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

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