Adriano Guido

Commensal symbiosis between agglutinated polychaetes and sulfate-reducing bacteria.

Pendant bioconstructions occur within submerged caves in the Plemmirio Marine Protected Area in SE Sicily, Italy. These rigid structures, here termed biostalactites, were synsedimentarily lithified by clotted-peloidal microbial carbonate that has a high bacterial lipid biomarker content with abundant compounds derived from sulfate-reducing bacteria. The main framework builders are polychaete serpulid worms, mainly Protula with subordinate Semivermilia and Josephella. These polychaetes have lamellar and/or fibrillar wall structure. In contrast, small agglutinated terebellid tubes, which are a minor component of the biostalactites, are discontinuous and irregular with a peloidal micritic microfabric. The peloids, formed by bacterial sulfate reduction, appear to have been utilized by terebellids to construct tubes in an environment where other particulate sediment is scarce. We suggest that the bacteria obtained food from the worms in the form of fecal material and/or from the decaying tissue of surrounding organisms and that the worms obtained peloidal micrite with which to construct their tubes, either as grains and/or as tube encompassing biofilm. Peloidal worm tubes have rarely been reported in the recent but closely resemble examples in the geological record that extend back at least to the early Carboniferous. This suggests a long-lived commensal relationship between some polychaete worms and heterotrophic, especially sulfate-reducing, bacteria.

Serpulid communities from two marine caves in the Aegean Sea, eastern Mediterranean

rossana sanfilippo, antonietta rosso, adriano guido and vasilis gerovasileiou Department of Biological, Geological and Environmental Sciences, University of Catania, Corso Italia, 57, I-95129 Catania, Italy, Department of Biology, Ecology and Earth Sciences, University of Calabria, Via Bucci, cubo 15b, I-87036 Rende, Cosenza, Italy, Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research, 71500 Heraklion, Crete, Greece

The Characterisation of Sedimentary Organic Matter in Carbonates with Fourier-Transform Infrared (FTIR) Spectroscopy

The characterisation of the insoluble macromolecular fraction of sedimentary organic matter preserved in carbonate sediments (also known as kerogen; Durand B, Kerogen: Insoluble Organic Matter from Sedimentary Rocks. Editions Technip, Paris, 1980) allowed for the identification of fossil organisms that were not otherwise preserved.

Morphological and mineralogical evolution of microfossils during the heating process: a contribution to the archaeometric study of ceramics

The role of microfossils for the ceramic paste characterization has been revealed through firing experiment. Ceramic samples were prepared with the clay of Monte San Giorgio (Sicily, Italy), that contains many microfossils that suffered relevant changes in the microstructure and chemical composition during firing temperature. The samples were fired at different conditions according to the presumed ancient techniques. The alteration and/or decomposition of mineral phases with temperature was observed with optical and electron microscopy by monitoring the mineral modifications at different firing conditions. In order to validate our approach on archaeological material, the analyses were performed also on ceramic fragments, furnished by the Ceramics Regional Museum “Antonino Ragona” of Caltagirone. The micropaleontological study, as component of the archaeometric analyses, seems to be a useful archaeothermometry for the evaluation of firing processes and sometimes decisive to distinguish the characteristics of the clay used in a given production.

Micromorphological, geochemical, and diagenetic characterization of sirenian ribs preserved in the Late Miocene paleontological site of Cessaniti (southern Calabria, Italy)

The site of Cessaniti (Vibo Valentia, Italy) has been well known since the 19th century for the richness and good preservation of its Miocene fauna and flora. The sedimentary succession of the site represents a paralic system that evolved toward an open-marine environment recording the Tortonian transgression. The fossil assemblage contains rich invertebrate (corals, bivalves, gastropods, brachiopods, echinoids, benthic and planktonic foraminifers) and vertebrate faunas (proboscideans, rhinoceroses, giraffids, bovids, sirenids, marine turtles, and fish remains). The fossils recovered at the Cessaniti site have a relevant role in phylogenetic studies and paleogeographic reconstructions of Late Miocene environments of the southern Italy. This research is focused on the microstructure and preservation state of the fossil bones. Samples of Metaxytherium sp. bones have been analyzed to understand the diagenetic profile of the bone assemblages that characterizes the taphonomic history of the Cessaniti site. The analyses provided a comprehensive account of how bone mineral (bioapatite) has been altered and demonstrated that the post-burial processes did not significantly affect the micromorphological and biogeochemical features of the bones. The excellent preservation state of the bones strengthens the importance of the Cessaniti site for studies of the Mediterranean Miocene vertebrate fauna.

Importance of Rare Earth Element Patterns in Discrimination Between Biotic and Abiotic Mineralization

Rare earth element (REE) patterns have been used to discuss the origin of rocks and minerals and the evolution processes that occurred during their formation (Goldschmidt 1954; Henderson 1996).

