Beatriz Cámara

Ignimbrite textural properties as determinants of endolithic colonization patterns from hyper-arid Atacama Desert

This study explores the photosynthetic microbial colonization of rhyolitic ignimbrites in Lomas de Tilocalar, a hyper-arid region of the Atacama Desert, Chile. Colonization appeared in the form of a green layer a few millimeters beneath the ignimbrite surface. Some ignimbrite rocks revealed two distinct micromorphological areas of identical mineralogical and chemical composition but different textural properties. According to texture, colonization patterns varied in terms of the extension and depth of colonization. The diversity of photosynthetic microorganisms was assessed by denaturing gradient gel electrophoresis (DGGE) of the 23S rRNA gene and by generating clone libraries of the 16S rRNA gene. We observed a low diversity of photosynthetic microorganisms colonizing the ignimbrite microhabitat. Most rRNA gene sequences recovered greatly resembled those of Chroococcidiopsis hypolith clones from arid deserts. These results point to highly restrictive conditions of the hyper-arid Atacama Desert conditioning the diversity of cyanobacteria, and suggest that microbial colonization and composition patterns might be determined by the microscale physico-chemical properties of the ignimbrite rocks.

Anthropic effect on the lichen colonization in building stones from cultural heritage

In this study the effect of human urine on lithobiontic microorganisms colonizing stone materials from the cultural heritage was evaluated in situ by means of a field experiment in a historic quarry (Reduena dolostone quarry, Madrid, Spain). With this experiment, it was possible to assess the effect of this bioproduct when interacting with the existing lithobiontic microbial community at the most real conditions. The application of the bioproduct was performed by directly spraying onto the rock surface of the quarry front with abundant lichen colonization during 8 weeks (one application per week). After the application, the structure of Verrucaria nigrescens lichen thalli and the ultrastructure of their algal and fungal cells components resulted to be affected. The upper cortex of the lichen thalli was particularly affected, with damage-like fungal cells, and even in some cases, disappeared, leaving unprotected and exposed algal cells to environmental conditions.

Biodeterioration of marble in an underwater environment

This study examines the deterioration of geomaterials used throughout history that today may be found lying on the ocean floor. Submerged archaeological sites including cargoes from shipwrecks or ancient city ruins have been a topic of interest from a perspective of in situ musealization, as a way of making underwater cultural heritage accessible to the public. In an experimental study conducted at an underwater archaeological site in the Bay of Cádiz (SW Spain), we subjected two types of marble (Carrara and Macael) to three conditions to which submerged archaeological objects are often exposed: full exposure to the water column, natural processes of burial and unearthing, or permanent burial. After an 18-month study period, the factor found to mostly affect these materials was their biological colonization. This factor was assessed by estimating total surface biocover and the rate of surface biocolonization, and also through the identification of skeletons and associated alteration forms by light microscopy, and scanning electron microscopy (SEM). Biofouling and bioerosion were the main causes of biodeterioration and dependent on the position of the marble specimens in the seawater. The response of both materials was similar, though dolomite crystals in the Carrara marble acted as a protective barrier against actively penetrating microorganisms. These investigations have allowed the study of tracers left by epilithic encrusting organisms and endolithic bioeroders on marbles intentionally exposed to seawater, providing new insights to the understanding of the biodeterioration processes occurring in cultural heritage stones, with significant implications when they are part of underwater archaeological remains.