Mauro Brilli

Isotope Geochemistry of Caliche Developed on Basalt

Enormous variations in oxygen and carbon isotopes occur in caliche developed on < 3 Ma basalts in 3 volcanic fields in Arizona, significantly extending the range of δ18O and δ13C observed in terrestrial caliche. Within each volcanic field, δ18O is broadly co-variant with δ13C and increases as δ13C increases. The most 18O and 13C enriched samples are for subaerial calcite developed on pinnacles, knobs, and flow lobes that protrude above tephra and soil. The most 18O and 13C depleted samples are for pedogenic carbonate developed in soil atmospheres. The pedogenic caliche has δ18O fixed by normal precipitation in local meteoric waters at ambient temperatures and has low δ13C characteristic of microbial soil CO2. Subaerial caliche has formed from 18O-rich evapoconcentrated meteoric waters that dried out on surfaces after local rains. The associated 13C enrichment is due either to removal of 12C by photosynthesizers in the evaporating drops or to kinetic isotope effects associated with evaporation. Caliche on basalt lava flows thus initially forms with the isotopic signature of evaporation and is subsequently over-layered during burial by calcite carrying the isotopic signature of the soil environment. The large change in carbon isotope composition in subsequent soil calcite defines an isotopic biosignature that should have developed in martian examples if Mars had a “warm, wet” early period and photosynthesizing microbes were present in the early soils. The approach can be similarly applied to terrestrial Precambrian paleocaliche in the search for the earliest record of life on land. Large variations reported for δ18O of carbonate in Martian meteorite ALH84001 do not necessarily require high temperatures, playa lakes, or flood runoff if the carbonate is an example of altered martian caliche.

a new foodweb based on microbes in calcitic caves: The Cansiliella (Beetles) case in northern italy

inTrOducTiOn In air-filled cave and karst habitats, troglobites and troglophiles rely on an influx of allochthonous (surface-derived) organic matter from dripwaters or sheetflow on moist cave-wall surfaces. This habitat type is referred to as the cave hygropetric (Sket, 2004). Hydrological isolation for some cave hygropetric habitats may restrict the influx of organic matter, making a habitat nutrient-limited overall. Consequently, food limitation over extended periods of time has served as a major driver for evolutionary adaptation for troglobites (e.g., Sket, 2004). One highly evolved, troglobitic beetle, Cansiliella servadeii Paoletti 1980 (Coleoptera: Leptodirini, formerly Bathysciinae), has been found at a depth of ~450 m below the surface in Grotta della Foos, northeastern Italy. Paoletti M.G., Beggio M., Dreon A.L., Pamio A., Gomiero T., Brilli M., Dorigo L., Concheri G., Squartini A., Summers Engel A. 2011. A new foodweb based on microbes in calcitic caves: the Cansiliella (Beetles) case in Northern Italy. International Journal of Speleology, 40(1), 45-52. Tampa, FL (USA). ISSN 0392-6672. DOI: 10.5038/1827-806X.40.1.6

Comparative microbial community composition from secondary carbonate (moonmilk) deposits: implications for the Cansiliella servadeii cave hygropetric food web

The microbial diversity of moonmilk, a hydrated calcium carbonate speleothem, was evaluated from two Italian caves to provide context for the food web of highly-specialized troglobitic beetles, Cansiliella spp. (Leptodirinae), with distinctive carbon and nitrogen isotope values indicative of a novel food source. The moonmilk and associated percolating waters had low to no extractable chlorophyll, with an average organic C:N ratio of 9, indicating limited allochthonous input and a significant contribution from microbial biomass. The biomass from moonmilk was estimated to be ~10 4 micro- and meiofaunal individuals per m 2 and ~10 7 microbial cells/ml. Proteobacteria dominated the 16S rRNA gene sequences retrieved from the moonmilk from both caves. The distribution of other proteobacterial classes and phyla in the moonmilk were statistically similar to each other, even though the two caves are geographically separated from each other. Comparing the moonmilk gene sequences to sequences from previously described environmental clones or cultured strains revealed the uniqueness of the moonmilk habitat, as ~15% of all of the moonmilk sequences were more closely related to each other than to sequences retrieved from any other habitat. However, comparative analyses confirmed that as much as ~34% of the clones sequences were also closely related to environmental clones and cultured strains derived from soil and freshwater habitats, which is likely due to the fact that the putative inoculation source for the moonmilk bacterial communities is from overlying soil and percolating fluids from the surface. Prior to our studies of Cansiliella spp., moonmilk has not been considered a food source for cave animals. Our findings provide unique insight into moonmilk microbial diversity that could reveal the underpinnings of the moonmilk carbon and nitrogen cycle that influences the isotopic composition and the morphological adaptations of the troglobitic beetles associated with the moonmilk. calcium carbonate; microorganisms; food web; nitrogen cycling; beetles

A unique midgut-associated bacterial community hosted by the cave beetle Cansiliella servadeii (Coleoptera: Leptodirini) reveals parallel phylogenetic divergences from universal gut-specific ancestors

