585

BIODETERIORA TION OF THE TEMPLE OF SEGESTE (SICILY)

MONTE,M. and FERRARI, R.

C.N.R. - Centro di studio sulle cause di deperimento e sui metodi di conservazione delle Opere d'Arte (Centre for studying the causes of

deterioration and methods of conserving works of art) : Via Monte d'Oro, 28 - 00186 Rome (Italy)

INTRODUCTION

Alterations in the upper layer of stone are, above all, the result of the physical-chemical changes caused by solar radiation and humidity. All the deterioration phenomena are triggered by these two factors, including those caused by biological agents (Monte 1991A). Alteration morphologies connected with the development of living organisms are very different and their biological matrix is not always recognisable in them (Nonnal 1/88).

In Italy, lichens are the most widespread factor of biodeterioration on stone exposed to the open air; on archaeological ruins in Lazio and Sardinia (Nimis et al. 1987; Tretiach et al. 1991 ; Monte and Tretiach 1992) the presence of more than 300 different species has been observed. In these areas, a great number of lichen species are found fonning a dense coverage, above all where the effects of industrialization and motor traffic are not directly felt. It is a well-known fact that lichens are extremely sensitive to some kinds of atmospheric pollutants, so that they cannot survive in densely built-up and highly industrialized areas (Seaward 1977). However, the species have different tolerance to pollutants: this has made it possible to standardize methods of evaluating the purity of air, by identifying the species that are present (Amman 1987). Since they react directly to environmental conditions, lichens may also be used as environmental bioindicators. Each single species, in fact, can live only within a precise range of pH values, humidity, light and quantity of nitrogenous substances, with the result that by observing the species present and by detennining their ecological needs, it is possible to draw conclusions about some environmental

parameters that condition the lithic artefact's state of conservation (Monte 1991 B). Little is known about the amount of damage that lichens can produce on stone, even if the mechanisms are known. Emission of some acidic metabolites and the chelation effect linked to them lead to corrosive

phenomena (Ascaso et al. 1982). Damage resulting from the mechanical action of the thallus is due to the depth of its penetration into the

stone and the continual dilation and contraction that the thallus undergoes following states of greater or

lesser hydration (Fry 1924). Some authors have put forward the suggestion that slow-growing species cause such negligible damage that they can even be thought of as a protection against the aggression of acid rain (Lallement &

Deruelle 1978). These observations fonn the basis of the controversies about the usefulness of carrying out operations to eliminate the lichens by means of biocidal substances. Since it is well-known the different species have a different alteration ability (Seaward 1988), it is necessary to carry out systematic studies on the lichenic flora and vegetation found on various types of stone under different environmental conditions. Knowledge thus acquired must be considered propedeutic for research aimed at evaluating the degree of alterative power possessed by the various species in determined environmental conditions and on

artefacts varying from the chemical and structural point of view. This will make it possible to carry out interventions to eliminate lichens, in a non-indiscriminate manner, so as to safeguard both the artefact and those species that would prove to be harmless. Very often, in fact, monuments are host to species

that have great naturalistic value and can provide additional interest to the work. The purpose of this work is to identify the lichens that grow on the surface of the Temple of Segesta, in

the province of Trapani (Sicily) (photo n° 1). The temple was erected in the 5th century BC and consists of 14 columns on the long sides and 6 on the front and rear fayades. The columns are 9.6 m. high and have a diameter of 1.95m. at the base. Built of

very porous calcareous stone, it is in a good state of preservation, although interior structures are completely absent. Its position is outside the walls of the ancient city of Segesta, at a height of 305m.

and at a distance of about 5 kms from the sea.

586

DATA AND METHODS

The floristic study involved identifying all the species of lichen present, both on all 4 fayades, on the columns themselves and also on the bases of the columns. For identification purposes, the identification key proposed by Nimis et al. (1987) was followed, as well as the studies of the Mediterranean coast

lichen flora by Navarro-Rosines et Roux (1994, 1995). In order to identify the species, besides surveying the morphological and structural characteristics of the thallus, carried out in field studies and by microscope, the specific substances of the various species were also observed by means of microchemical tests, such as:

- K: solution saturated with KOH - C: solution saturated with Ca (C10)2 - P: alcohol solution at 5% paraphenylendiamine

To determine the ecological needs of the species, indices of nitrophytism (nitrogen), hygrophytism (water) and photophytism (light) proposed by Wirth (1980) were referred.

- Nitrophytic Index (NJ 1: anitrophytic; 2: moderately nitrophytic; 3: rather nitrophytic; 4: very nitrophytic; 5: extremely

nitrophytic. - Hygrophytic Index (HJ 1: extremely hygrophytic; 2: very hygrophytic; 3: rather hygrophytic; 4: mesophytic; 5: rather xerophytic; 6: very xerophytic. - Photophytic Index (LJ 1: very skiophytic; 2: rather skiophytic; 3: moderately skiophytic; 4: rather photophytic; 5: very photophytic.

RESULTS

In table 1, the list of lichen species observed from each fac;ade, on the columns and on the column bases, is given.

