Woods Hole Oceanographic Institution

Kelton McMahon

»Deep-sea coral export production
»Ocean Ecogeochemistry
»Estimating movement of marine animals
»Functional connectivity in a coral reef seascape
»Carbon isotopes identify snapper nursery habitat
»Otolith amino acid carbon isotope method
»Amino acid fractionation in fish tissues
»Stable isotope fractionation in fish muscle and otoliths
»Transequatorial Migrations by Basking Sharks
»Tracking top predator migration with isoscapes
»Bivalves as bioproxies for climate change
»Serries groenlandicus
»Digestibility of Ice algae and Phytoplankton
»Salt marsh fish movement and trophic dynamics

Schiff JT, Batists FC, Sherwood OA, Guilderson TP, Hill TM, Ravelo AC, McMahon KW, McCarthy MD, Compound specific amino acid δ13C patterns in a deep-sea proteinaceous coral: Implications for reconstructing detailed δ13C records of exported primary production, Marine Chemistry, 166: 82-91, 2014

Deep-sea proteinaceous corals represent high-resolution paleoarchives, extending biogeochemical time series far beyond recent instrumental data. While recent studies have applied compound specific amino acid δ15N (δ15N-AA) measurements of their organic skeletal layers to investigate Holocene nitrogen cycling, potential applications of amino acid δ13C (δ13C-AA) in proteinaceous corals have not yet been examined. Here we developed δ13C-AA analysis in deep-sea bamboo coral (Isidella sp.) from theMonterey Canyon to reconstruct exported primary production over an ~80 year record. Preserved deep-sea coral essential amino acid δ13C-AA patterns (δ13C-EAA) closelymatched those expected fromnatural and cultured phytoplankton, supporting the hypothesis that deep-sea coral δ13C-EAA values represent unaltered signatures of exported primary production sources. The coral bulk δ13C record showed cyclic 0.5‰ variations over the last century,with a shift to lower δ13C values in the early 1960s. Variations in coral δ13C-EAA values closely followed bulk δ13C signatures, although both the range and the magnitude of change in the bulk δ13C record were highly attenuated compared to the δ13C-EAA record. Our results indicate that δ13C-EAA in proteinaceous corals represent a new, direct proxy for δ13C in primary production that is more sensitive and accurate than bulk δ13C. To test this idea, we used existing phytoplankton δ13C-AA data to calculate an offset between bulk δ13C and δ13C-EAA. When applied to our data, a reconstructed record of δ13C values for exported organic matter was consistent with regional phytoplankton dynamics and expected trophic transfer effects, suggesting significant AA resynthesis only in the non-essential AA pool. Together, these results indicate that δ13C-EAA in deep-sea proteinaceous corals provide a powerful new long-term, high resolution tool for investigating variations in exported primary production and biogeochemistry.

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