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Title: Amorphous calcium carbonate particles form coral skeletons

Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO 3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived pastmore » CO 2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya.« less
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [4] ;  [4] ;  [4] ; ORCiD logo [2]
  1. Univ. of Haifa, Haifa (Israel)
  2. Univ. of Wisconsin-Madison, Madison, WI (United States)
  3. Univ. of Haifa, Haifa (Israel); The Interuniversity Institute of Marine Science, Eilat (Israel)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; FG02-07ER15899; BSF-2010065; BSF-2014035
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 37; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 58 GEOSCIENCES; mesocrystal; PEEM; calcification crisis; vital effects; ocean acidification
OSTI Identifier:
1377090
Alternate Identifier(s):
OSTI ID: 1408474