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Coral skeleton P/Ca proxy for seawater phosphate: Multi-colony calibration with a contemporaneous seawater phosphate record

Record type: Article

A geochemical proxy for surface ocean nutrient concentrations recorded in coral skeleton could provide new insight into the connections between sub-seasonal to centennial scale nutrient dynamics, ocean physics, and primary production in the past. Previous work showed that coralline P/Ca, a novel seawater phosphate proxy, varies synchronously with annual upwelling-driven cycles in surface water phosphate concentration. However, paired contemporaneous seawater phosphate time-series data, needed for rigorous calibration of the new proxy, were lacking. Here we present further development of the P/Ca proxy in Porites lutea and Montastrea sp. corals, showing that skeletal P/Ca in colonies from geographically distinct oceanic nutrient regimes is a linear function of seawater phosphate (PO4 SW) concentration. Further, high-resolution P/Ca records in multiple colonies of Pavona gigantea and Porites lobata corals grown at the same upwelling location in the Gulf of Panama were strongly correlated to a contemporaneous time-series record of surface water PO4 SW at this site (r2 = 0.7–0.9). This study supports application of the following multi-colony calibration equations to down-core records from comparable upwelling sites, resulting in ±0.2 and ±0.1 lmol/kg uncertainties in PO4 SW reconstructions from P. lobata and P. gigantea, respectively.

P/Ca Porites lobata (lmol/mol) = (21.1 ? 2.4)PO4 SW (lmol/kg) + (14.3 ? 3.8)

P/Ca Pavona gigantea (lmol/mol) = (29.2 ? 1.4)PO4 SW (lmol/kg) + (33.4 ? 2.7)

Inter-colony agreement in P/Ca response to PO4 SW was good (±5–12% about mean calibration slope), suggesting that species-specific calibration slopes can be applied to new coral P/Ca records to reconstruct past changes in surface ocean phosphate. However, offsets in the y-intercepts of calibration regressions among co-located individuals and taxa suggest that biologically-regulated “vital effects” and/or skeletal extension rate may also affect skeletal P incorporation. Quantification of the effect of skeletal extension rate on P/Ca could lead to corrected calibration equations and improved inter-colony P/Ca agreement. Nevertheless, the efficacy of the P/Ca proxy is thus supported by both broad scale correlation to mean surface water phosphate and regional calibration against documented local seawater phosphate variations.

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Citation

LaVigne, Michele, Matthews, Kathryn A., Grottoli, Andrea G., Cobb, Kim M., Anagnostou, Eleni, Cabioch, Guy and Sherrell, Robert M. (2010) Coral skeleton P/Ca proxy for seawater phosphate: Multi-colony calibration with a contemporaneous seawater phosphate record Geochimica et Cosmochimica Acta, 74, pp. 1282-1293. (doi:10.1016/j.gca.2009.11.002).

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Published date: 2010
Organisations: Geochemistry

Identifiers

Local EPrints ID: 339950
URI: http://eprints.soton.ac.uk/id/eprint/339950
ISSN: 0016-7037
PURE UUID: c89fbe12-1527-4cca-b610-3d78fed1004e

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Date deposited: 06 Jun 2012 10:49
Last modified: 18 Jul 2017 05:50

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Contributors

Author: Michele LaVigne
Author: Kathryn A. Matthews
Author: Andrea G. Grottoli
Author: Kim M. Cobb
Author: Eleni Anagnostou
Author: Guy Cabioch
Author: Robert M. Sherrell

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