Isotope Laboratory at the National Isotope Centre in Gracefield,
New Zealand. A description of the protocol used has previously
been reported (Ancelet et al., 2011a). Briefly, using a GVI IsoPrime
mass spectrometer and leucine as a working standard, sample
punches (11 mm in diameter) were combusted at 850 °C under
continuous flow. The resulting CO2 was analyzed by IRMS to yield
δ13C values and TC concentrations could also be determined using
MS signal intensities.