10.6092/issn.1973-9494/7122
I manufatti lapidei esposti all’aperto sono sottoposti a processi naturali di deterioramento, dovuti a fattori di natura fisica, chimica e biologica. I macro e micro sistemi biologici (per esempio semi, insetti, alghe, muschi, funghi e batteri) possono causare il deterioramento dei materiali lapidei. Nel Febbraio del 2014 è stato effettuato uno studio sullo stato di conservazione della Fontana dei due Draghi, Palermo, durante il quale sono state individuate diverse aree interessate da colonizzazione biologica, sia all’interno della fontana e sia sulle statue decorative. Il monumento rappresenta un substrato di crescita eccellente per lo sviluppo di microorganismi e di organismi che necessitano di un continuo supporto di acqua. Inoltre, l’irradiamento solare diretto promuove lo sviluppo di organismi autotrofi , briofite oltre a diversi generi microbici responsabili dei fenomeni di pigmentazione, alterazioni cromatiche, efflorescenze. Dopo la colonizzazione autotrofi ca, molti organismi trovano l’habitat ideale anche durante il periodo invernale, incluse due specie di gastropodi e due specie di Hemiptera, onnivori, una specie di Collembola, principalmente fungivoro. Questo studio interdisciplinare ha permesso di identificare differenti comunità biologiche, fornendo informazioni utili per un futuro progetto di conservazione preventiva della fontana e il suo ambiente circostante.
application/pdf
1973-9494
7122
2
en
Silvana Lo Giudice
Conservation Science in Cultural Heritage
micro and macro-organisms
Biological Macro and Micro Systems Co-existing in the “Fountain of the Two Dragons”, Palermo
Text.Serial.Journal
https://conservation-science.unibo.it/
15
Articles
2017-06-01
2017-07-04
2017-06-01
2017-09-04
95-107
CSCH
Silvana Lo Giudice
2015
10.6092/issn.1973-9494/7122
95
Salvare Palermo Fondazione Onlus, Palermo
1973-9494
2
micro and macro-organisms
en
107
Biological Macro and Micro Systems Co-existing in the “Fountain of the Two Dragons”, Palermo
https://conservation-science.unibo.it/article/download/7122/6832
15
B     IOLOGICAL MACRO AND MICRO SYSTEMS CO-EX-
      ISTING IN THE “FOUNTAIN OF THE TWO DRAGONS”,
      PALERMO


    Enza Di Carlo, Giovanna Lombardo, Giovanna Barresi, Barbara Manachini,
    Franco Palla*8
    Laboratorio di Biologia e Biotecnologie per i Beni Culturali, STEBICEF, Università
    degli Studi di Palermo, Italy
    Gaetano Corselli D’Ondes, Silvana Lo Giudice
    Salvare Palermo Fondazione Onlus, Palermo, Italy


    Keywords: fountain; stone biodeterioration; micro and macro-organisms


    1. Introduction

   Outdoor fountains located in parks or urban environments are often constructed
using different lithotypes and are generally equipped with a water supply and deco-
rative elements made of metals or metal alloys [1-2]. Different biological systems,
mainly related to the presence of water, may colonize these artifacts. The photosyn-
thetic microflora, algae, cyanobacteria, lichens, mosses, vascular plants on stones,
represent a complex ecosystem that develops depending on environmental condi-
tions and the physical and chemical properties of the material. These initial popula-
tions can also promote the growth of other communities and can be involved in the




                                                                                                 CONSERVATION SCIENCE IN CULTURAL HERITAGE
biodeterioration of artifacts frequently enhanced by the indirect action of insects and
other animals [3-5]. Biological decay and the intensity of biodeterioration processes
are strongly influenced by water availability, and is determined by material-specific
parameters, such as porosity and permeability, environmental conditions of the site
and exposure of the object [6].
   Within the framework of co-operation between the University of Palermo and the
Salvare Palermo Foundation, the Fountain of the two Dragons in Palermo was identi-
fied as one of the monuments needing conservative restoration measures. In this sce-
nario, a monitoring campaign was undertaken in order to obtain preliminary results on
the conservation state and the biological systems colonizing the monument.
   The Fountain of the two Dragons was executed in 1630 by the sculptor Nunzio La
Mattina, according to the design of the architect Mariano Smiriglio [7]. The marble
fountain consists of one big basin (elliptical in shape) and two statues featuring drag-
ons, positioned on opposite sides; in the middle of the basin there is a large decorative
pinecone sculpture (Figure 1A).
   The two mythical sculptures are equipped with an appropriate water supply system
(Figure 1B) and surrounded by a small semicircular space.



