basin (western offshore Calabria region, Italy). The Campi Flegrei and its offshore prolongation, the Pozzuoli Bay, are a laboratory for investigating volcano-tectonic deformations at 1yr-1kyr timescale and 1km spatial scale related to the dynamics of the Neapolitan Yellow Tuff (NYT) caldera and its intra-caldera resurgence. Resurgence is the late stage, long-term uplift of a collapse caldera floor to form a dome-like structure. The comprehension of its development and structural pattern is crucial for predicting the caldera behaviour during periods of unrest. This work investigates the resurgent activity of the NYT caldera using an integrated analysis of high-resolution swath bathymetry, reflection seismic profiles and interferometric synthetic-aperture radar (InSAR) data. The interpretation of the data shows that resurgence affects a ~ 50 km2 wide almost circular area centred in the Pozzuoli harbor. The resurgent area is surrounded by a ~ 3-4 km wide structural discontinuity corresponding to the Ring Fault Zone (RFZ) that formed during the NYT caldera collapse (~15 ka BP). The uplift of the caldera resurgence occurs along a series of inward-dipping reverse faults of the RFZ characterized by a decreasing-upward inclination of fault planes from ~70° to ~15°. The development of these structures is controlled by the reactivation and deformation of pre-exiting normal faults associated with the NYT caldera collapse. Deformation of reactivated faults often results in folding of overlying and/or juxtaposed strata, in the style of ~ 500 m wide antiformal folds, mostly located along the periphery of the resurgent area. The structural pattern of the resurgence consists of disjoint uplifted blocks of the caldera floor. Two main structural elements are detected inside the resurgent area both off- and onshore, separated by a NNE-SSW trending high-angle normal fault. The most uplifted block comprises the area from Mt Nuovo to La Pietra, whereas the adjacent uplifted sector extends eastwards to include Mt Spina. The morpho-bathymetric expression of the two uplifted blocks is represented by a ~5 km wide antiformal structure, encircled by Bagnoli and Epitaffio valleys. In the hinge zone of the resurgent dome a series of high-angle normal faults form a small apical graben. In order to analyze long term deformations (Myr timescale) occurring at a tens of kilometers spatial scale, this study focuses on the Paola Basin, a segment of the forearc region of the Tyrrhenian-Ionian subduction system. Fore-arc basins are parts of fore-arc region that form structurally in response to a variety of subduction zone processes. The sedimentary infill records the complex tectono-stratigraphic evolution of basin associated with subduction system, and thus, allows deciphering the formation mechanisms of basins developed in compressional intraplate settings. We analyse these processes in the Paola Basin using reflection seismic profiles and bathymetric data. The Paola Basin is a NNW-SSE trending asymmetric syncline, bounded by the offshore sector of the Coastal Chain to the East and by the regional-scale Paola Anticline to the West. It hosts up to 5.5 km thick Plio-Quaternary deposits, most of them showing eastward-dipping clinoforms. These latter are associated to shelfal progradation, supplied from the north via longshore currents, dispersing sediments from unknown Apenninic/Sila entry points. A local circulation of longshore currents flowed southwards and dispersed sediments from unknown Apenninic/Sila entry points. An aggradational internal geometry characterizes the uppermost part of the sedimentary infill with a thickness decreasing westwards, suggesting a sediment supply from the Coastal Chain. In the Early Pliocene, the proto Paola Basin extended from the Paola Anticline up to the western flank of the Sila Massif. Since ∼ 3.5 Ma, the uplift of the Coastal Chain shortened the proto Paola Basin, leading to the separation of the basin from the Crati basin. Short wavelength (∼ 80 km) lithospheric buckling, caused by a ENE-WSW oriented, arc-normal paleo-stress field, is the most likely mechanism that explains the pattern of tectonic subsidence of the Paola Basin, the uplift of the Paola Anticline and part of the uplift experienced by Sila Massif during the Plio-Quaternary. Kilometre-scale, strike-slip restraining and releasing bends are widely spread over the hinge zone of the Paola Anticline, defining the Paola Ridge. Their formation is compatible with an NW-SE oriented maximum stress axis meanwhile strike-slip fault accommodates the arc-parallel component of the plate motion. The change in direction from ENE-WSW to NW-SE of the maximum stress axis in the fore-arc region is a consequence of the transition from orthogonal to oblique subduction, associated to the bending of the Northern Calabria Arc. Regional uplift and folding of the Northern Calabrian Arc induced tensile stress resulting in the formation of N-S trending normal faults in the extrados of the Sila Massif anticline. In this context, the Paola Basin can be defined as a “Neutral Accretionary-type” forearc basin.

