Open AccessThe role of symbiotic algae in the formation of the coral polyp skeleton: 3‐ D morphological study based on X ‐ray microcomputed tomography
Author(s) -
Iwasaki Shinya,
Inoue Mayuri,
Suzuki Atsushi,
Sasaki Osamu,
Kano Harumasa,
Iguchi Akira,
Sakai Kazuhiko,
Kawahata Hodaka
Publication year - 2016
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2016gc006536
Subject(s) - zooxanthellae , coral , algae , skeleton (computer programming) , calcification , biology , symbiosis , botany , anatomy , ecology , paleontology , pathology , medicine , bacteria
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 p CO 2 levels (temperature 27, 29, 33°C; p CO 2 400, 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 p CO 2 ‐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.