Interdecadal variation in seawater d13C and d18O recorded in fish otoliths
Limnol. Oceanogr., 54(5), 2009, 1665-1668 | DOI: 10.4319/lo.2009.54.5.1665
ABSTRACT: Stable carbon (δ13C) and oxygen (δ18O) in the otolith cores of Atlantic bluefin tuna (Thunnus thynnus) vary temporally, with changes that quantitatively follow interdecadal variation in atmospheric and oceanic reservoirs. Both carbon and oxygen isotopic signatures vary significantly by year of birth over the range investigated (1947-2006), with δ13C decreasing and δ18O increasing (-2.56 × 10-2‰ and 4.3 × 10-3‰ yr-1, respectively). The rate of change in otolith δ13C was similar to reported rates of atmospheric δ13C depletion, attributed to deforestation and the burning of fossil fuels (referred to as the Suess effect), suggesting a close link between atmospheric and oceanic carbon pools. Increases in otolith δ18O were evident but less pronounced, with observed variation possibly attributable to changing salinity in the Atlantic Ocean. Otolith cores of bluefin tuna effectively track interdecadal trends and record past seawater δ13C and δ18O.