LICHENS ON ROAD BRIDGES LOCATED IN URBAN, RURAL AND COASTAL ENVIRONMENTS OF BUENOS AIRES PROVINCE, ARGENTINA

Transcription

1 LICHENS ON ROAD BRIDGES LOCATED IN URBAN, RURAL AND COASTAL ENVIRONMENTS OF BUENOS AIRES PROVINCE, ARGENTINA Vilma G. Rosato, L.P. Traversa. LEMIT (Laboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológica). La Plata, Argentina. Instituto Spegazzini Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata La Plata, Argentina Abstract Lichens were found growing on road bridges from different environments of Buenos Aires Province, Argentina. The aim of this paper is to identify them, and assess the damage they may produce. Lichens were collected by scraping them, observed under stereomicroscope and optical microscope and identified with keys. The bridges sampled are placed in different environments: urban, rural and coastal (La Plata River coast and the Atlantic coast). The most abundant and widespread were citrina, albescens and Lecania erysibe. Other species were found only in the coastal zone or in the central zone. It was noted that the diversity of materials allows a greater diversity of lichens,. On the contrary, Palazzo Bridge in La Plata only had algae growing on it, probably because it is in a shaded place under the trees. Gerardi Bridge (Gonnet, La Plata District) has also a poor lichen flora. This is attributed to the pollution caused by the dense traffic. The presence of lichens, particularly C. citrina and L. albescens is a problem for the appearance of the bridges. These species damage the surface of the substrate by mechanical penetration of hyphae (fungal filaments) into the substratum and the production of oxalic acid. Introduction. Road bridges, like any other engineering building, are exposed to different deterioration agents, including biological ones such as lichens. These organisms result from the symbiosis of a fungus (mycobiont) and an alga (phycobiont). The presence of the alga allows it to photosynthetize in presence of light, turning water and carbon dioxide into carbohydrates. 1

2 Lichens are organisms able to tolerate extreme temperatures and drying that usually grow on barks and rocks of different kinds, which can also colonize man-made substrata such as glasses, metals, tiles, bricks, etc. Just like other microorganisms such as fungi and bacteria, they can deteriorate these materials, and there is a wide literature on the subject. Because of its extension, Buenos Aires Province has variety of environments, and the road bridges are placed in different situations: urban, rural, riverside environments, sea coast and hills, so the carried out surveys had the aim to identify the present species and to analyze the possible influence of environment factors on the distribution. Materials and methods Lichens were obtained by scraping them off the substratum and were observed with a Willd M-5 stereomicroscope. Hand sections and squash preparations were mounted in water and then observed with a Willd M-20 optical microscope. Thallus, asci and ascospores were measured and the usual histochemical reactions (K, potassium hydroxide; C, sodium hypochlorite; KC, a combination of the former two, and Pd, paraphenilendiamine). These data were used to identify them with keys [1], [2], [3], [4]. Observed Bridges. Bridge over El Gualicho stream (Rauch district) -Rural environment (Table 4) Sierras Bayas bridge (Olavarría district)- Rural enviroment (Photo 3) (Table 4) Urban bridges over Azul stream (Olavarría district)- urban environment (Photo 4) Bridges of Province Road Nº 11. Section 1. From La Plata to the junction with Road 36 (Rio de La Plata coast) (Table 1) Section 2: From Channel 15 to General Lavalle District (Atlantic Coast) (Table 2) Bridge of Province Road Nº 215 (Lobos district). Rural environment (Table 4) La Postrera bridge (Lezama, Chascomús district) Cost of La Plata River (Table 3) Palazzo bridge (El Bosque Park, La Plata) Gerardi Bridge (Road 1- General Belgrano Road. Gonnet, La Plata district) Urban-industrial environment, dense traffic road. (Photo1) Results The lichen species found are listed in the tables corresponding to each structure (Table 1, Table 2, Table 3 and Table 4). As it can be seen from the tables, citrina is a common and widespread species that was found in almost all of the inspected bridges, as well as albescens. Other species are found in certain localities: for instance, anthoria parietina grows only on the bridges near the sea coast, or Staurothele frustulenta that grows on in rural habitats in the center of the Province. On Palazzo bridge no lichens were found. The bridge is colonized by green algae (chlorophytes) that grow over the mortar. They are also on the rock breakwater, but on the cement joints and not on the granite rock. On the cement joints of the breakwaters some colonies of mosses (bryophytes) were also found. As regards Gerardi-bridge (Photo 1), only Lecania erysibe was found, along with very scarce citrina. The last is a very common and widespread species, with the ability to penetrate the substrate up to 1-1,5 mm by the mechanical action of the hyphae as observed with thin 2

3 sections and SEM photomicrographs. It also produces a chemical deterioration through the action of oxalic acid, analyzed by IRS (Infra Red Spectroscopy)[5]. This acid combines with the hydrated calcium compounds causing a loss of Ca from 60% to only 8%, which was measured with EDA microanalysis. As a result of the combined effect of these mechanisms, there is a damage that is only superficial, but affects the esthetics of the bridges. Other common lichens such as albescens and Staurothele frustulenta have also a similar action. Photo 1 Gerardi Bridge 3