Lipids provide the expendable form of energy in marine ecosystem, and have an important role for the reproductive biology of fish. Also, lipids are important nutrients, versatile markers for marine trophic studies, bacteria markers etc. Among the lipids, several essential fatty acids are determinants for ecosystem health as well as for their known nutritional properties and prevention capacity of chronic diseases. Furan fatty acids (F - acids) are other important lipid bioactive compounds; for these is hypothesized a crucial nutritional role that is synergistic to polyunsaturated fatty acids omega 3 (PUFA ω 3), also if their mechanism is not yet clear. Source of essential fatty acid is the anchovy (Engraulis encrasicolus, Linneus 1758), which is the most important commercial coastal pelagic species of the Mediterranean Sea and highly recommended for human nutrition. Although in literature there are numerous studies on the lipid composition of the anchovy during seasonal changes, studies regarding the species caught in the Sicilian Channel (GSA 16), south Sicily (Italy) which represents an important reference point for the fishing of pelagic fish in all the Mediterranean, have not been carried out. This Ph.D. thesis presents and discusses the variables contributing to lipid composition of Engraulis encrasicolus of the Sicilian Channel, Central Mediterranean Sea (Italy); in particular investigates the tissues (edible muscle, gonads and liver) and fatty acids distribution during catching season (between December 2014 to November 2015) and correlates the data to environmental parameters obtained by satellite as Chlorophill-a and Temperature (≤ 100 m from surface). The specimens were analyzed for sex and size classes, and the analysis of fatty acids, furan fatty acids, cholesterol were performed by GC/MS while total lipids by gravimetric method. One of the first results concerns reproductive status. The anchovy season spawning ranged from April to September, also if was observed an advance of the peak reproductive than literature, probably due to increase of surface temperature sea in the last three years (about 3 %). The results showed that the period of the biggest accumulation of lipids, both for edible part than organs, is winter, with values higher (p < 0.05) for females than males (22.78 ± 0.86 % vs 16.48 ± 0.42 % in March) and for different size classes (age). For example the highest percentage for females of 130 - 139 mm size class was 22.78 ± 0.86 % which have mainly one year old and not yet subject to reproduction, vs 17.78 ± 0.42 % for individuals of 150-159 mm (mainly 2 year ald). An positive correlation between total lipid and cholesterol was observed. Unlike the lipid amount, the PCA showed that the fatty acid composition of anchovy depends mainly of the physiological states of animals regarding their reproductive status and no from also sex and size class. In fact, all fillets of anchovy and liver organ reported higher values (p < 0.05) of PUFA ω 3 and lower values of saturated fatty acids (SFA) during reproductive cycle than autumn - winter. For example, in edible muscle the highest percentage of PUFA ω 3 was observed in April 42.17 ± 0.46 % and the lowest in December 34.56 ± 0.30 % (p < 0.05), while % SFA from April to September was about 35 % vs December - March about 40 % (p < 0.05). At the same time, a decreasing trend was observed, specially for docosahexaenoic acid DHA in sexual organs. DHA dropped (p < 0.05) from April (29.33 ± 0.10 %) to September (23.83 ± 0.47 %). High concentration of PUFA ω 3 and PUFA ω 6, and the seasonal variation of F - acid both muscle than organs are the important fingerprints of anchovy of Sicilian Channel than literature. This thesis, in fact, is the first study that quantify the F - acids amount in Engraulis encrasicolus of Sicilian Channel and shows that higher percentage of F - acids is measured mainly during spring - summer (however small quantity < 1%) and traces in autumn - winter (< 0.001 %). In addition the high concentration of PUFA ω:6 has been compared with Chlorophill-a concentration, and its increase of about 20 % in the last three year respect to 1998 - 2002, could be cause of changes of diet of animal, supported also of decrease of specific monounsaturated fatty acids (MUFA) markers of animal food fraction than literature. This thesis represent an important study on physiological state of anchovy Engraulis encrasicolus (Linnaes 1758) of Sicilian Channel through lipid markers in relation to environmental variables. Another theme concerns the fish safety, in fact due to the high perish ability of the fish, new technologies and fast and low-cost methods are necessary to control the hygienic conditions during all seafood chain, and the analysis of fatty acids could help. The analysis were performed by GC/MS on samples fish preserved a 7.4 ± 0.1 °C for total two weeks (gut and muscle) and bacterial colture. This study shows that fatty acids with odd number of carbon atoms as C13:0, C15:0 and only one fatty acid with even number of carbon atoms as C12:0 displayed an increase during storage period. An increase of about 70 % al 7th day and 90 % at 14th in edible muscle was observed, while omega 3 decreased of about 50 % and 80 % in muscle and gut, respectively. The presence of these fatty acids in bacterial colture and mainly in literature, suggests them as bacteria markers, and so the fatty acids analysis could be applied to assess and distinguish the freshness as well as the improper storage of the fish product. This method appropriately improved, can be also used in situ and to be another means to investigate the fish safety.