Table n°1: LICHENS PRESENT ON THE SURFACE OF THE TEMPLE OF SEGESTA AT THE VARIOUS EXPOSURES, ON THE COLUMNS AND ON THE COLUMN BASES*

-------------------------------------------------- ----------------------------------------------------Column Column base

species North South East West North South East West Horizontal

-;~~;,~-,:~~,~~~,;~;,~\~~---------~~~-~------------~~--~ ------~.-----------------+------------------------------------------++

( "aloplaca /avaresit111tJ + ++ + + ('a /oploca 11m'm ia;w + +++ + + H111dlia nivalis + + + ++ ( "a/op!tJu1 aylrocwptJ . /5picilia calcurea /loccel/a phycopsis ++ liaglielfoa ptm11igf'rt1 l 'er11tearia 11i~rl!sce11'· l.<'cania spadfceu I ·erntcuria calcisecla /,ecanora dispersu l .ecanora 11111ra/is

var. versicvlor ( 'a/op/aca cilrina Ca/op laca utirw11ia ( 'a/op/acaferrurii ( 'a1illaria lenliwlaris ('tJ/oplaca 1eicholv1a Candelm·i<'lla 111e;lians .\"rmlhoria calcicola Caloplaca lac/ea

* abundant: +++ medium: ++

~+ +++ + ++ ++ ++ ++ ++

+

++

scarce: +

++ + +++ +

+++ +

+ ++ + + + +++ -+++ ++ ++ ++ ++

I< +

R

I~

+ ++

+ I~

rare: R

+++ ,.

+ +++

++

+ +

+ +

+-'-

587

The following situation has been observed: On the columns:

- on the part exposed to the north, the species Dirina massiliensis predominates. Above 2 m. from the ground, this species is associated with the fruticose species Roccella phycopsis. - no lichens are to be found on the south.

- on the east, the species Caloplaca navasiana predominates and the species Lecania spadicea is found in the crevices.

- on the west, the species Dirinia massi/iensis predominates. The species Bagliettoa parmigera, Veffucaria nigrescens and Lecania spadicea are to be found, showing medium coverage.

On the column bases, vertically:

- the species Bagliettoa parmigera is prevalent on the north.

- the greatest coverage on the south comes from the species Lecania spadicea and Caloplaca erytrocarpa.

- the species Dirina massiliensis, Bagliettoa parmigera, Lecania spadicea, Veffucaria calciseda and Catillaria lenticularis are present on the west with medium coverage.

On the column bases, horizontally:

- the horizontal part of the Temple base is almost entirely covered by thalli of Veffucaria nigrescens, Caloplaca erytrocarpa and, to a lesser extent, Calplaca lactea. Eutrophyzation of the building, caused by the flow of visitors, has made the development of nitrophylous species possible, such as Calplaca citrina, Caloplaca teicholytc, and Candelariella medians, in some places only.

Under the surface of the stone

Microscopic algae have been found under the surface of the stone, in crevices at a depth of about 4 mm. (photo n°2 ).

The flake of which the photograph was taken was obtained by removing a piece of stone without any cracks, so that the light must penetrate through the texture of the intact stone. It is evident that the light which does penetrate, however weak it may be, is sufficient to trigger the processes of photosynthesis.

CONCLUSION

From observations in the field and from optical microscope analyses, it was shown that the limestone biodeterioration of the Temple is basically caused by lichens. A massive presence of snails was also observed (photo n° 3 ) . These are an integral part of the ecosystem; they feed on the lichens' thallus and are the most important agent for spreading the spores. The crustose species Dirina massiliensis (photo n° 4 ) is the most widespread, covering 70% of the column surface exposed to the north and west. The thalli, which have a white cretaceous-farinos appearance owing to the presence of oxalates, run together and take on the appearance of a patina that covers the surface almost entirely. The apothecia, which are very numerous, have a black disc, often extremely pruinose. This species is considered to be one of the most aggressive towards stone (Seaward & Giacobini 1989), since it can lead to great alterations in the lithic surface. From a study on treatments to eliminate lichens, carried out by our Institute, the results of which have not yet been published, it has been proved that this species is one of the most resistant to the action of biocides. The ecological indices

of the species are: N =1 ; L= 2; H = 4. on the columns and bases exposed to the east, the species Caloplaca navasiana is the most widespread

(photo n°s ). It is a new species, only recently described as a characteristic of the Mediterranean coasts

on porous calcareous substrata (Navarro-Rosines et Roux, 1995). It has a thin thallus, areolate-fissured, of a whitish colour, owing to the absence of antrochinones and is therefore negative to reagent K. The

apothecia are orange in colour, the spores are very long and polar-diblastic: the ratio between length and

width is greater than 2. This alophylous, heliophylous and moderately nitrophylous species has been

found on the calcareous cliffs of Spain, Greece and Cyprus.

