MEPS 301:135-148 (2005)  -  doi:10.3354/meps301135

Stable isotopic composition of deep-sea gorgonian corals Primnoa spp.: a new archive of surface processes

Owen A. Sherwood1,*, Jeffrey M. Heikoop2, David B. Scott1, Michael J. Risk3, Thomas P. Guilderson4,5, Richard A. McKinney6

1Centre for Environmental and Marine Geology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada
2Los Alamos National Laboratory, EES-6, MSD462, Los Alamos, New Mexico 87545, USA
3School of Geography and Geology, McMaster University, Hamilton, Ontario L8S 4M1, Canada
4Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
5Department of Ocean Sciences & Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, California 95064, USA
6United States Environmental Protection Agency, Atlantic Ecology Division, Narragansett, Rhode Island 02882, USA

ABSTRACT: The deep-sea gorgonian coral Primnoa spp. live in the Atlantic and Pacific Oceans at depths of 65 to 3200 m. They have an arborescent growth form with a skeletal axis composed of annual rings made from calcite and gorgonin. Lifespans may exceed several hundreds of years. It has been suggested that isotope profiles from the gorgonin fraction of the skeleton could be used to reconstruct long-term, annual-scale variations in surface productivity. We tested assumptions about the trophic level, intra- and inter-colony isotopic reproducibility, and preservation of isotopic signatures in a suite of modern and fossil specimens. Measurements of gorgonin δ15N indicate that Primnoa spp. feed mainly on zooplankton and/or sinking particulate organic matter (POMsink), and not on suspended POM (POMsusp) or dissolved organic carbon (DOC). Gorgonin δ13C and δ15N in specimens from NE Pacific shelf waters, NW Atlantic slope waters, the Sea of Japan, and a South Pacific (Southern Ocean sector) seamount were strongly correlated with surface apparent oxygen utilization (AOU; the best available measure of surface productivity), demonstrating coupling between skeletal isotopic ratios and biophysical processes in surface water. Time-series isotopic profiles from different sections along the same colony, and different colonies inhabiting the same area were identical for δ13C, while δ15N profiles were less reproducible. Similarity in C:N, δ13C and δ15N between modern and fossil specimens suggest that isotopic signatures are preserved over millennial timescales. These results support the use of Primnoa spp. as historical recorders of surface water processes such as biological productivity and the isotopic composition of source nutrients.

KEY WORDS: Primnoa · Gorgonin · δ13C · δ15N · Trophic level · Paleoceanography

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