Microstructural evolution and nanoscale crystallography in scleractinian coral spherulites

van de Locht, Renée, Verch, Andreas, Saunders, Martin, Dissard, Delphine, Rixen, Tim, Moya, Aurélie, and Kröger, Roland (2013) Microstructural evolution and nanoscale crystallography in scleractinian coral spherulites. Journal of Structural Biology, 183 (1). pp. 57-65.

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Abstract

One of the most important aspects in the research on reef-building corals is the process by which corals accrete biogenic calcium carbonate. This process leads to the formation of a mineral/organic composite and it is believed that the development of the nano- and microstructure of the mineral phase is highly sensitive to the growth conditions.

Transmission electron microscopy (TEM) analysis of large-scale (10 × 30 μm) focused ion beam (FIB) prepared lamellae was performed on adult and juvenile scleractinian coral skeleton specimens. This allowed for the investigation of the nano and microstructure and the crystallographic orientation of the aragonite mineral. We found the following microstructural evolution in the adult Porites lobata specimens: randomly oriented nanocrystals with high porosity, partly aligned nanocrystals with high porosity and areas of dense acicular crystals of several micrometers extension, the latter two areas are aligned close to the [0 0 1] direction (Pmcn space group). To the best of our knowledge, for the first time the observed microstructure could be directly correlated with the dark/bright bands characteristic of the diurnal growth cycle. We hypothesize that this mineral structure sequence and alignment in the adult specimen is linked to the photosynthetic diurnal cycle of the zooxanthellea regulating the oxygen levels and organic molecule transport to the calcifying medium. These observations reveal a strong control of crystal morphology by the organism and the correlation of the accretion process.

No indication for a self-assembly of nanocrystalline units, i.e., a mesocrystal structure, on the micrometer scale could be found.

Item ID: 29061
Item Type: Article (Research - C1)
ISSN: 1095-8657
Keywords: biomineralization, transmission electron microscopy, aragonite, crystallography
Funders: Engineering and Physical Sciences Research Council (EPSRC), University of York, GBR, Australian Research Council (ARC), ARC Centre of Excellence for Coral Reef Studies, James Cook University (JCU)
Projects and Grants: EPSRC grant no. EP/I001514/1, ARC grant DP0986505
Date Deposited: 28 Aug 2013 05:31
FoR Codes: 06 BIOLOGICAL SCIENCES > 0608 Zoology > 060807 Animal Structure and Function @ 50%
06 BIOLOGICAL SCIENCES > 0608 Zoology > 060808 Invertebrate Biology @ 30%
06 BIOLOGICAL SCIENCES > 0608 Zoology > 060803 Animal Developmental and Reproductive Biology @ 20%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 70%
96 ENVIRONMENT > 9603 Climate and Climate Change > 960305 Ecosystem Adaptation to Climate Change @ 30%
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