*   Corresponding author: franco.palla@unipa.it

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Di Carlo, Lombardo, Barresi, Manachini, Palla, Corselli D’Ondes, Lo Giudice - BIOLOGICAL MACRO AND MICRO SYSTEMS




                                                                                                                        Figure 1. (A) View of the Fountain of the two Dragons; (B) detail of the water flow device in the
                                                                                                                        dragon statue on the left.



                                                                                                                           2. Evaluation of the state of conservation

                                                                                                                           The fountain is located in the old urban area of Palermo and a protective barrier
                                                                                                                        was erected to protect the space. Moreover, behind the fountain there are some trees
                                                                                                                        whose roots have caused the paving materials to break and come loose (Figure 2A);
                                                                                                                        the presence of planted trees increases leaves, fibers, pollen, flying insects, bird feces
                                                                                                                        on the monument (Figure 2D).




                                                                                                                        Figure 2. Deterioration signs. (A) Trees behind the fountain; (B) front of dragon with evidence
                                                                                                                        of water leaching, rusty patina; (C) other patinas and dirt on dragon’s wing; (D) vegetal remains
                                                                                                                        on dragon statues or plants inside fissures and loss of materials due to the presence of metal
                                                                                                                        brackets; (E) colored patinas on lower part of dragon; (F) flaking of material composing the rim
                                                                                                                        of fountain.


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    The conservation state of both basin and dragons is characterized by deterioration
processes. The basin is affected by discoloration phenomena, a widespread presence
of leaves or other plant remains, encrustations, flaking (Figure 2F), different pigmented
patinas and soiling. In addition, on the two statues there are several biodeteriogens
which include plants and mosses, insects, patinas, and alterations, such as discolora-
tion, rusty patinas, black crusts and dirty deposits, fissures, detachment of material.
Moreover, mechanical stress due to the presence of brackets made of metal and pipes
inside the structures is also evident (Figure 2C, E). Traces of past water leaching and
the consequent formation of biofilm and incrustations due to metal corrosion are distin-
guishable on the front of the dragons’ chests (Figure 2B).
    In order to define an adequate conservative restoration, the identification of both
macro and micro-biological deteriogens was performed through an integrated ap-
proach based on microscopy, in vitro culture, molecular biology investigation (PCR,
sequence analysis).

  3. Materials and methods

  3.1 Sampling

   In February 2014, biological sampling was performed on the fountain’s deco-
rative elements and basin surfaces. The biological samples were collected from
areas affected by chromatic alterations, deposits, exfoliations, incrustation, biologi-
cal or pigmented patinas. Sampling was performed by sterile swabs (Figure 3A,
B, C), by scalpel (Figure 3D, E, F) or by direct sampling of specimens by means
of tweezers.
   The sampling in proximity of the coloured patinas was justified by the fact that mi-
croorganisms contribute both to chemical-physical alteration of the constituent materi-
als and to the formation of pigmented patina on the surfaces. These micro-organisms




                                                                                                   CONSERVATION SCIENCE IN CULTURAL HERITAGE
are able to produce coloring pigments, such as chlorophyll, carotenoid, melanin, that
may generate chromatic variations towards a yellow, orange, red, or even brown col-
our [5]. Table 1 contains a description of the collected samples.

