Japan Geoscience Union Meeting 2014

Presentation information

Oral

Symbol B (Biogeosciences) » B-BG Biogeosciences & Geosphere-Biosphere Interactions

[B-BG21_1AM1] Material cycles in tropical- subtropical coastal ecosystems

Thu. May 1, 2014 9:00 AM - 10:30 AM 213 (2F)

Convener:*Atsushi Watanabe(Department of Mechanical and Environmental Informatics Graduate School of Information Science and Engineering Tokyo Institute of Technology), Kazuhiko Fujita(Department of Physics and Earth Sciences, University of the Ryukyus), Chuki Hongo(Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus), Chair:Atsushi Watanabe(Department of Mechanical and Environmental Informatics Graduate School of Information Science and Engineering Tokyo Institute of Technology), Kazuhiko Fujita(Department of Physics and Earth Sciences, University of the Ryukyus), Chuki Hongo(Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus)

9:00 AM - 9:15 AM

[BBG21-01] Ocean Acidification and its effect on calcification since the late 19th century revealed by d11B of Ogasawara coral

*Kaoru KUBOTA1, Yusuke YOKOYAMA1, Tsuyoshi ISHIKAWA2, Atsushi SUZUKI3 (1.Atmosphere and Ocean Research Institute, University of Tokyo, 2.Japan Agency for Marine-Earth Science and Technology, 3.National Institute of Advanced Industrial Science and Technology)

Keywords:boron, Ogasawara, coral, calcification, Ocean Acidification

Boron isotopes (d11B) of coral skeleton are known as a pH meter in the seawater. As pH of seawater is closely related to partial pressure of CO2 (pCO2) in the atmosphere, it is expected that d11B becomes pCO2 indicator in the geological past too. However, d11B-pH is under scrutinized since coral calcification itself probably affects the relationship. Although many studies have focused on d11B measurements for cultured corals under pH-controlled aquarium, those for living corals outdoors have rarely measured, which are limited to, for example, Great Barrier Reef and Guam. Here we show 125 years-records (AD1873-1998) of d11B and boron concentration (B/Ca ratio) for long-lived massive coral (Porites sp.) that was sampled at Chichi-jima, Ogasawara Islands, North West Pacific. They clearly reveal Ocean Acidification after the industrial revolution. We will discuss a relationship between ocean acidification and coral calcification from a slope of pH decline that is obtained from observational data. We will also discuss how B/Ca of calcium carbonate skeleton that is produced by marine calcifiers is reliable proxy for seawater pH, which is being paid a great attention mainly due to relative easiness to measure compared to isotopes.