Assessing scleractinian corals as recorders for paleo-pH: Empirical calibration and vital effects

LDEO Publication: 
Publication Type  Journal Article
Year of Publication  2004
Authors  Hoenisch, B.; Hemming, N. G.; Grottoli, A. G.; Amat, A.; Hanson, G. N.; Buma, J.
Journal Title  Geochimica Et Cosmochimica Acta
Volume  68
Issue  18
Pages  3675-3685
Journal Date  Sep
ISBN Number  0016-7037
Accession Number  ISI:000223632900005
LDEO Publication Number  6647
Key Words  boron isotopic composition; sea co2 exchange; globigerinoides-sacculifer; ice core; community metabolism; skeletal delta-c-13; carbonate chemistry; stable-isotopes; atmospheric co2; ocean ph

Laboratory experiments on the branching, symbiont-bearing coral genus Porites and Acropora have been carried out to determine the dependence of the skeletal boron isotopic composition (sigma(11)B) on the pH of seawater. The results show a clear relationship similar to previously established empirical calibrations for planktonic foraminifera and inorganic calcite. A -0.6parts per thousand offset exists between P. cylindrica and A. nobilis which is systematic over the pH range of 7.7-8.2. To test whether the VB of coral skeletons changes with physiological processes such as photosynthesis and respiration, corals were grown along a depth transect in their natural environment and under controlled conditions in the laboratory at varying light intensities and food supply. Although we also observe an isotopic offset between P. compressa and Montipora verrucosa, neither experimental treatment systematically changed the sigma(11)B of the two species. These findings are encouraging for using the boron isotope paleo-pH proxy in corals, because it appears that seawater pH is the dominant control on the boron isotopic composition in corals. Copyright (C) 2004 Elsevier Ltd.


850SOTimes Cited:13Cited References Count:55

URL  <Go to ISI>://000223632900005
DOI  DOI 10.1016/j.gca.2004.03.0026