      Table 1. Samples collected with corresponding sampling area reported in Figure 3.
    Sample                          Sampling area                             Figure 3

 swab 11               base of pinecone             biological patina          A (star)

 swab 13              dragon on right side          pigmented area             B (star)

 swab 14               dragon on left side          pigmented area             C (star)

 sample 15                 basin edge                vegetal growth           D (circle)

 sample 7          dragon on left side (back)        vegetal growth           E (circle)

 sample 4          dragon on right side (wing)           larvae            F (green circle)

                                                        insects             F(grey circle)
 sample 5          dragon on right side (wing)
                                                      gastropods            F(blue circle)




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                                                                                                                        Figure 3. Sampling areas. (A-B-C) sampling on biological and pigmented patinas using sterile
                                                                                                                        swabs (stars); (D-E-F) sampling of macro biological systems by scalpel (colored circles).


                                                                                                                           3.2 Identification of microorganisms

                                                                                                                            Samples collected by swabs were diluted in liquid culture media. Solid nutritive
                                                                                                                        media (Nutrient Agar and Sabouraud, Difco) in Petri-plates were inoculated with 50 μl
                                                                                                                        of the resulting suspensions. The plates were incubated at 30°C for 16 up to 36 hours.
                                                                                                                        Isolated microorganisms were identified by morphological analysis and molecular biol-
                                                                                                                        ogy investigation. Microbial colony morphology was observed by stereomicroscope
                                                                                                                        (Wild Heerbrugg). The micro-morphology of the reproductive structures was identified
                                                                                                                        by identification keys [8], after staining with Lugol’s solution and optical microscope
                                                                                                                        (Leica) observation.
                                                                                                                            Molecular biology investigation was performed through ad hoc protocols, including
                                                                                                                        genomic DNA extraction by Genomic DNA Purification Kit (Fermentas) from isolated
                                                                                                                        colonies or directly from biological patinas (biofilm). Genomic DNA extracted from mi-
                                                                                                                        crobial colonies was utilized as a template for in vitro amplification (Polymerase Chain
                                                                                                                        Reaction) of target sequences [9-11]. Each PCR reaction mixture consisted of micro-
                                                                                                                        bial genomic DNA; 1X Reaction Buffer; 10 μM Forward primer; 10 μM Reverse primer;
                                                                                                                        2.5 mM dNTP mix; 5 mM MgCl2; 2Us of Taq DNA polymerase (Invitrogen). PCR prod-
                                                                                                                        ucts were analyzed by electrophoresis on 2% agarose gel in TAE (Tris-HCl/acetate/
                                                                                                                        EDTA) buffer, the sequencing was performed by Eurofins MWG-Operon, sequenc-


                                                                                                                   98
ing service (Germany) and sequence analysis by BLAST platform (NCBI-NIH–USA,
EMBL-Germany) [12, 13].

  3.3 Identification of macro-organisms

   Macro-systems collected in the different areas of the Fountain of the two Dragons
were observed by digital microscope (DinoLite) and stereomicroscope (Wild Heer-
brugg); bryophytes were characterized by optical microscope (Leica, 40X), after ap-
propriate preparation of the samples according to the taxa.

  4. Results

  4.1 Identification of microorganisms

   Analysis of samples 11, 14 and 15 revealed the presence of several bacterial and
fungal colonies. The morphological analysis of the bacteria grown on nutritive media
plates was carried out by direct microscopic observation, distinguishing pigmented
bacterial colonies (e.g., yellow, red, pinkish) (Figure 4). In particular, pigmented bac-
teria belonging to the Arthrobacter genera were identified by molecular investigations
(sample 11). Reddish and pinkish bacteria were identified as Arthrobacter spp. and
Paracoccus spp. (sample 13). In the same sample, fungal colonies belonging to Al-
ternaria spp. and Phoma spp. were revealed. Arthrobacter spp. and Paracoccus spp.
were also revealed in sample 14, as well as fungi Alternaria spp., Fusarium spp. and
Cladosporium spp. (Figure 5).




                                                                                                 CONSERVATION SCIENCE IN CULTURAL HERITAGE




                     Figure 4. Bacterial colonies grown on agar plates.




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                                                                                                                         Figure 5. Morphological analysis of fungi colonies. Alternaria (A) and Fusarium (C) isolated on
                                                                                                                         Sabouraud media and observed by optical microscope (40X), after staining with Lugol’s solution
                                                                                                                         (B-D).