BackgroundCansiliella servadeii (Coleoptera) is an endemic troglobite living in deep carbonate caves in North-Eastern Italy. The beetle constantly moves and browses in its preferred habitat (consisting in flowing water and moonmilk, a soft speleothem colonized by microorganisms) self-preens to convey material from elytra, legs, and antennae towards the mouth. We investigated its inner and outer microbiota using microscopy and DNA-based approaches.ResultsAbundant microbial cell masses were observed on the external appendages. Cansiliella’s midgut is fully colonized by live microbes and culture-independent analyses yielded nearly 30 different 16S phylotypes that have no overlap with the community composition of the moonmilk. Many of the lineages, dominated by Gram positive groups, share very low similarity to database sequences. However for most cases, notwithstanding their very limited relatedness with existing records, phylotypes could be assigned to bacterial clades that had been retrieved from insect or other animals’ digestive traits.ConclusionsResults suggest a history of remote separation from a common ancestor that harboured a set of gut-specific bacteria whose functions are supposedly critical for host physiology. The phylogenetic and coevolutionary implications of the parallel occurrences of these prokaryotic guilds appear to apply throughout a broad spectrum of animal diversity. Their persistence and conservation underlies a possibly critical role of precise bacterial assemblages in animal-bacteria interactions.

GROTTA ROMANELLI (SOUTHERN ITALY, APULIA): LEGACIES AND ISSUES IN EXCAVATING A KEY SITE FOR THE PLEISTOCENE OF THE MEDITERRANEAN

Grotta Romanelli, located on the Adriatic coast of southern Apulia (Italy), is considered a key site for the Mediterranean Pleistocene for its archaeological and palaeontological contents. The site, discovered in 1874, was re-evaluated only in 1900, when P. E. Stasi realised that it contained the first evidence of the Palaeolithic in Italy. Starting in 1914, G.A. Blanc led a pioneering excavation campaign, for the first-time using scientific methods applied to systematic paleontological and stratigraphical studies. Blanc proposed a stratigraphic framework for the cave. Different dating methods (C 14 and U/Th) were used to temporally constrain the deposits. The extensive studies of the cave and its contents were mostly published in journals with limited distribution and access, until the end of the 1970s, when the site became forgotten. In 2015, with the permission of the authorities, a new excavation campaign began, led by a team from Sapienza University of Rome in collaboration with IGAG CNR and other research institutions. The research team had to deal with the consequences of more than 40 years of inactivity in the field and the combined effect of erosion and legal, as well as illegal, excavations. In this paper, we provide a database of all the information published during the first 70 years of excavations and highlight the outstanding problems and contradictions between the chronological and geomorphological evidence, the features of the faunal assemblages and the limestone artefacts.

Geochemical study of travertines along middle-lower Tiber valley (central Italy): genesis, palaeo-environmental and tectonic implications

Several travertine deposits dating to the Pleistocene outcrop along the Tiber valley between Orte and Rome. Mineralogically, they are mainly composed of calcite; various lithofacies (stromatolitic, phytoclastic, and massive) were identified and relatively wide ranges of carbon (δ13C −8.11 to +11.42‰ vs. VPDB) and oxygen (δ18O +22.74 to +27.71‰ vs. VSMOW) isotope compositions were measured. The isotope and chemical compositions of water and free gases, in some cases associated with the travertines, were also measured. Carbon isotope data show that several samples fall in the typical range of thermogenic travertine, i.e., linked to the addition of deep inorganic CO2. The oxygen isotope composition of the springs associated with the travertine deposits points to travertine precipitation by slightly thermal water of meteoric origin. In general, these travertines are in association with, or close to, mineralised groundwaters (with slightly acidic pH, low thermalism, and enrichment in sulphates or sodium chloride) and rich CO2 gas emissions, the origin of which may be linked to decarbonation reactions. The travertine bodies are locally connected with crustal structural lineaments favouring the circulation of ascending deep CO2-rich fluids. Conversely, some samples show isotopic connotations of meteogenic deposits, representing travertines formed mainly from soil biogenic or atmospheric carbon dioxide generally present in shallow groundwater or surface water. According to their morphology and isotope data, these travertines may be attributed to the sedimentary environment of waterfalls. These new geochemical and morphological data are integrated with those already available in the literature regarding the study area and contribute to shedding light on palaeo-environmental conditions in western-central Italy during the Quaternary.

Natural sources of carbon dioxide and methane from the fluvio-lacustrine sediments of the Fucino Plain (Central Italy): evidence from stable carbon isotopes

The present investigation focused on the origin of CO2 and CH4in the soil gas and two gas vents present in the Fucino plain, a tectonicallyactive intramontane depression of central Italy. The soilgases have concentrations of CO2 ranging from 1 to 10% and CH4 inthe order of a few parts per million. Using carbon isotopes, it waspossible to identify two different sources of CO2 in the soil gas: biogenicCO2 (d13CCO2~ –20‰) produced in the fluvio-lacustrine sedimentsof the plain and CO2 produced from CH4 oxidation in soil(d13CCO2 –34/–38‰). The two gas vents yield CO2 contents of 2.63and 15.33% and CH4 of 94.7 and 8.5%. In the CH4-dominated gasvent, the carbon isotopes of methane (d13CCH4 = –64‰) point to agas of microbial origin. The other gas vent, with a d13CCH4 of–52.8‰, may be affected by a microbial oxidation process.