Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme

Options:
  Reset


1 - 2 / 2
First pagePrevious page1Next pageLast page
1.
ECOLOGICAL STUDIES OF EPIKARST COMMUNITIES IN ALPINE AND PRE-ALPINE CAVES
Federica Papi, 2016, doctoral dissertation

Abstract: The karst ecosystem shows heterogeneity and variability of geology, hydrology, morphology and ecology in space and time. Chemical composition of water in karst plays a crucial role not only in dissolution of karst rocks and deposition but also in ecological processes. The heterogeneous nature of karst aquifers leads to difficulties in predicting groundwater flow and contaminant transport direction and travel times. For its position at the top of karst, epikarst represents the interface between surface and underground. Epikarst ecology, biodiversity and fauna have rarely been systematically studied. The typical absence of enterable passages makes necessary an indirect approach. In this research, epikarst biodiversity in relation to environmental conditions was studied in seven Alpine and Pre-Alpine caves, located at different altitudes, in Slovenia and in Italy: Snežna jama na planini Arto (1556 m a.s.l.), Jama pod Babjim zobom (860 m a.s.l.), Zadlaška jama (300 m a.s.l.) and Pološka jama (500 m a.s.l.), in Slovenian Alps and Pre-alps, and Grotta A del Ponte di Veja (600 m a.s.l.), Covolo della Croce (875 m a.s.l.) and Grotta di Roverè Mille (1005 m a.s.l.) in Lessinian Massif. In these caves, percolating water was monthly monitored for fauna in the period of one year. Temperature, discharge, conductivity and pH were measured at the same time, and water samples for the laboratory analyses of total hardness, concentrations of various ions (calcium, chlorine, nitrate, sulphate and phosphate) and dissolved organic carbon were taken. 66 aquatic and terrestrial, mostly hypogean, species were found. Aquatic fauna was dominant in all caves, with the exception of Covolo della Croce. Caves located at higher elevations harbour less diverse communities. No animals were found when discharge was very low and in correspondence of moonmilk formations. The most abundant and diverse group was Copepoda, with thirteen different species and 776 individuals at different maturity stadia, totally representing 61% of the community (between two and three copepod species per cave in Slovenia and between one and six per cave in Italy). The 62% of copepod species were stygobionts. Some copepod species (e.g. Speocyclops infernus) have wide ecological tolerance to environmental variables, other have more restricted tolerances (e.g. Lessinocamptus insoletus). With regard of copepods, there was a good agreement between the number of observed species and the total number of predicted species, confirming that the sampling method was appropriate and sampling complete. Correlations between the copepod community structure and measured parameters, obtained with Pearson correlation coefficient and principal component analysis (PCA) show different patterns. Presence of copepods was positively correlated with conductivity and dissolved organic carbon in Grotta di Roverè Mille, and with carbonate and nitrate in Pološka jama. In other caves not so high correlations were found between copepod species and measured parameters and between pairs of species. Investigations of the Alpine and Pre-alpine epikarst fauna can help to understand better the ecology of the epikarst fauna and its roles within the large range of different shallow subterranean habitats.
Found in: ključnih besedah
Keywords: Epikarst, Alpine and Pre-Alpine caves, percolating water, speleobiology, fauna.
Published: 31.08.2016; Views: 2690; Downloads: 199
.pdf Fulltext (2,00 MB)

2.
MINERALOGY AND GEOMICROBIOLOGY IN ACTIVE VOLCANIC CAVE ENVIRONMENTS IN CENTRAL AMERICA
Andres Ulloa Carmiol, 2019, doctoral dissertation