SEM morphological studies of carbonates and the search for ancient life on Mars

Next space missions will investigate the possibility of extinct or extant life on Mars. Studying the infrared spectral modifications, induced by thermal processing on different carbonate samples (recent shells and fossils of different ages), we developed a method able to discriminate biogenic carbonates from their abiogenic counterparts. The method has been successfully applied to microbialites, i.e. bio-induced carbonates deposits, and particularly to stromatolites, the laminated fabric of microbialites, some of which can be ascribed to among the oldest traces of biological activity known on Earth. These results are of valuable importance since such carbonates are linked to primitive living organisms that can be considered as good analogues for putative Martian life forms. Considering that the microstructures of biogenic carbonate are different from those of abiogenic origin, we investigated the micromorphology of shells, skeletal grains and microbialites at different scale with a scanning electron microscope. The results show that this line of research may provide an alternative and complementary approach to other techniques developed in the past by our group to distinguish biotic from abiotic carbonates. In this paper, we present some results that can be of valuable interest since they demonstrate the utility for a database of images concerning the structures and textures of relevant carbonate minerals. Such data may be useful for the analysis of Martian samples, coming from sample return missions or investigated by future in situ explorations, aimed to characterize the near-subsurface of Mars in search for past or present life.

Microbial Biomineralization in Biotic Crusts from a Pleistocene Marine Cave (NW Sicily, Italy)

ABSTRACT Biotic crusts occurring in the Early Pleistocene Rumena Cave, in NW Sicily, have been analyzed from a geomicrobiological point of view. The crusts consist largely of scleractinians and of subordinate bryozoans and serpuloideans, all typical of submarine cave biota. Encrustations document a blind cave in a shadowed setting, or possibly below the fair weather swell zone. Autochthonous and, subordinately, detrital fractions were observed within the skeletal framework of biotic crusts. The syndepositional lithified fraction occurs mainly as very fine-grained laminations. Clotted peloidal and aphanitic (structureless) textures occur in the micrites as well. Autochthonous micrite is always associated with a significant amount of organic matter remains. In caves from the Plemmirio area in SE Sicily, the autochthonous microbial micrite, occurring in the bioconstructions, contains bacterial lipid biomarkers, including abundant compounds derived from sulfate-reducing bacteria. It is likely that a similar microbial mediation was involved in the formation of the autochthonous micrite present in the biotic crusts of the Rumena Cave.

Role of autochthonous versus detrital micrite in depositional geometries of Middle Triassic carbonate platform systems

Middle Triassic platforms (Formazione di Contrin, Upper Anisian) in the Italian Dolomites, southern Alps, record large changes in carbonate production and depositional geometry. The changes include variation in the abundance of detrital micrite, i.e., allochthonous calcareous mud, relative to the autochthonous micrite, which formed in situ and was syndepositionally lithified. Carbonate factory dynamics controlled the geometry of the clinostratified slope units and were probably associated with changes in oxygenation. Early Anisian low-relief platforms were followed by late Anisian, high-relief buildups, associated with basinal dysoxic-anoxic environments. The geometric evolution of the platform slopes records a progressive increase in the dip angle of clinostratifications, matched by a deepening evolution of the basinal environments. At the same time, the slope sediments record a gradual change from loose detrital micrite, characterizing the lower portion, to autochthonous micrite, dominating the upper part and recording massive syndepositional lithification. The development of the autochthonous micrite was associated with the preservation of significant amounts of organic matter. This sharp increase in automicrite formation was probably induced by a rapid change from oxic to suboxic conditions in the carbonate slope and margin environments, while anoxic conditions developed in the adjacent organic-rich basin (Moena Formation). The low oxygen level promoted the preservation of organic matter and the activity of sulfate-reducing bacteria, which in turn induced in situ deposition of autochthonous micrite through biomediated processes. This pervasive early cementation and lithification induced the development of steep platform slopes. The conceptual model distilled from this Middle Triassic case can support the interpretation of analogous buildups where the skeletal framework is subordinate to the micrite component.

Cryptic serpulid-microbialite bioconstructions in the Kakoskali submarine cave (Cyprus, Eastern Mediterranean)

The biostalactites from the Kakoskali cave in Cyprus represent a new example of the complex biotic relationships between skeletal organisms and microbial communities in building bioconstructions of cryptic marine environments. Biostalactites are mainly constituted of polychaetes of the family Serpulidae and, to a lesser degree, foraminifers and bryozoans. Within the skeletal framework of these organisms, two types of microcrystalline calcite (micrite) have been recognized: autochthonous and detrital micrite. The autochthonous fraction is syndepositionally lithified and occurs as clotted peloidal and, subordinately, aphanitic (structureless) textures, suggesting the presence of heterotrophic microbial activities thriving on decaying metazoan organic matter. This fraction is limited to the protected portions of the bioconstructions, especially in the inner and lower parts. The presence of iron and manganesiferous oxidizing bacteria is suggested by the deposition of ferromanganesiferous crusts and Frutexites-like structures. These microbial-induced biomineralizations are the main evidence of carbonatogenetic and Fe–Mn, autotrophic and chemoheterotrophic, bacterial activities. The Kakoskali cave is frequently visited by divers who, during their immersions, resuspend the fine bottom sediment, which later covers the surface of the bioconstructions, disturbing the delicate equilibrium of the biotic association. This perturbation, which is also caused by strong waves and currents, during winter months, reflects on the bioconstruction morphologies, community composition, and colonization pattern. Bioconstructions exhibit an upper smooth surface, produced by few taxa (e.g., polychaetes, foraminifers), hosting a low number of living individuals, and a lower comparably rough surface, colonized by a more abundant community showing a higher species richness. The ratio surface roughness/smoothness is related to micrite sediment type: the upper part is mainly characterized by loose detrital micrite while the internal and lower parts by syndepositional cemented autochthonous micrite.