Volcanic gas emissions carry crucial information on pre- and syn-eruptive processes, and on behaviour of active volcanic systems. Gas variations arise from replenishment of magma storage zones with mafic magma, from magma ascent and evolution, and from interaction with hydrothermal systems and volcanic lakes. As such, volcanic gases represent “open windows” into genesis and release of volatiles from the Earth’s interior. Volcanic emission measurements allow understanding subsurface magmatic and hydrothermal processes, and contribute to eruption forecasting. Carbon dioxide and sulfur gas represent the most abundant and studied gas species. In particular, CO2, due his fast exsolution during magma decompression, represents an important parameter for volcanic hazard assessment. In addition, due to his greenhouse effect, quantification of CO2 budget from natural emissions at global scale represents a key scientific challenge. Indeed, active volcanic systems are able to release considerable quantities of gas. Volcanic arcs, in particular, release large amounts of CO2 due to carbon recycling from subducted sediments and crust, and due to fluid addition from the mantle wedge. Understanding and modelling these processes allow forecasting volcanic eruptions, quantifying the volcanos’ total volatile budgets, and contributing to climate change modelling. In the past years, the scientific community has made efforts in order to discriminate the role and contribution of subducted slab sediments and altered oceanic crust on the geochemistry of magmas in volcanic arcs worldwide. New geochemical tracers and isotopes, in tandem with other volcanological data, has allowed characterizing the mantle source. In spite of the efforts made, many active volcanic systems are still poorly studied and monitored, and an improved knowledge on dynamics of volcanic degassing and in global gas budgets are needed, with particular attention to carbon dioxide. Technological progress has brought significant advances in geochemistry. Unlike the past, new instrument allow to continuously monitoring volcanic gas, reducing drastically the risks for the operators. In this study (chapter 4, 5, 6), I took advantage of the recent advent of new techniques such as the Multi-GAS (Multi-component gas analyser system) and the Ultraviolet dual camera instruments. The Multi-GAS can perform gas measurements in a fully automatic way, while UV cameras allow measuring SO2 fluxes with high spatial/temporal resolution. Combining gas chemical composition (Multi-GAS) with SO2 flux (UV dual camera), it is possible to estimate the gas fluxes of other gas species. My PhD focused on characterizing gas compositions and fluxes from three most active volcanoes in the Central America Volcanic Arc (CAVA): Pacaya (Guatemala), Masaya (Nicaragua), and Rincón de la Vieja (Costa Rica). At Pacaya (Guatemala), I used a multi-disciplinary approach, combining geochemistry of gas and rocks, in the attempt to gain insights into the magmatic gas signature, on the volatile budget, and for characterizing the mantle source. Plume compositional data suggest Pacaya exhibits a H2O-poor (for an arc volcano) composition (80.5 mol. %), with a characteristic magmatic CO2/St ratio of ~1.0 to 1.5. Both the H2O-poor and low CO2/St ratio composition concur to suggest a limited slab-fluid contribution (at least compared to other volcanoes/arc segments; Aiuppa et al., 2017), and a dominant mantle-wedge derivation of the emitted volatiles. The 3He/4He ratios measured in fluid inclusions hosted in olivines (Ra) are the highest values in CAVA volcanism. This strongly supports that the mantle source beneath Pacaya lacks of any contamination of radiogenic 4He from the slab or the crust. At Rincón de la Vieja (Costa Rica), I combined gas geochemistry with volcano seismicity in order to derive constraints on the triggers of phreatic/phreatomagmatic explosions. For the first time, the composition of the gas released during discrete phreatic events (confirmed seismically) was resolved using Multi-GAS. The results demonstrate chemically distinct gas compositions during quiescent degassing versus explosive eruptive degassing. These results confirm (Christenson and Tassi, 2015) that the complex interplay between rising magmatic gases and sublimnic hydrothermal systems likely play a decisive role as eruption triggers. On Masaya (Nicaragua), I combined ground-based