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| Titel |
The influence of light attenuation on the biogeomorphology of a marine karst cave, the Puerto Princesa Underground River, Palawan, the Philippines. |
| VerfasserIn |
Martin Coombes, Emanuela Claudia La Marca, Jo De Waele, Leonardo Piccini, Larissa Naylor, Francesco Sauro |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093554
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| Publikation (Nr.) |
 EGU/EGU2014-8393.pdf |
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| Zusammenfassung |
| Karst caves are unique biogeomorphological systems. Cave walls offer novel habitat for
microorganisms which in-turn have a geomorphological role via their involvement in rock
weathering, erosion and mineralisation. The attenuation of light with distance into caves is
known to affect ecology, but the implications of this for biogeomorphological processes and
forms have seldom been examined. Here we describe a semi-quantitative microscopy study
comparing the extent, structure, thickness and penetration depth of biocover for the Puerto
Princesa Underground River system in Palawan, the Philippines. This extensive marine
karst cave is composed of a main active river branch, ending directly in the sea and
influenced by tidal movements up to 4 km distance from the coastline, and several fossil
branches. It is a unique habitat for a multitude of cave-adapted fauna, and a natural
UNESCO World Heritage Site chosen as one of the Seven Wonders of Nature in
2012.
Organic growth at the entrance of the cave was abundant (100% occurrence) and
complex, dominated by phototrophic organisms (green microalgae, diatoms, cyanobacteria,
mosses, actinobacteria, and lichens). Thickness of this layer was 0.28 ± 0.18 mm with active
endolith penetration into the limestone (mean depth = 0.13 ± 0.03 mm). In contrast,
phototrophs were rare 50 m into the cave and biofilm cover was very thin (0.01 ± 0.01 mm)
and spatially patchy (33% occurrence). Endolithic growth here was also thin (< 0.01 mm)
and non-uniform. No biocover was observed 250 m from the entrance. In addition to organic
influences, micromorphologies of possible chemical origin were observed at all distances into
the cave.
We attribute these differences to light-induced stress gradients, showing that light
influences phototroph abundance that in turn has associated consequences for bioweathering
and bioerosion in caves. This may also reflect the relative contributions of organic and
inorganic processes in the development of distinct morphological features such as notches,
for which variability in formation rates between locations is currently poorly understood. |
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