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The species Lecania spadicea (photo n° 6 ) is widespread and is to be found, above all, in crevices where the particle deposit has enriched the substratum with nitrogen substances. It is a highly nitrophylous species and has a dark thallus with well- developed lobes and apothecia with a pruinose, reddish disc. The strong decohesion of the substratum that has been found under the thalli of Lecania spadicea makes it likely that its alteration action is far from negligible. The species' ecological indices are: N = 2-3; H = 5-6; L = 4-5. Among the endolithic lichens, the species Bagliettoa parmigera (photo n° 7 ) is found in abundance on the column bases exposed to north and west. The thallus of this species is the same colour as the substratum, because it is covered by a thin layer of calcium carbonate deposited on its external surface. It can be distinguished from the stone by the outline of the thallus and by its fruit-bearing bodies. These are perithecia which, at the end of their life cycle, release spores, die and leave small depressions on the surface of the calcareous stone. These depressions take on the appearance of a characteristic alveolization called "pitting". The elimination of endolithic lichens, which also give rise to strong alteration phenomena, is generally inadvisable. In fact, the removal or death of the lichens also causes crumbling in the lithic stratum into which the thallus has penetrated. The ecological indices of the species are: N =1; H = 2-3; L = 3-4. The species Caloplaca erytrocarpa (photo n° 8 ) is found only on the column bases with a southern exposure and on horizontal surfaces. It has a white areolate-fissured thallus; the apothecia have a flat rust-red coloured disc. The damage this species can cause to stone is not known. The ecological indices are: N = 1-2; H = 5; L = 4-5. On the steps of the Temple in a horizontal position there is also an abundant presence of the species Verrucaria nigrescens, whose black thallus, provided with perithecia, covers very extensive surfaces (photo n° 9 ). It does not appear to cause great chemical and/or physical alteration phenomena to the stone, even if the aesthetic reading of the work of architecture is greatly compromised by the large extent of the dark staines of the thalli.

BIBLIOGRAPHY -Ammann K., Herzig R., Libendoerfer L., Urech M., 1987. Multivariate correlation of deposition data of 8 different air pollutants to lichen data in a small town in Switzerland. Advances in Aerobiology, 51, 401-406 - Ascaso C , Galvan J. & Rodriguez-Pascual C., 1982. The weathering of calcareous rocks by lichens. Pedobiologia, 24, 219-229

- Fry E. J., 1924. A suggested explanation of the mechanical action of lithophytic lichens on rocks (shale). Ann. Bot. (London), 38, 175-196

- Lallement R. & Deruelle S., 1978. Presence de lichens sur Jes monuments en pierre. Nuisance ou protection. International Symposium UNESCO-RILEM "Deterioration and protection of stone monuments, Paris, 4.6 - Monte M., 1991A. Multivariate analysis applied to the conservation of monuments: lichens on the Roman aqueduct Anio Vetus in S. Gregorio. International Biodeterioration, 28, 133-150

- Monte M , 19918. La lichenologia applicata a/la conservazione dei monumenti in pietra esposti a/l'aperto: problemi e prospettive. Atti del Convegno "Le pietre nell'architettura: strutture e superfici", Bressanone, eds G. Biscontin and D. Mietto, Progetto Editore, Padova, 287-298

- Monte M., Tretiach M., 1992. Ucheni sui nuraghi: un cantiere di ricerca. Atti del convegno "Scienza dei materiali e beni culturali. Esperienze e prospettive nel restauro delle costruzioni nuragiche", Cagliari, 1990, 73-81 - Navarro-Rosines P., Roux C., 1994. Le Calop/acetum tavaresianae Roux et Nav.-Ros. ass. nov., une association lichenique saxicole-calcicole, halophile. Nova Hedwigia, 59, 255-264

- Navarro- Rosines P. et Roux C., 1995. Ca/oplaca navasiana Nav.-Ros. et Roux sp. nov., espece nouvelle de lichen du littoral mediterraneen. Cryptogamie, Bryol. Lichenol., 16 (2), 89-97

- Nimis P.L., Monte M., Tretiach M., 1987. Flora e vegetazione lichenica di aree archeologiche de/ Lazio. Studia Geobotanica, 7, 3-161 - Normal 1/88, 1990. Alterazioni macroscopiche dei materiali /apidei. C.N.R. - ICR, 1-36 - Seaward M.R.D., 1977. Uchen Ecology. Academic Press, London, 1-436

- Seaward M.R.D., 1988. Uchen damage to ancient monuments: a case study. Lichenologist, 20(3), 291_295 - Seaward M.R.D. & Giacobini C., 1989. Oxalate encrusta-tion by the lichen Dirina massiliensis forma sorediata and its role in the deterioration of Works of Art. Proceedings of Inter. Symposium • The oxalate films: origin and significance in the conservation of Works of Art", Centro CNR "Gino Bozza", Politecnico di Milano, 21 5_

219 - Tretiach M., Monte M. & Nimis P.L., 1991 . A new hygrophytism index for epilithic lichens developed on b If Nuraghes in NW Sardinia. Botanika Chronika, eds D. Phitos & W. Greuter, University of Patras, Greece,

953_;;; IC

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The snails are tile most important agent for spreading the spores of lichens

590

591

The endolithic lichen Bagliettoa parmigera is found on the column bases exposed to north and west

The species Ca/op/aca erytrocarpa is found on the column bases with a southern

exposure and on horizontal surfaces