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Seasonal variations in the boron isotopic composition of coral: A productivity signal?
Author(s) -
Hemming N. G.,
Guilderson T. P.,
Fairbanks R. G.
Publication year - 1998
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/98gb02337
Subject(s) - coral , isotopes of boron , boron , isotopes of carbon , isotope , carbon fibers , δ13c , stable isotope ratio , environmental chemistry , productivity , isotope analysis , environmental science , oceanography , chemistry , geology , total organic carbon , materials science , composite material , macroeconomics , physics , organic chemistry , quantum mechanics , composite number , economics
Micro‐analysis of a western equatorial Pacific coral across two annual cycles reveals seasonal variation in the boron isotope composition. A heavy boron isotope spike is found coincident with a heavy carbon isotope spike in samples collected from the high density bands in the coral head. The heavy isotope values in both carbon and boron are consistent with high productivity of coral symbionts during periods of high insolation. During these high productivity periods, the symbionts fix carbon and thus produce a residual heavy carbon pool and CO 2 depletion. Calcification from the resulting high p H pool results in heavier boron isotope compositions in the coral as the isotopic composition of the aqueous boron species that is incorporated in the coral skeleton (BOH 4 − ) increases with p H. This study suggests that coupled carbon and boron isotope studies may lead to a better understanding of coral calcification processes and a more lucid understanding of coral δ 13 C records.