講演情報
[T7-P-18]Unlocking Climate Signals in Japanese Deep-Sea Coral (Corallium japonicum) Using Non-Parametric Rhythmicity Analysis
*Ma. Marivic Capitle Pepino1, Tomoyo Okumura1 (1. Marine Core Research Institute, Kochi University)
キーワード：
Precious coral、C. japonicum、Paleoceanography、Geochemical Proxy、Rhymicity Analysis
The skeletons of deep-sea precious corals, such as Corallium japonicum, form annual bands that chemically record ambient seawater conditions, possibly offering a valuable archive of environmental change. In oceanographically complex regions like the Ashizuri fishing grounds, influenced by the Kuroshio Current, these corals have the potential to capture the effects of remote climate drivers, including El-Niño and Southern Oscillation (ENSO) and decadal-scale oscillations. This study evaluates the potential of C. japonicum as a high-resolution paleo-proxy by analyzing rhythmic elemental variations within a single colony collected from off Ashizuri, Kochi. We performed LA-ICPMS analysis across three skeletal cross-sections, measuring 16 elements critical for environmental reconstruction. The resulting time series were analyzed using RAIN (Rhythmicity Analysis Incorporating Non-parametric methods), a powerful statistical approach adapted from chronobiology that excels at identifying periodic patterns without assuming simple sinusoidal waveforms (Thaben and Westermark, 2014). Our preliminary analysis showed multiple, distinct periodicities, indicating that the coral is simultaneously recording separate environmental processes. A significant ~5-year cycle, consistent with ENSO frequencies, was identified in the lead isotope 206Pb, primarily within the dark (winter) growth bands. In contrast, a longer ~9-year periodicity was detected in both the temperature proxy Mg/Ca, aligning with decadal-scale ocean variability. Furthermore, an ~11-year cycle in Ti/Ca corresponds well with the solar cycle. While these compelling patterns require further validation by refining the skeletal chronology, they demonstrate the remarkable capacity of C. japonicum to deconvolve distinct environmental signals. This work, the first application of non-parametric rhythmicity analysis to deep-sea corals in Japan. Although the long-term physio-ecological periodicity of this species is not well understood, the results suggest that by analyzing specific elemental and isotopic tracers within different growth bands, C. japonicum skeletons can be used as a high-fidelity archive to separate atmospheric inputs from broader oceanic changes.
Keywords: Precious coral, C. japonicum, Paleoceanography, Geochemical Proxy, Rhymicity Analysis
REF: Thaben PF, Westermark PO (2014). “Detecting Rhythms in Time Series with RAIN.” Journal of Biological Rhythms, 29(6), 391–400. doi:10.1177/0748730414553029.
Keywords: Precious coral, C. japonicum, Paleoceanography, Geochemical Proxy, Rhymicity Analysis
REF: Thaben PF, Westermark PO (2014). “Detecting Rhythms in Time Series with RAIN.” Journal of Biological Rhythms, 29(6), 391–400. doi:10.1177/0748730414553029.
