Faculty of Geo-Environmental Science, Rissho University, Kumagaya, Saitama, Japan.
Institute of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa, Japan.
PeerJ. 2022 Aug 23;10:e13931. doi: 10.7717/peerj.13931. eCollection 2022.
Precious corals belong to the family Coralliidae (Cnidaria, Octocorallia), and their axis, which consists of high magnesian calcium carbonate, has long been used in jewelry. With its low growth rate and long lifespan, precious coral is a representative taxon of the vulnerable marine ecosystem. Due to years of overfishing, coral fishery has become a controversial issue. To estimate the growth rate and clarify the uptake process of trace elements in relation to the growth of the carbonate axis, Japanese red coral () was cultured at a depth of 135 m off Takeshima Island, Kagoshima, Japan for 98 months and analyzed by microscopic X-ray fluorescence/soft X-ray photoabsorption (µ-XRF/XAS) speciation mapping. The growth rate was estimated to be 0.37 mm/year in diameter, and 10-11 growth rings were observed in a cross section of the axis. This estimated growth-rate value is the first ever to be obtained from the culture of Japanese precious coral. The fluctuation in water temperature near the -culture site was recorded for part of the culture period and then compared with the changes in the growth ring and the distribution of trace elements in a cross section of the coral axis during the same period. When the water temperature was increasing, the growth ring was light in color, sulfur and phosphorus concentrations were low, and magnesium was high. Conversely, a dark band in the growth ring, high sulfur and phosphorus, and low magnesium concentrations were observed when the water temperature was decreasing. In a cross section of the coral axis, the distribution of sulfur and magnesium from the center to the surface corresponded, respectively, to dark and light bands in the annual growth ring. Sulfur concentration was high in the dark band and low in the light band, while magnesium was negatively correlated with sulfur.
珍贵珊瑚属于柳珊瑚科（刺胞动物门，八放珊瑚亚纲），其轴由高镁方解石碳酸钙组成，长期以来一直用于珠宝制作。由于生长缓慢、寿命长，珍贵珊瑚是海洋脆弱生态系统的代表性分类群。由于多年来的过度捕捞，珊瑚渔业已成为一个有争议的问题。为了估计生长速度并阐明与碳酸盐轴生长有关的微量元素的吸收过程，在日本鹿儿岛县对马岛以北海域 135 米深处养殖了日本红珊瑚（）98 个月，并通过微区 X 射线荧光/软 X 射线光吸收（µ-XRF/XAS）形态分析进行了分析。估计的生长速度为直径 0.37 毫米/年，在轴的横截面上观察到 10-11 个生长轮。这是首次从日本珍贵珊瑚的养殖中获得的估计生长速度值。在部分养殖期间记录了养殖地点附近的水温波动，并将其与同期生长轮和珊瑚轴横截面上微量元素分布的变化进行了比较。当水温升高时，生长轮颜色较浅，硫、磷浓度较低，镁含量较高。相反，当水温下降时，生长轮中会出现深色带，硫、磷含量较高，镁含量较低。在珊瑚轴的横截面上，从中心到表面的硫和镁分布分别与年度生长轮的深色和浅色带相对应。深色带的硫浓度较高，浅色带的硫浓度较低，而镁与硫呈负相关。
