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Marine Ecology Progress Series

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MEPS 397:209-218 (2009)  -  DOI:

Multi-century time-series of 15N and 14C in bamboo corals from deep Tasmanian seamounts: evidence for stable oceanographic conditions

Owen A. Sherwood1,5,*, Ronald E. Thresher2, Stewart J. Fallon3, Diana M. Davies4, Thomas W. Trull2,4

1Department of Earth Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1C 3X9, Canada
2CSIRO Marine and Atmospheric Research and Wealth from Oceans and Climate Adaptation Flagships, Castray Esplanade, Hobart, Tasmania 7000, Australia
3Research School of Earth Sciences, Australian National University, Bldg 61, Mills Road, Acton, Australian Capital Territory 2000, Australia
4Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC) and Institute of Antarctic and Southern Ocean Studies (IASOS), University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia
5Present address: 4 Hipditch Hill, St. John's, Newfoundland A1A 1A5, Canada

ABSTRACT: Bamboo corals (Family Isididae) are an important component of seamount benthos south of Tasmania. Besides having lifespans of up to 400 yr, little is known about their basic ecology, nor how to decode potential climate signals encoded in their skeletons. We explored the stable nitrogen isotope and radiocarbon compositions of the skeletal organic fraction of the genera Isidella, Keratoisis and Lepidisis collected from 3 Tasmanian seamounts. Analyses were performed on tissues and organic node growth rings sampled at a temporal resolution of 1 to 4 yr. Radiocarbon chronologies exhibited nuclear bomb signals characteristic of surface waters and constrained radial growth rates to ~35 ± 10 µm yr–1 for 3 specimens of the genus Lepidisis and 113 ± 17 µm yr–1 for 1 specimen of Isidella. δ15N values of the living tissue and underlying gorgonin were similar and averaged 9 to 12‰. Records of δ15N from 8 different specimens showed subtle, quasi-decadal patterns over the last ~100 yr, although the amplitude of these features (~1‰) was similar to the average intra- and intercolony reproducibility. These results demonstrate the utility of deep-sea corals to track seamount biogeochemical processes over long time scales, and suggest that the extent of nutrient depletion of surface waters and associated trophic dynamics have remained relatively constant in this region over centuries. This provides an important baseline for the evaluation of the impacts of anthropogenic climate change.

KEY WORDS: Tasmanian seamounts · Deep-sea corals · Stable isotopes · Radiocarbon · Biogeochemistry

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Cite this article as: Sherwood OA, Thresher RE, Fallon SJ, Davies DM, Trull TW (2009) Multi-century time-series of 15N and 14C in bamboo corals from deep Tasmanian seamounts: evidence for stable oceanographic conditions. Mar Ecol Prog Ser 397:209-218.

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