HR: 0800h
AN: B21B-0876    [Abstracts]
TI: A Century of Surface Productivity Recorded in the Skeleton of a Deep-Sea Coral.
AU: * Williams, B
EM: branwenw01@yahoo.ca
AF: GEOTOP, University of Quebec at Montreal, C.P. 8888, succursale Centre-Ville, Montreal, QC H3C 3P8 Canada
AU: Risk, M J
EM: riskmj@univmail.cis.mcmaster.ca
AF: School of Geography and Geology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1 Canada
AU: Stone, R
EM: Bob.Stone@noaa.gov
AF: NOAA, National Marine Fisheries Service, Auke Bay Laboratory, 11305 Glacier Highway, Juneau, AK 99801-8626 United States
AB: "Poor understanding of the nutrient dynamics in the Gulf of Alaska results from insufficient uninterrupted, long-term observations" (PICES, 2004). Failing an instrumental record, oceanographers must increasingly rely on proxies. The utilization of deep-water corals as environmental recorders has only recently been recognized: they may fill in the many gaps present in instrumental records. {\it Primnoa} spp. is a long-lived gorgonian coral common in the northeastern Pacific. The abundance levels of \delta$^{15}$N and \delta$^{13}$C in the gorgonin portion of the skeleton have been correlated to surface productivity (Sherwood et al, 2004). {\it Primnoa} spp. can consequently be used as an historical proxy of productivity. A {\it Primnoa} specimen was obtained from 58.38 N and 148.77 W in the Gulf of Alaska. The coral was dead when collected, and died sometime after bomb testing, in the mid-1950's. Its lifespan was more than 100 years. Annual banding in the skeleton is quite clear, allowing tight dating control. Isotopic abundances of \delta$^{15}$N ranged from 10.2 to 14.4, suggesting the specimen was carnivorous, feeding primarily on zooplankton. Levels of \delta$^{13}$C ranged from -17.7 to -19.4, and exhibit decadal cyclical characteristic of the decadal patterns in the Gulf of Mexico. By matching cycles in isotopic abundances with historical data, we have been able to estimate time of death. This one coral specimen therefore extends the instrumental record by approximately 70 years.
DE: 4870 Stable isotopes
DE: 4267 Paleoceanography
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting