title: Biotic control of skeletal growth by scleractinian corals in aragonite-calcite seas.
abstract: Modern scleractinian coral skeletons are commonly composed of aragonite, the orthorhombic form of CaCO3. Under certain conditions, modern corals produce calcite as a secondary precipitate to fill pore space. However, coral construction of primary skeletons from calcite has yet to be demonstrated. We report a calcitic primary skeleton produced by the modern scleractinian coral Acropora tenuis. When uncalcified juveniles were incubated from the larval stage in seawater with low mMg/Ca levels, the juveniles constructed calcitic crystals in parts of the primary skeleton such as the septa; the deposits were observable under Raman microscopy. Using scanning electron microscopy, we observed different crystal morphologies of aragonite and calcite in a single juvenile skeleton. Quantitative analysis using X-ray diffraction showed that the majority of the skeleton was composed of aragonite even though we had exposed the juveniles to manipulated seawater before their initial crystal nucleation and growth processes. Our results indicate that the modern scleractinian coral Acropora mainly produces aragonite skeletons in both aragonite and calcite seas, but also has the ability to use calcite for part of its skeletal growth when incubated in calcite seas.
authors.affiliation: Graduate School of Science and Technology, Shizuoka University, Suruga-ku, Shizuoka, Japan.
authors.forename: Tomihiko
authors.initials: T
authors.lastname: Higuchi
authors.affiliation: Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Fujimura
authors.affiliation: Graduate School of Science and Technology, Shizuoka University, Suruga-ku, Shizuoka, Japan.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Yuyama
authors.affiliation: Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Motobu, Okinawa, Japan.
authors.forename: Saki
authors.initials: S
authors.lastname: Harii
authors.affiliation: Shimoda Marine Research Center, University of Tsukuba, Shimoda, Shizuoka, Japan.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Agostini
authors.affiliation: Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan.
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Oomori
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism*; D002119:Calcium Carbonate / Q000378:metabolism*; D002413:Cations, Divalent; D007814:Larva / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D008274:Magnesium / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D012623:Seawater / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D002413:Cations, Divalent; D002119:Calcium Carbonate; D008274:Magnesium; D002118:Calcium