                                                                                                                                                          Table 2. Microbial colonizers.

                                                                                                                          Samples (swab)                     Sampling areas                       Microorganisms

                                                                                                                                 11             base of pinecone           biological patina      Arthrobacter spp.

                                                                                                                                                                                                  Arthrobacter spp.
                                                                                                                                                                                                  Paracoccus spp.
                                                                                                                                 13           dragon on right side         pigmented area
                                                                                                                                                                                                   Alternaria spp.
                                                                                                                                                                                                     Phoma spp.

                                                                                                                                                                                                  Arthrobacter spp.
                                                                                                                                                                                                   Paracoccus spp.
                                                                                                                                 14            dragon on left side         pigmented area           Alternaria spp.
                                                                                                                                                                                                    Fusarium spp.
                                                                                                                                                                                                  Cladosporium spp.


                                                                                                                            Arthrobacter, Alternaria, Fusarium and Cladosporium represent the main mi-
                                                                                                                         crobial genera isolated from the fountain samples. These microorganisms are fre-
                                                                                                                         quently found on stone materials and outdoor monuments and may be considered
                                                                                                                         potential biodeteriogens, due to their metabolic products (e.g., organic acids, pig-
                                                                                                                         ments) [14].




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  4.2 Identification of macro-organisms

   Complex communities with the presence of plants and animals were observed in
some samples (Table 3). In sample 15 (from the basin edge for example), a Bryophyte
was revealed by stereo and optical microscopy observations (Figure 6).
   Aerial and sub-aerial parts were observed, seeds (Figure 7) of Stellaria media (weed
plant belonging to Caryophyllaceae) were recovered from the back of the left dragon.


                           Table 3. Vegetal and animal colonizers.
      Samples
                              Sampling areas                         Macroorganisms
  (scalpel, forceps)

     sample 15                   basin edge                      Bryophyte, Mosses

      sample 7           dragon on left side (back)       Stellaria media (Caryophyllaceae)

      sample 4          dragon on right side (wing)         Larvae (Diptera, Coleoptera)
                                                              Adult insects (Psocoptera,
      sample 5          dragon on right side (wing)
                                                                      Hemiptera)




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
Figure 6. Gametophyte sampled on basin edge. Stereomicroscope (A), optical microscope 10X
(B), and 40X (C) images.




     Figure 7. (A) Stellaria media (Caryophyllaceae); (B) Stereomicroscope 40X its seed.




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Di Carlo, Lombardo, Barresi, Manachini, Palla, Corselli D’Ondes, Lo Giudice - BIOLOGICAL MACRO AND MICRO SYSTEMS




                                                                                                                         Figure 8. (A) Dipteran pupae; (B) Coleoptera larva; (C) semiaquatic bugs Velia sp. (Heteroptera:
                                                                                                                         Gerromorpha); (D, E) terrestrial pulmonate (probably Aegopinella sp. and Leucostigma sp.).