4 Table 1- Species found on road 11 up to the junction with road 36 (Photo 2) Species Locality citrina holocarpa El Pescado Stream (rural environment) Zapata Stream (rural Cañada Arregui (rural Buriñigo Stream (rural Atalaya (river coast Juan Blanco Stream (river coast Concrete Wood Concrete Concrete Concrete Concrete Wood Concrete - scarce very scarce Lecania sp. albescens chlarotera Pertusaria sp. erythrantha Photo 2 Bridge across Zapata stream. 4

5 Table 2- Bridges of road 11 from the junction with road 36 to Gral. Lavalle District. (Seacoast environment) PLACE Canal El Porteño RÍO SALADO Substratum Cement Rock Cement - (quarzite?) plaster SPECIES citrina dispersa holocarpa Lecania aff. erysibe anthoria parietina Candelaria concolor Hyperphyscia coralloides Canal 15 (Bridge) Cement Paint of the metal floodgate TABLE 3- Species found on La Postrera bridge, indicating the material they colonize [6]. (River-coast environment). SPECIES anthoparmelia conspersa americana Staurothele monosporoides Punctelia microsticta Hypotrachyna sp Ramalina celastri MATERIAL Granite Cement Painted metal Teloschistes chrysophthalmus citrina Lecania erysibe 5

6 Table 4- Lichens from the center of Buenos Aires Province. (Photos 3-4) Locality Material Species Olavarría Rural environment Sierras Bayas Black Lime stone Urban environment Rauch (El Gualicho stream) Lobos Hornos St. Necochea St. Rural env. Rural env. Cement Cement Cement Cement citrina holocarpa albescens Lecania erysibe Heterodermia Speciosa Staurothele frustulenta Photo 3 Photo 4 Bridge of Sierras Bayas Urban bridge of Olavarría Final conclusions. - The most widespread and abundant species are: citrina, albescens and Lecania erysibe. - Some lichen species appear in special environments. For instance, on the bridges of Province road 11, anthoria parietina, a cosmopolitan species able to colonize different substrata, was 6

7 found only by Channel 15 and the bridges near the sea coast. In this case, it was found on the cement and the paint of the metal floodgate. It is also worthy to mention that Hyperphyscia coralloides was found on the painting of the metal floodgate. It is confirmed that this species, commonly fond on tree barks, can colonize the painted metal, as it was observed in Tandil. - As regards the rural environments in the central region of the Province, there is a predominance of L. erysibe (Bridge over El Gualicho Stream, Rauch district; Bridge of Sierras Bayas, Olavarría district), and the presence of Heterodermia speciosa (Sierras Bayas, Olavarría district). - The diversity of materials enhances the diversity of species, as there are species associated to certain substrata. This was clearly observed in La Postrera Bridge (Lezama, Chascomús district), as already observed in a previous paper (Rosato, 2003). On the bridges of road 11 up to the road 36 only citrina, C. holocarpa and albescens appear on the cement, and the difference is evident with the species present on the wooden bridge, where chlarotera, Pertusaria sp., erythrantha and anthoria parietina were found. - On Palazzo Bridge only algae and mosses appear. The absence of lichens is due most probably to the shadow of trees, whereas algae benefit from that situation. It must also be mentioned that algae and mosses do not colonize granitic rock but prefer cementiceous materials, which indicates they develop better in a moderately basic ph. - On Gerardi Bridge, placed on General Belgrano road at the locality of Gonnet (La Plata district) there is Lecania erysibe and scarce C. citrina. This is attributed to the pollution caused by the high density of traffic. -Although lichens, particularly C. citrina, penetrate the substrate, the damage they cause is superficial and mostly of an esthetical nature. Literature [1] Adler, M.T., Clave de los géneros y las especies de Parmeliaceae (Lichenes, Ascomycotina) de la Provincia de Buenos Aires (Argentina), Bol. Soc. Argentina de Botánica 28 (1-2) [2] Ozenda, P. and Clauzade, G.,1970- Les Lichens. Étude biologique et flore illustreé. (Masson et. Cie.Paris.). [3] Poelt, J., Bestimmungschlüssel der europäischer Flechten. (Cramer, Lehre.) [4] Scutari, N.C Estudios sobre Pyxinaceae foliosas (les, Ascomycotina) de la Argentina IV: Clave de los géneros y las especies de la Provincia de Buenos Aires, Boletín Sociedad Argentina de Botánica 28 (1-2) (1992) [5] Traversa, L.P., Iasi, R., Zicarelli, S. y Rosato, V. G., Biodeterioro de morteros y hormigones por acción de los líquenes. Hormigón 35: [6] Rosato, V. G., Lichens found on La Postrera Bridge across Salado River, Chascomús (Buenos Aires Province). IN: Microbial Impact on Building Materials. Proceedings of the International RILEM Conference, 8-9 September 2003, Lisbon, Portugal. (M. Ribas Silva, Ed.):