The Suess effect in Fiji coral δ13C and its potential as a tracer of anthropogenic CO2 uptake

► Long-term decreasing trend in coral δ13C is due to the atmospheric 13C Suess effect. ► Fiji Porites corals growing at deeper water depths have lower mean δ13C. ► Fiji Porites corals growing at deeper water depths have lower skeletal extension rates. ► The growth of corals into shallower water with time dampens the δ13C trend. ► The trend in coral δ13C lags the trend in atmospheric CO2 δ13C by ~ 10 years.