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Deep‐sea coral δ 13 C: A tool to reconstruct the difference between seawater pH and δ 11 B‐derived calcifying fluid pH
Author(s) -
Martin Patrick,
Goodkin Nathalie F.,
Stewart Joseph A.,
Foster Gavin L.,
Sikes Elisabeth L.,
White Helen K.,
Hennige Sebastian,
Roberts J. Murray
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066494
Subject(s) - seawater , coral , ocean acidification , deep sea , isotopes of boron , artificial seawater , geology , mineralogy , oceanography , chemistry , boron , environmental chemistry , analytical chemistry (journal) , organic chemistry
The boron isotopic composition ( δ 11 B) of coral skeleton is a proxy for seawater pH. However, δ 11 B‐based pH estimates must account for the pH difference between seawater and the coral calcifying fluid, ΔpH. We report that skeletal δ 11 B and ΔpH are related to the skeletal carbon isotopic composition ( δ 13 C) in four genera of deep‐sea corals collected across a natural pH range of 7.89–8.09, with ΔpH related to δ 13 C by ΔpH = 0.029 × δ 13 C + 0.929, r 2 = 0.717. Seawater pH can be reconstructed by determining ΔpH from δ 13 C and subtracting it from the δ 11 B‐derived calcifying fluid pH. The uncertainty for reconstructions is ±0.12 pH units (2 standard deviations) if estimated from regression prediction intervals or between ±0.04 and ±0.06 pH units if estimated from confidence intervals. Our new approach quantifies and corrects for vital effects, offering improved accuracy relative to an existing δ 11 B versus seawater pH calibration with deep‐sea scleractinian corals.