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| Titel |
Bioerosion by euendoliths decreases in phosphate-enriched skeletons of living corals |
| VerfasserIn |
C. Godinot, A. Tribollet, R. Grover, C. Ferrier-Pagès |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 7 ; Nr. 9, no. 7 (2012-07-02), S.2377-2384 |
| Datensatznummer |
250007173
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| Publikation (Nr.) |
 copernicus.org/bg-9-2377-2012.pdf |
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| Zusammenfassung |
| While the role of microboring organisms, or euendoliths, is relatively well
known in dead coral skeletons, their function in live corals remains poorly
understood. They are suggested to behave like ectosymbionts or parasites,
impacting their host's health. However, the species composition of microboring
communities, their abundance and dynamics in live corals under various
environmental conditions have never been explored. Here, the effect of
phosphate enrichment on boring microorganisms in live corals was tested for
the first time. Stylophora pistillata nubbins were exposed to 3 different treatments (phosphate
concentrations of 0, 0.5 and 2.5 μmol l−1) during 15 weeks. After
15 weeks of phosphate enrichment, petrographic thin sections were prepared
for observation with light microscopy, and additional samples were examined
with scanning electron microscopy (SEM). Euendoliths comprised mainly
phototrophic Ostreobium sp. filaments. Rare filaments of heterotrophic fungi were also
observed. Filaments were densely distributed in the central part of nubbins,
and less abundant towards the apex. Unexpectedly, there was a visible
reduction of filament abundance in the most recently calcified apical part
of phosphate-enriched nubbins. The overall abundance of euendoliths
significantly decreased, from 9.12 ± 1.09% of the skeletal surface
area in unenriched corals, to 5.81 ± 0.77% and 5.27 ± 0.34% in 0.5 and 2.5 μmol l−1-phosphate enriched corals
respectively. SEM observations confirmed this decrease. Recent studies have
shown that phosphate enrichment increases coral skeletal growth and
metabolic rates, while it decreases skeletal density and resilience to
mechanical stress. We thus hypothesize that increased skeletal growth in the
presence of phosphate enrichment occurred too fast for an effective
expansion of euendolith growth. They could not keep up with coral growth, so
they became diluted in the apex areas as nubbins grew with phosphate
enrichment. Results from the present study suggest that coral skeletons of
S. pistillata will not be further weakened by euendoliths under
phosphate enrichment. |
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