                                                                                                                            A suitable environment and the presence of energy sources with organic and inor-
                                                                                                                         ganic nutrients contribute to biological colonization on exposed stone, favouring also
                                                                                                                         the settlement of different taxa of invertebrates (Figure 8A-E). Several pupae of my-
                                                                                                                         cophagous dipteran specimens were collected from the stone (Figure 8A). It was im-
                                                                                                                         possible to determine the species, as mycophagous flies can only be distinguished by
                                                                                                                         the morphological characteristics of adult males, and larval samples must be reared to
                                                                                                                         adulthood to obtain an adult male specimen. However, their presence is supported by
                                                                                                                         the growth of fungi, algae and lichens. An Arthropodes community was also represent-
                                                                                                                         ed by some coleopteran larvae (Figure 8B) and the semiaquatic bugs (Heteroptera:
                                                                                                                         Gerromorpha) belong to the genus Velia (Figure 8C). The latter actively forages and
                                                                                                                         sucks up prey, usually soft-bodied arthropods, collected from the surface of the dragon
                                                                                                                         on the right side. In addition to the indicated species in Figure 8 several individuals of
                                                                                                                         Psocopetera were also collected in the same areas.
                                                                                                                            The Molluscan community was represented by a terrestrial pulmonate gastropod:
                                                                                                                         the small land glass snail (probably Aegopinella nitidula of the family Oxychilidae, Fig-
                                                                                                                         ure 8D) and the door snail (Leucostigma sp. of the family Clausiliidae, Figure 8E);
                                                                                                                         these were observed on the stone supporting algal and lichenic growth.
                                                                                                                            These pulmonates are herbivorous, living on fresh and/or dead plant material. They
                                                                                                                         can also graze on algal films as they have specially modified spadelike radular teeth.
                                                                                                                         They also commonly feed on fungi.
                                                                                                                            All these animals contribute to the diffusion and propagation of new algae and fungi
                                                                                                                         colonies by means of their spores, soredia, algal cells and fecal pellets or by becom-
                                                                                                                         ing entrapped among their body parts (such as hairs). These taxa were recovered
                                                                                                                         in cracks or in hidden areas of the dragons and their activity, growth and swelling
                                                                                                                         can induce physical stress and mechanical breaks. Direct destructive action can be
                                                                                                                         both physical, caused mainly by grazing, and chemical, caused by the dropping of
                                                                                                                         excrements. Indirect damage results from organic substances accumulated on the
                                                                                                                         stone surfaces, which can serve as nutritive substrata for heterotrophic microorgan-
                                                                                                                         isms (bacteria and fungi).
                                                                                                                            The destroyers damage the constituents of the substrate while utilizing organic sub-
                                                                                                                         stances for their metabolic requirements. Insects, fungi and most bacteria are destroy-


                                                                                                                   102
ers. The consumers can be considered the least dangerous group in this field because
they feed on living matter from other micro and macro organisms. On the other hand,
they have a crucial role in controlling the growth of 2 other biodeteriogens, lichen-
eating snails and grazing animals.
    Despite the potential importance of invertebrates inhabiting our heritage and histori-
cal monuments, only scant literature is available [15] on the various aspects of biode-
terioration of stones due to invertebrates. Further study into the taxonomy, recruitment,
species richness, community, composition, ecological significance, biology, physiology
and reproduction of species that are potential biodeteriogens for historical monuments
is still needed.


      5. Conclusion

   The biological sampling on the decorative elements and basin surfaces was per-
formed on the Fountain of the two Dragons in Palermo. The samples were collected
from areas affected by chromatic alterations, deposits, exfoliations, incrustations, bio-
logical or pigmented patinas. Afterwards, characterization of plant residues and insects
was performed by microscopic investigations in order to reveal the main macro-biologi-
cal systems inhabiting the fountain. Cultivation-based techniques were then employed
in association with molecular analysis to give a complete overview of microbial taxa
able to colonize the surfaces of the artifacts.
   Pigmented bacteria belonging to Arthrobacter spp. and Paracoccus spp. were re-
vealed in collected samples that were characterized. In general, these bacteria de-
velop on stone artworks causing pigmentation and discoloration [16, 17].
   Fungi have a crucial role in the discoloration and mechanical degradation of stone in
cultural heritage; hyphae penetrate deeply into materials and can release extracellular
enzymes (enzymatic degradation and pigments production). Moreover, fungal spores




                                                                                                     CONSERVATION SCIENCE IN CULTURAL HERITAGE
are wind-dispersed and often extremely abundant in outdoor air. The main fungal colo-
nies revealed in the samples belong to Alternaria and Phoma genera. The mentioned
fungal genera are typically soil fungi that can induce mechanical exfoliation of stone
material by hyphae penetration or production of different pigments and organic acids
[18].


