Colonization and weathering of engineering materials by marine microorganisms: an SEM study |
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| Authors: | M A Coombes L A Naylor R C Thompson L Gómez‐Pujol R J Fairhurst |
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| Institution: | 1. Geography, College of Life and Environmental Sciences, University of Exeter in Cornwall, Tremough Campus, Penryn, Cornwall, TR10 9EZ, UK;2. Marine Biology and Ecology Research Centre, University of Plymouth, Drake Circus, Plymouth, Devon, PL4 8AA, UK;3. Mediterranean Institute for Advanced Studies, IMEDEA (CSIC‐UIB), Miquel Marquès 21, E07190 Esporles, Balearic Islands, Spain;4. Departament de Ciències de la Terra, Universitat de les Illes Balears, Cra. Valldemossa km 7.5, E07122 Palma, Balearic Islands, Spain;5. Camborne School of Mines, College of Engineering, Mathematics and Physical Sciences, University of Exeter in Cornwall, Tremough Campus, Penryn, Cornwall, TR10 9EZ, UK |
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| Abstract: | Microorganisms are a ubiquitous feature of most hard substrata on Earth and their role in the geomorphological alteration of rock and stone is widely recognized. The role of microorganisms in the modification of engineering materials introduced into the intertidal zone through the construction of hard coastal defences is less well understood. Here we use scanning electron microscopy (SEM) to examine microbial colonization and micro‐scale geomorphological features on experimental blocks of limestone, granite and marine concrete after eight months' exposure in the intertidal zone in Cornwall, UK. Significant differences in the occurrence of microbial growth features, and micro‐scale weathering and erosion features were observed between material types (ANOVA p < 0·000). Exposed limestone blocks were characterized by euendolithic borehole erosion (99% occurrence) within the upper 34·0 ± 12·3 µm of the surface. Beneath the zone of boring, inorganic weathering (chemical dissolution and salt action) had occurred to a depth of 125·0 ± 39·0 µm. Boring at the surface of concrete was less common (27% occurrence), while bio‐chemical crusting was abundant (94% occurrence, mean thickness 45·1 ± 27·7 µm). Crusts consisted of biological cells, salts and other chemical precipitates. Evidence of cryptoendolithic growth was also observed in limestone and concrete, beneath the upper zone of weathering. On granite, biological activity was restricted to thin epilithic films (<10 µm thickness) with some limited evidence of mechanical breakdown. Results presented here demonstrate the influence of substratum lithology, hardness and texture on the nature of early micro‐scale colonization, and the susceptibility of different engineering materials to organic weathering and erosion processes in the intertidal zone. The implications of differences in initial biogeomorphic responses of materials for long‐term rock weathering, ecology and engineering durability are discussed. Copyright © 2010 John Wiley & Sons, Ltd. |
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| Keywords: | biological weathering biogeomorphology SEM coastal engineering biofilm |
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