The role of symbiotic algae in the formation of the coral polyp skeleton: 3-D morphological study based on X-ray microcomputed tomography

Shinya Iwasaki, Mayuri Inoue, Atsushi Suzuki, Osamu Sasaki, Harumasa Kano, Akira Iguchi, Kazuhiko Sakai, Hodaka Kawahata

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Symbiotic algae of primary polyps play an important role in calcification of coral skeletons. However, the function of the symbiotic algae, including the way they influence the physical features of their host skeleton under various conditions, is not well understood. We used X-ray microcomputed tomography to observe skeletal shape characteristics in symbiotic and aposymbiotic primary polyps of Acropora digitifera that were cultured at various temperature and pCO2 levels (temperature 27, 29, 33°C; pCO2 400, 800, 1000 µatm). Symbiotic polyps had a basal plate with a well-developed folding margin supporting the branched skeleton, whereas aposymbiotic ones did not. The features of the folding margin suggest that it might be the initial growth stage of the epitheca. In addition, three-dimensional (3-D) morphological measurements made by X-ray microcomputed tomography show that the branched skeletons of symbiotic primary polyps were taller than those of aposymbiotic ones, suggesting that zooxanthellae in coral primary polyps play a critical role in the height growth of skeletal branches. Furthermore, results of the temperature- and pCO2-controlled experiments suggest that global warming might greatly affect the activity of zooxanthellae, whereas ocean acidification might reduce calcification by damaging the coral host itself. Our findings provide new knowledge about the role of zooxanthellae in coral calcification.

Original languageEnglish
Pages (from-to)3629-3637
Number of pages9
JournalGeochemistry, Geophysics, Geosystems
Volume17
Issue number9
DOIs
Publication statusPublished - Sep 1 2016

Keywords

  • X-ray micro-CT
  • basal plate
  • coral
  • skeletal shape
  • skeletal weight
  • symbiosis

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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