The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Cold-water bamboo corals are potential high-resolution archives of environmental variability and the growth history of cold-water corals in deep ocean. However, obtaining accurate, high-resolution chronology of bamboo corals are still challenging. In this study, live-collected bamboo corals from northwest South China Sea (SCS) were used for radiocarbon analysis, growth ring counting and Sr/Ca measurement. Radiocarbon analysis of organic nodes display typical bomb ¹⁴C curve, suggesting that the food source of the bamboo corals in NW SCS mainly derive from the freshly sinking particulate organic carbon (POC) from the surface ocean. The obtained coral ages via comparison of the bomb ¹⁴C curves between the bamboo coral and tropical corals are strongly correlated with the growth ring number, displaying growth-ring formation rate of ~6 and ~2 rings/years. These growth-ring formation rates are approximately same as the POC export frequency at respective water depths. In analogue to the modern environmental setting with periodic food availability to the corals, the growth rings formation is proposed to be controlled by the frequency of food availability to the corals. Furthermore, the growth ring number of the organic nodes were found to be ~ 2 times the Sr/Ca oscillation number of calcite internode for all the corals, indicating the potential of Sr/Ca oscillation number for accurate, high-resolution chronology establishment. With the Sr/Ca based chronology, coral annual radial growth rates (RGR) were obtained. All the detrended coral annual RGR display strong correlation with the East Asian Winter Monsoon and ENSO at interannual timescales (correlation coefficient: 0.7), clearly supporting the accurate, high-resolution chronology of bamboo corals via counting Sr/Ca oscillation number. In summary, our results clearly suggest that combination of the radiocarbon analysis, the growth ring counting and the Sr/Ca oscillation number to be used for obtaining accurate, high-resolution chronology of bamboo corals.