Isotopic composition of carbonate-bound organic nitrogen in deep-sea scleractinian corals: A new window into past biogeochemical change

XT Wang, MG Prokopenko, DM Sigman… - Earth and Planetary …, 2014 - Elsevier
Earth and Planetary Science Letters, 2014Elsevier
Over the last two decades, the skeletal remains of deep-sea corals have arisen as a
geochemical archive of Pleistocene oceanographic change. Here we report the exploration
of the isotopic composition of the carbonate-bound organic nitrogen (hereafter, CB-δ 15 N)
in the deep-sea scleractinian coral Desmophyllum dianthus as a possible tool for
reconstructing past changes in the ocean nitrogen cycle. The measurement protocol is
adapted from a high-sensitivity method for foraminifera shell-bound δ 15 N. We explored the …
Over the last two decades, the skeletal remains of deep-sea corals have arisen as a geochemical archive of Pleistocene oceanographic change. Here we report the exploration of the isotopic composition of the carbonate-bound organic nitrogen (hereafter, CB-δ 15 N) in the deep-sea scleractinian coral Desmophyllum dianthus as a possible tool for reconstructing past changes in the ocean nitrogen cycle. The measurement protocol is adapted from a high-sensitivity method for foraminifera shell-bound δ 15 N. We explored the variability of CB-δ 15 N within specimens, among corals collected at different depths in a given ocean region, and among different ocean regions. Modern D. dianthus CB-δ 15 N is strongly correlated with the δ 15 N of N export as estimated from sediment traps, shallow subsurface nitrate, and surface sediments, suggesting that CB-δ 15 N is a reliable proxy for δ 15 N of N export. D. dianthus CB-δ 15 N is consistently 8–9‰ higher than δ 15 N of N export, indicating that D. dianthus acquires its nutrition primarily from suspended particulate organic matter (POM) that derives from sinking POM, not directly from sinking POM.
Elsevier
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