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  Biographical notes

   Enza Di Carlo graduated in “Biological Science” at the University of Palermo and
specialized in “Microbiology and Virology” at the School of Medicine at the same uni-
versity. She is a Research Fellow at the Laboratory of Biology and Biotechnology
for the Cultural Heritage (LABBBC) of the Department of Biological, Chemical and
Pharmaceutical Sciences and Technologies (STEBICEF) at the University of Palermo,
where she carries out microbiological monitoring of environments for the preservation
and use of Cultural Heritage.
   Giovanna Lombardo is a naturalist with a PhD in Plant Resources, from the Uni-
versity of Palermo and works at the Department of Biological, Chemical and Phar-
maceutical Sciences and Technologies (STEBICEF) of the same University. Dr. Lom-
bardo deals with in vitro cultures of plant tissues, plant conservation, genetic analysis
and molecular characterization of plant resources and also with ancient plant finds
(seeds and fruits) derived from archaeological excavations, including pollens. She is a
member of the Italian Botanical Society (SBI) and Italian Association of Archaeometry
(AIAr).
    Giovanna Barresi graduated in “Science for Conservation and Restoration” at the
University of Florence. She is a Research Fellow and works in the diagnostic-analytical
field and applied research for the enzymatic cleaning of artifacts of historical-artis-
tic interest at the Laboratory of Biology and Biotechnology for the Cultural Heritage
(LABBBC) of the Department of Biological, Chemical and Pharmaceutical Sciences
and Technologies (STEBICEF) at the University of Palermo.
    Barbara Manachini, PhD in Agricultural Entomology, Bologna University (Italy),
Master in Science of Nematology, Ghent University (Belgium), Master in scientific di-
dactics and divulgation, Roma Tre University (Italy), Degree in Natural Science, Milan




                                                                                                  CONSERVATION SCIENCE IN CULTURAL HERITAGE
University (Italy). Author and co-author of more than 150 published contributions. Co-
inventor of 2 patents. Senior researcher at the University of Milan (until 2007) and in
2012 obtained the award of National Scientific Qualification as Associate Professor in
Applied Entomology and Plant Pathology. She teaches entomology, at the University of
Palermo, in courses of Restoration and Conservation of Cultural Heritage, Natural Sci-
ence and Biology and Ecology of Plants. Evaluator for European Project (FP7 and Ho-
rizon 2020). Member of the Management Committee of the COST Action 862. Member
in the GMO panel of the European Food Safety Authority (EFSA) and ad hoc expert in
Plant Protection Products Non Target Organism and in-soil organisms working groups.
    Franco Palla is Associate Professor of Applied and Environmental Botany at the
University of Palermo, Italy. He is Professor and Coordinator of the Five-Year Degree
in Conservation and Restoration of Cultural Property (MRL02, certified professional
restorer). He is scientific head of the UNIPA Research Unit, for the Research Project
PON01_00625, It@cha (Italian Technology for Advanced Applications in Cultural Her-
itage). He was one of the members of the working groups in the cooperation project
Italy-Cambodia for Training Experts of Cultural Heritage, University of Palermo – Royal
University of Fine Arts and the Ministry of Culture and Fine Arts, Angkor, Cambodia. He
is Coordinator of the Laboratory of Biology and Biotechnologies for Cultural Heritage
at the Department of Biological, Chemical, and Pharmaceutical Science and Technolo-
gies (STEBICEF) of the University of Palermo.


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                                                                                                                            Gaetano Corselli D’Ondes, Architect; for more than thirty years he has worked in
                                                                                                                         the field of architectural restoration, in particular stone materials, frescoes, stuccoes,
                                                                                                                         mosaic coatings and iron ores. He served at the Superintendency BB.CC.AA. of Pal-
                                                                                                                         ermo between 1993 and 2003 by participating, among other works, in the restoration of
                                                                                                                         Maredolce Castle and took care of the underground architecture of Palermo. Currently,
Di Carlo, Lombardo, Barresi, Manachini, Palla, Corselli D’Ondes, Lo Giudice - BIOLOGICAL MACRO AND MICRO SYSTEMS




