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MEPS 335:85-94 (2007)  -  doi:10.3354/meps335085

Oceanographic changes in the North Pacific Ocean over the past century recorded in deep-water gorgonian corals

Branwen Williams1,4,*, Mike Risk2, Robert Stone3, Daniel Sinclair1, Bassam Ghaleb1

1GEOTOP, Université du Québec à Montréal (UQAM)-McGill, CP 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
2McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada
3NMFS Auke Bay Laboratory, 11305 Glacier Highway, Juneau, Alaska 99801, USA
4Present address: School of Earth Sciences, Ohio State University, Columbus, Ohio 43210, USA

ABSTRACT: Deep-water gorgonian corals are long-lived and abundant in the North Pacific Ocean. Gorgonians have annually-resolved skeletal organic bands, making them proxies of environmental changes. Specimens of Primnoa sp. were collected from the Gulf of Alaska in 2001, 2003, and 2004. Organic band counts and 210Pb dating were combined to produce a growth chronology for 2 specimens. Organic skeletal growth bands were dissected and analysed for 13C and 15N to investigate long-term changes in production and cycling of organic matter in surface waters. Three specimens were analyzed: PAL, P26 and P88. Specimen PAL, with a record spanning 125 yr, exhibits a statistically significant systematic depletion of 13C and 15N over time. The magnitude of the depletion trend in the carbon record over the past 50 yr is equivalent to the 13C depletion of ocean surface dissolved inorganic carbon from the input of anthropogenic carbon into the atmosphere (the Suess effect). The depletion in 15N may reflect changes in plankton composition at the bottom of the food web.

KEY WORDS: Deep-water corals · North Pacific · Stable isotopes · Biogeochemistry

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