Skeletal P/Ca tracks upwelling in Gulf of Panamá coral: Evidence for a new seawater phosphate proxy

Abstract

[1] The supply of limiting nutrients to the low latitude ocean is controlled by physical processes linked to climate variations, but methods for reconstructing past nutrient concentrations in the surface ocean are few and indirect. Here, we present laser ablation mass spectrometry results that reveal annual cycles of P/Ca in a 4-year record from the scleractinian coral Pavona gigantea (mean P/Ca = 118 mmol mol À1 ). The P/Ca cycles track variations in past seawater phosphate concentration synchronously with skeletal Sr/Ca-derived temperature variations associated with seasonal upwelling in the Gulf of Panamá. Skeletal P/Ca varies seasonally by 2 -3 fold, reflecting the timing and magnitude of dissolved phosphate variations. Solution cleaning experiments on drilled coral powders show that over 60% of skeletal P occurs in intracrystalline organic phases. Coral skeleton P/Ca holds promise as a proxy record of nutrient availability on time scales of decades to millennia.

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

“…The skeletal element ratio P/Ca was shown to track annual upwelling cycles in a single Pavona gigantea coral over a 4-year record (LaVigne et al, 2008). This study also revealed that $90% of coral skeleton P is incorporated as an intracrystalline phase resistant to solution cleaning of finely ground coral aragonite.…”

“…Multi-year P/ Ca records were averaged to acquire mean skeletal P/Ca for two Montastrea faveolata (Biscayne National Park, FL; and Martinique, Caribbean) and five Porites lutea (Gulf of Aqaba/Eilat, Red Sea; Rarotonga and New Caledonia, South Pacific; Christmas Island and Fanning Island, Central Equatorial Pacific) colonies (Table 1; Linsley et al, 2000;Desenfant, 2004 ;Nurhati et al, 2009). Since skeletal P sampled below the organic tissue layer has been shown to be resistant to rigorous chemical cleaning (LaVigne et al, 2008), the powders extracted from distilled-water rinsed slabs were not cleaned chemically prior to analysis for the globally distributed samples. Mean P/Ca values for Montastrea sp.…”

“…Multi-colony P/Ca calibration with in situ PO 4 SW concentration Sufficient evidence has now been presented both in global distribution and down-core periodicity (LaVigne et al, 2008) to warrant additional testing of the hermatypic coral P/Ca-PO 4 SW proxy. Natural P/Ca variability among co-located coral colonies and species-specific calibrations with contemporaneous seawater data was therefore assessed.…”

Inductively coupled plasma- and glow discharge plasma-sector field mass spectrometry : Part II. Applications

“…[165][166][167][168][169][170][171] The latter sample materials can reflect the environmental status in water in their element/Ca ratios. 172 Sea water temperatures can be calculated from Mg/Ca ratios in foraminifera since the uptake of Mg into foraminiferal CaCO 3 is temperature-dependent.…”

“…The resulting nitrocellulose membranes were concomitantly incubated with a mixture of DOTA-lanthanide-labelled antibodies, i.e. 165 Ho-anti-BSA, 159 Tb-anti-casein and 169 Tm-antilysozyme and finally subjected to LA-ICP-SFMS. The lanthanide-specific signals were colour-coded and plotted (see Fig.…”