                                                                                                                         he provides consulting services in the field of restoration at Mediterranean Engineer-
                                                                                                                         ing on behalf of which he also directed the work of the Martorana church in Palermo.
                                                                                                                             Silvana Lo Giudice, Architect in Palermo, she is specialized in “Conservation of
                                                                                                                         Historical Architecture”. From 1993 she has been a member of the Salvare Palermo
                                                                                                                         Association, Cultural and Scientific Disclosure Commission and Advisor of the Board of
                                                                                                                         Directors of the New Salvare Palermo Foundation. From 2010 she has been a member
                                                                                                                         of the editorial office of Per; she is a member of the Restoration Committee in the role
                                                                                                                         of coordinator of restoration intervention in Palermo and permanent art exhibitions.
                                                                                                                         She is author of several publications (Le radici della Fotogrammetria a Palermo, 1992;
                                                                                                                         L’impiego dei fotogrammi del volo Italia (1989) e dell’ortofotocarta, da essi derivata,
                                                                                                                         per l’aggiornamento delle tavolette 1:25.000 relative al territorio comunale di Palermo,
                                                                                                                         1993; I risultati della tesi di laurea nel volume Il territorio: questo sconosciuto, 1997; Il
                                                                                                                         CD multimediale “al di là del mare”, Comune di Gioiosa Marea, 2001; Disegni in luce,
                                                                                                                         Comune di Palermo, 2002; in Palermo Normanna. Proposte di itinerari didattici, As-
                                                                                                                         sessorato regionale BB.CC.AA. e P.I. – Soprintendenza BB.CC.AA. di Palermo, 2003;
                                                                                                                         La chiesa Holy Cross a Palermo, 2008); since 2008 she has been Dirigente Tecnico
                                                                                                                         Architetto del ruolo tecnico dei Beni Culturali.




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   Summary
   Stone works of art located outdoors are exposed to natural deterioration, due to
several physical, chemical and biological factors. Biological macro- and micro-systems
(e.g. weeds, insects, algae, mosses, fungi and bacteria) may induce the biodeteriora-
tion of stone materials. In February 2014, the state of conservation of the Fountain of
the two Dragons in Palermo was examined, during which time biological colonization in
some areas of the fountain and statues, was also detected. The monument represents
an excellent substrate for the development and growth of microrganisms and organ-
isms that need a continuous supply of water. Direct solar irradiance promotes the de-
velopment of photoautotrophic organisms, bryophyte flora, in addition to several micro-
bial genera, responsible for pigmentation, discoloring, efflorescence. After autotrophic
colonization, some organisms find an ideal habitat also during wintertime, including
two species of gastropods and two species of Hemiptera, omnivorous, a species of
Collembola, mostly fungivorous. This interdisciplinary study has enabled the detection
and identification of different biological communities, providing information for a subse-
quent project of preventive conservation of the fountain and its surroundings.


    Riassunto
    I manufatti lapidei esposti all’aperto sono sottoposti a processi naturali di deterio-
ramento, dovuti a fattori di natura fisica, chimica e biologica. I macro e micro sistemi
biologici (per esempio semi, insetti, alghe, muschi, funghi e batteri) possono causare
il deterioramento dei materiali lapidei. Nel Febbraio del 2014 è stato effettuato uno
studio sullo stato di conservazione della Fontana dei due Draghi, Palermo, durante
il quale sono state individuate diverse aree interessate da colonizzazione biologica,
sia all’interno della fontana e sia sulle statue decorative. Il monumento rappresenta
un substrato di crescita eccellente per lo sviluppo di microorganismi e di organismi
che necessitano di un continuo supporto di acqua. Inoltre, l’irradiamento solare diretto




                                                                                                   CONSERVATION SCIENCE IN CULTURAL HERITAGE
promuove lo sviluppo di organismi autotrofi, briofite oltre a diversi generi microbici re-
sponsabili dei fenomeni di pigmentazione, alterazioni cromatiche, efflorescenze. Dopo
la colonizzazione autotrofica, molti organismi trovano l’habitat ideale anche durante il
periodo invernale, incluse due specie di gastropodi e due specie di Hemiptera, onnivo-
ri, una specie di Collembola, principalmente fungivoro. Questo studio interdisciplinare
ha permesso di identificare differenti comunità biologiche, fornendo informazioni utili
per un futuro progetto di conservazione preventiva della fontana e il suo ambiente
circostante.




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