Xavier Ariño

Factors affecting the weathering and colonization of monuments by phototrophic microorganisms

Phototrophic microorganisms are common inhabitants of monuments. This paper reviews different aspects of their culture, ecology and deterioration mechanisms. Opportunistic species of cyanobacteria and chlorophytes, present in soils and in the air, are commonly found on the surfaces of monuments. Their growth represents a significant input of organic matter to the stone, as estimated through chlorophyll a quantification. Monuments provide unusual niches for the growth of algal communities, as in the case of black sulfated crusts, or endolithic and hypogeal niches, where more specific processes and/or communities occur.

Lichen colonization of the Roman pavement at Baelo Claudia (Cadiz, Spain): biodeterioration vs. bioprotection

This paper describes the effect of lichen colonization on the first century A.D. pavement of the forum at Baelo Claudia, a Roman city located in southern Spain. Lichen colonization is scarce, covering only 13% of the total surface. The rest of the flagstones are mostly uncovered but show strong physico-chemical weathering. The flagstones colonized by lichens do not show weathering. The distribution of the species is influenced by environmental factors, confirming the role of lichens as bioindicators of different habitats. The lichen/sandstone interface shows some weathering, but nevertheless, the protective role of lichens in an aggressive environment is noticeable.

Microbial communities in weathered sandstones: the case of Carrascosa del Campo church, Spain

An integrated study of the microorganisms growing on the weathered sandstone of the church of Carrascosa del Campo (Spain) was carried out. Whilst lichens played only a minor role in colonization, algae and bryophytes were abundant in the sandstone and mortars on the north facade. Although the contribution of algae to deterioration is considered less important, they supported the colonization and development of an allied heterotrophic population of bacteria and fungi, and ultimately, after organic matter decomposition and humification, led to mosses and plants which could have a higher deterioration potential.

Lichens on ancient mortars

Abstract The study of three archaeological sites of southern Spain showed that mortar is a building material easily colonized by a diversity of calcicolous and rather nitrophilous lichens. The interface between lichen and mortar showed an intense chemical activity of the hyphae producing extensive alteration on the surface. The nature and amount of the mortar components greatly influenced the colonizing species and the patterns of alteration.

Colonization and deterioration processes in Roman mortars by cyanobacteria, algae and lichens

The mortars covering some walls of the Roman city of Baelo Claudia (Cadiz, Spain) support an abundant colonization of cyanobacteria, algae and lichens. The distribution of these organisms is closely related to microclimatic parameters. Furthermore, the development, specific composition and biomass of algal cryptoendolithic communities are related to the wall orientation. The effect of these communities on mortar deterioration is discussed.

Cyanobacterial Sulfate Accumulation from Black Crust of a Historic Building.

The cyanobacterium Gloeothece PCC 6909 was cultured in BG 110 medium supplemented with gypsum black crusts removed from the cathedral of Seville, Spain. The sulfate released to the medium due to gypsum dissolution was progressively incorporated into the carbohydrate sheath and used for balanced growth. Therefore, the gypsum black crust served as a continuous source of sulfate for the cyanobacterium, suggesting that gypsum may have a role in the cyanobacteria colonization of blackened monuments in urban environments.

Deterioration of the Elephant Tomb (Necropolis of Carmona, Seville, Spain)

Abstract The Roman Necropolis of Carmona, carved in a calcarenite bed, suffers different deterioration problems. The main alteration processes observed in the tomb walls and roofs are the result of powdering of the rock surface. This is due to the loss of calcite cement, leading to grain individualization and disintegration of the matrix into fine particles. Biological activity both inside and outside the tombs was observed, in some cases preventing disintegration of the calcarenite. The role of phototrophic organisms in the deterioration processes of the Elephant tomb is discussed.

Biological diversity and cultural heritage

In this paper some examples of the development of communities of microorganisms and plants on historic buildings and montiments are shown. When the building stones differ from the surrounding natural substrata, an increase in the biological diversity of the area is produced. In some cases, monuments can come to constitute a true refuge for a few species when the natural habitat is threatened. It is suggested that biological diversity, when it does not represent a threat for the cultural heritage, should be considered worthy of preservation.

Decay of Roman and repair mortars in mosaics from Italica, Spain

A chemical, physical, mineralogical and mechanical characterization has been made of different bedding and repair mortars in mosaics from the Roman town of Italica, Spain. The main cause of deterioration in the superficial mortars is biological attack. In the repair mortars, situated at the deepest levels, all of which are based on Portland cement, the main causes of deterioration are lixiviation, corrosion of metal reinforcements in the concrete, and crystallization of salts in the cement.