[B-PT02_1PM1] Biocalcification and the Geochemistry of Proxies

[BPT02-15] Corals at marine volcano of Satsuma iwo-jima: Implication for a new proxy of hydrothermal events and biological adaptati

*Tsuyoshi WATANABE¹, Kanae KAMIMURA¹, Atsuko YAMAZAKI², Kazuto OHMORI¹, Francois LE GUERN³, Shoichi KIYOKAWA⁴ (1.Grad. Sch. of Science, Hokkaido University, 2.AORI, University of Tokyo, 3.CNRS, LSCE (Deceased), 4.Grad. Sch. of Science, Kyushu University)

Keywords:Coral geochemistry, hydrothermal activity, coral adaptation, ocean acidification

Coral cores from massive corals could record marine environmental and ecological changes in their annual bands with monthly temporal resolution in the present and/or the past. We discovered large massive Porites corals living at active volcanic island of Satsuma Io-Jima, located 50 km south from Kyushu area, southern part of Japan. Satsuma Io-Jima provides a unique opportunity to observe marine organism living under extreme environments of volcanic gases emission and different types of hydrothermal activities from sea flower. We collected eleven coral cores from four different conditions around the island to test if corals could record volcanic and hydrothermal activities and how corals could survive in extreme environments such as very low pH condition with CO2 emission. Coral annual bands recorded in x-ray images revealed that these corals have been survived at least during last a few hundreds years. Coral extension rate for the site near hydrothermal vent was significantly small (1-2mm/year) relative to that for general condition of Porites corals (ca. 10-20 mm/year), suggesting that coral growth was influenced by hydrothermal activity. We will demonstrate our preliminary results of geochemical approaches of δ¹⁸O, δ¹³C, Sr/Ca, Mg/Ca, Ba/Ca, and F/Ca in coral skeletons and in surrounding seawater and discuss the possibility for reconstructing the past hydrothermal events and relationship between marine ecosystem and extreme environments at volcanic activity as the analogues for coral adaptation to future ocean acidification.