gas measurements and space-based thermal data in order to evaluate changes in gas composition associated with resumption of lava lake activity in 2015, and to derive novel information on the driving magmatic processes. Our results show that appearance of the lava lake in December 2015 was anticipated in mid- to late-November by a noticeable volcanic gas plume compositional change toward more CO2-rich compositions, and by a sizeable CO2 flux increase. Moreover, in view of the paucity of helium isotopes data for the northern part of CAVA, I collected rock samples on Pacaya and in 3 volcanoes in El Salvador (Santa Ana, San Miguel and Ilopango volcanic systems) to performe noble gas isotopes measurements in fluid inclusions. The data obtained here refine previous results obtained for the CAVA arc and suggest that 3He/4He along CAVA shows a regional trend as observed for other geochemical tracers (e.g., Ba/La, C/S, see chapter 7). The general of this work is to expand gas knowledge on poorly studied volcanic systems, improve the geochemical database of Central America, and contribute to a better understanding of magmatic and geochemical processes in convergent margins.

Nel corso degli ultimi 200 anni, circa il 30% delle emissioni antropogeniche di CO2 nell’atmosfera sono state assorbite dagli oceani, provocando un abbassamento medio dei livelli di pH oceanici pari a circa 0.1 unità. Questo fenomeno, noto come acidificazione degli oceani, sta determinando conseguenze negative sugli ecosistemi marini e sul loro funzionamento. Le attuali proiezioni climatiche suggeriscono che, in futuro, i cambiamenti climatici continueranno e si intensificheranno se non verranno adottate efficaci misure di mitigazione. Riuscire a valutare la risposta degli ecosistemi marini ai cambiamenti climatici costituisce una vera sfida per la ricerca scientifica, non solo per la difficoltà di prevedere gli effetti congiunti di cambiamenti che agiscono simultaneamente su scale differenti (globale e regionale), ma anche per la necessità di indagare gli effetti delle interazioni interspecifiche tra organismi viventi nel contesto delle modificazioni ambientali in corso. Lo scopo di questa tesi è stato quello di valutare gli effetti dell’acidificazione oceanica su comunità marine costiere, con particolare riguardo alle praterie di Posidonia oceanica e alle comunità di biofilms microbici. Considerato il recente riconoscimento dei sistemi idrotermali marini superficiali (CO2 shallow-water vents) quali analoghi di futuri oceani acidificati, sono stati condotti tre studi presso i vents di Panarea e Vulcano (Isole Eolie). Nel primo studio, sono stati indagati gli effetti a lungo termine dell’acidificazione sulle praterie formate dalla fanerogama P. oceanica. I risultati delle ricerche condotte presso l’isola di Panarea, hanno dimostrato che il posidonieto è particolarmente sensibile all’incremento di CO2 e alla riduzione di pH causato dalle emissioni di vents superficiali: le praterie vicino ai vents sono risultate meno dense e caratterizzate da fasci più corti e soggetti ad un turnover fogliare più rapido. E’ stato inoltre osservato che le foglie, generalmente di dimensioni ridotte rispetto a quelle di praterie non esposte alle emissioni idrotermali, avevano un minor numero di apici rotti, presumibilmente a causa dello scarso ricoprimento di epifiti rinvenuto sulle stesse, nei siti acidificati. In futuro, una ridotta canopy e una minore appetibilità di P. oceanica conseguentemente all’acidificazione delle acque, potrebbero determinare una compromissione del ruolo chiave ecologico svolto da questa fanerogama negli ecosistemi costieri del Mar Mediterraneo. Il secondo studio ha analizzato gli effetti dell’acidificazione oceanica su comunità di biofilms microbici marini. La composizione tassonomica della comunità è stata valutata mediante un esperimento di colonizzazione lungo gradiente di pH nella Baia di Levante (Vulcano, Isole Eolie), sito già noto nell’ambito delle ricerche di settore. La composizione della comunità è risultata caratterizzata da abbondanze di taxa batterici diverse tra i siti sperimentali, con alcuni gruppi in grado di trarre vantaggio competitivo in condizioni di basso pH. Tra questi, i Gammaproteobacteria potrebbero qualificarsi come winners nel contesto dei cambiamenti climatici. Nell’ultimo studio, realizzato anch’esso presso la Baia di Levante, è stato condotto un esperimento