Abstract: Recently, the study of mineralogical and geomicrobiological interactions in volcanic caves is gaining relevance, because there are many factors to consider them as Mars analogues for astrobiology and planetary sciences. In addition, sulfuric acid caves have also shown to be an important field of study for the understanding of chemolithoautotrophic metabolic pathways, especially in regard to the biogeochemical cycle of sulfur compounds. Hitherto, sulfur-rich volcanic caves found in Central America were almost unknown to the scientific community. This work presents the mineralogical and microbiological diversity and the potential geomicrobiological links found in active volcanic settings, such as Cueva los Minerales (CMI) and Cueva los Mucolitos (CMU) at Irazú volcano (Costa Rica), and Cueva Hoyo de Koppen (CHK) at El Hoyo volcano (Nicaragua). The volcanic caves at Irazú volcano (Costa Rica) are located in the northwest (NW) foothills of the main crater. These caves became accessible after the partial collapse of the NW sector of the Irazú volcano in 1994, offering the opportunity to investigate in situ active minerogenetic processes. Detailed mineralogical and geochemical analyses were performed to study the speleothems at CMI and CMU. Mineralogical analyses included X-ray diffraction (XRD) and Raman spectroscopy, while geochemical characterization was done using Energy Dispersive X-ray spectroscopy (EDX) coupled to Scanning Electron Microscopy (SEM). In noveladdition, measurements of cave environmental parameters, cave drip water, and a compilation of geochemical analyses of the Irazú volcanic lake (located ca. 150 m above the cave level) and fumarole analyses, were conducted between 1991 and 2014. Forty-eight different mineral phases were identified, mostly rare hydrated sulfates of the alunite, halotrichite, copiapite, kieserite and rozenite groups; thirteen of which are described here, as cave minerals, for the first time, i.e. aplowite, bieberite, boyleite, dietrichite, ferricopiapite, ferrinatrite, lausenite, lishizhenite, magnesiocopiapite, marinellite, pentahydrite, szomolnokite, and wupatkiite. The presence of other novel cave minerals, such as tolbachite, mercallite, rhomboclase, cyanochroite, and retgersite, is likely, but this was not possible to confirm by the various mineralogical techniques employed in this study. It was determined that uplifting of sulfurous gases, water percolation from the Irazú volcanic lake, and hydrothermal interactions with the volcanic host rock are responsible for such extreme mineralogical diversity. Moreover, acidic (pH < 2) viscous biofilms, known as snottites, were observed hanging from both, walls and ceiling, of the caves at Irazú volcano, in close relation with the presence of sulfate minerals. Knowledge about snottites in volcanic caves is scarce, being biofilms present in carbonated rocks the most studied, e.g. at Frasassi and Acquasanta caves (Italy), and Cueva de Villa Luz and Luna Azufre (Mexico). 16S rRNA techniques (with primers for target Bacteria and Archaea), together with bioinformatics analyses, were used to investigate the snottites from CMU and CMI. The results indicated that both prokaryotic groups in the snottites offer a vast metabolic potential to execute various reactions, including redox reactions. The phylogenetic findings revealed that approximately 65% of the identified taxa corresponded to species related to sulfur-oxidizing metabolic pathways (e.g., Leptospirillum, Mycobacterium, Acidithiobacillus and Acidiphilium), while just 0.04% corresponded to sulfur-reducing species (Desulfosporosinus). Since sulfur-oxidizing microorganisms appeared to be dominant in the acidic snottites, induced-gypsum precipitation by changes in micro environmental conditions, is strongly suggested as the path for biomineralization at the studied caves. 34S isotope signature of sulfur minerals presented negative values (from -16.2 to -3.4 ‰), comparable with data obtained...
Found in: ključnih besedah
Summary of found: ...of mineralogical and geomicrobiological interactions in volcanic caves is gaining relevance, because there are many...
Keywords: Volcanic caves, Costa Rica, Irazú, Cueva los Mucolitos, Cueva los Minerales, Nicaragua, Hoyo, Cueva Hoyo de Koppen, mineralogy, sulfur isotopes, hydrated sulfates, active volcano, microbiology, snottites, geomicrobiology, astrobiology, Mars analogue.
Published: 15.04.2019; Views: 980; Downloads: 59
.pdf Fulltext (16,65 MB)

Search done in 0 sec.
Back to top