15:45 〜 16:00
[BPT03-07] Elemental Profiles of a Japanese Precious Coral skeleton, Corallium japonicum :
new insights from an alive colony
キーワード：Corallium japonicum、precious coral、elemental profile、growth kinetics、environmental influence
Precious coral corals around Japan grow slowly in relatively deep waters (>80 m), are believed to have a long-life span of over 100 years, but their growth and physiological ecology remain a mystery. To elucidate the interplay between growth and environmental factors, we analyzed the chemical composition of a live Corallium japonicum colony skeleton (PC1-3) in 2017 from the Ashizuri fishing field at a depth range of 118m – 124m, influenced by the Kuroshio Current. Unlike previous studies, which often focused on limited elemental twin or single cross-sections, potentially overlooking vertical variations in growth and elemental incorporation, we comprehensively assessed elemental compositions across three skeletal cross-sections collected at varying heights along the colony axis. Using a LA-ICP-MS, we measured 15 elemental correlated concentrations and these with growth layers in medullar (core) and annular (outer) regions within the skeletons. By comparing measurement data with 30 years of local environmental data, we assessed the external factors modulating coral growth.
Our results revealed distinct chemical signatures between medullar and annular regions, with variations in Na, Mg, Sr, U, Ti, Mn, Ba, and Pb suggesting different growth mechanisms. Elemental gradients along the vertical axis indicated increased incorporation of calcification-related elements toward the apical tip, consistent with faster medullar growth, which also showed increased size from base to tip. implicit, Cu and Pb decreased with growth, potentially due to metabolic exclusion. Within the annular region, elemental incorporation varied across growth bands, with faster-growing light bands exhibiting higher concentrations of carbonate-related elements (Na, Mg, Sr; p<0.001) but also Pb isotopes (p<0.05). The unexpectedly higher S/Ca ratio in light bands contradicted previous findings, warranting further investigation. Despite seasonal SST variations (18-27°C) and dynamic water currents driven by the Kuroshio, direct correlations between these environmental parameters and elemental concentrations were weak. This suggests that growth kinetics, rather than direct environmental parameters, exert a primary control on skeletal chemistry. While currents may still indirectly influence growth via nutrient supply and sediment removal, their direct impact on elemental incorporation limited.
Our findings appear emphasize the dominance of growth-related processes over direct environmental forcing in determining C. japonicum skeletal chemistry. These insights improve coral-based paleoenvironmental reconstructions, enhance our understanding of modern physiology, offer valuable data for optimizing coral restoration efforts by providing a baseline for assessing site suitability and post-transplantation monitoring, and ultimately contribute to sustainable management of precious coral populations.
Our results revealed distinct chemical signatures between medullar and annular regions, with variations in Na, Mg, Sr, U, Ti, Mn, Ba, and Pb suggesting different growth mechanisms. Elemental gradients along the vertical axis indicated increased incorporation of calcification-related elements toward the apical tip, consistent with faster medullar growth, which also showed increased size from base to tip. implicit, Cu and Pb decreased with growth, potentially due to metabolic exclusion. Within the annular region, elemental incorporation varied across growth bands, with faster-growing light bands exhibiting higher concentrations of carbonate-related elements (Na, Mg, Sr; p<0.001) but also Pb isotopes (p<0.05). The unexpectedly higher S/Ca ratio in light bands contradicted previous findings, warranting further investigation. Despite seasonal SST variations (18-27°C) and dynamic water currents driven by the Kuroshio, direct correlations between these environmental parameters and elemental concentrations were weak. This suggests that growth kinetics, rather than direct environmental parameters, exert a primary control on skeletal chemistry. While currents may still indirectly influence growth via nutrient supply and sediment removal, their direct impact on elemental incorporation limited.
Our findings appear emphasize the dominance of growth-related processes over direct environmental forcing in determining C. japonicum skeletal chemistry. These insights improve coral-based paleoenvironmental reconstructions, enhance our understanding of modern physiology, offer valuable data for optimizing coral restoration efforts by providing a baseline for assessing site suitability and post-transplantation monitoring, and ultimately contribute to sustainable management of precious coral populations.