in cui la pressione predatoria su biofilms veniva manipolata, nel contesto ambientale di acque acidificate. Lo scopo era quello di valutare simultaneamente gli effetti di processi top-down (grazing) e bottom-up (acidificazione) sulla composizione biochimica dei biofilms microbici marini. Sebbene i patterns delle diverse variabili esaminate non siano risultati sempre lineari, a causa di una elevata variabilità naturale tipica degli ecosistemi costieri caratterizzati da vents superficiali, l’acidificazione indotta dalle emissioni ha causato un aumento nelle abbondanze dei produttori primari e/o nei loro tassi di produzione all’interno dei biofilms, ed un incremento nel profilo qualitativo-nutrizionale di questa risorsa trofica. Nonostante il controllo top-down avesse condizionato la composizione biochimica del biofilms, esso non è stato in grado di contenere l’ effetto risorsa delle elevate concentrazioni di CO2 sui produttori primari dei biofilms. Alla luce dei risultati ottenuti dalle tre indagini condotte nell’ambito di questa tesi, appare chiaro che la risposta delle comunità marine all’acidificazione oceanica è altamente variabile, dipendendo non solo dai mutamenti ambientali ma anche dalle interazioni tra fattori biotici e abiotici. Over the last 200 years, about 30% of the anthropogenic CO2 emissions in the atmosphere have been absorbed by the oceans, causing a decrease in the seawater pH of 0.1 unit that is impacting marine ecosystems and their functioning. Current climate predictions suggest that, unless mitigation measures will be pursued, these changes will continue and intensify. Evaluating the response of marine ecosystems to climate change is challenging, since research efforts should not only integrate the effects of global changes with regional disturbances, but also investigate the influence of biotic interactions occurring in multiple species assemblages at the same time. The aim of this PhD thesis is to evaluate the effects of ocean acidification on marine communities in coastal ecosystems, with a special focus on Posidonia oceanica meadows as well as on marine biofilms community. Based on the recent acknowledgement of shallow-water hydrothermal vents as analogues of future acidified oceans, three studies were conducted in the Panarea and Vulcano shallow vent systems (Aoelian Islands, Italy). The first study focused on the effects of long-term acidification on Posidonia oceanica meadows at Panarea vents. The results obtained revealed that P. oceanica meadows were highly sensitive to low pH caused by the vent emissions: at these sites, meadows were less dense and characterized by shorter shoots that experienced faster leaf turnover and less grazing pressure as a consequences of the lower epiphyte biomass on the seagrass leaves. These evidences suggest that the key ecological role played by P. oceanica as foundation species in coastal environments could be compromised in the future acidified oceans. The second study focused on the composition of marine biofilms in the context of ocean acidification. The composition of the biofilm community was investigated across time at different pCO2/pH levels at Vulcano vents. Although the response was taxa-specific, significant shifts in the overall community were observed, with some groups such as Gammaproteobacteria resulting as potential “winners” in the future high-CO2 world. In the third study, a manipulative experiment modifying predatory pressure was conducted along a pCO2/pH gradient at Vulcano vents in order to determine the possible interaction of top-down (predation) and bottom-up (ocean acidification) forces on the biochemical composition of marine biofilms. Although the patterns of different variables were not always clear due to the elevated natural variability detected in the sites, ocean acidification affected the biochemical composition of the biofilms by increasing the abundance of primary producers and enhancing the nutritional quality of the biofilms. Although top-down control was important in regulating the biofilm composition, it failed at buffering the resource effect of elevated CO2 concentrations on primary producers within the biofilms. Taken together, the outcomes of these studies showed that the response of marine communities to ocean acidification is highly variable, depending not only on the environmental conditions but also on the interaction of biotic and abiotic forces.