Japan Geoscience Union Meeting 2018

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[JJ] Oral

A (Atmospheric and Hydrospheric Sciences) » A-OS Ocean Sciences & Ocean Environment

[A-OS19] chemical and biological oceanography

Tue. May 22, 2018 10:45 AM - 12:15 PM 105 (1F International Conference Hall, Makuhari Messe)

convener:Tsuneo Ono(Fisheries Research Agency), Namiha Yamada(National Institute of Advanced Industrial Science and Technology), Hiroaki Saito(東京大学大気海洋研究所, 共同), Shin-ichi Ito(Atmosphere and Ocean Research Institute, The University of Tokyo), Chairperson:Ono Tsuneo(Japan Fisheries Research and Education Agency)

11:45 AM - 12:00 PM

[AOS19-05] Seasonal and interannual variations in calcium carbonate saturation state in Tokyo Bay

*Michiyo Yamamoto-Kawai1, Soichiro Ito1 (1.Tokyo University of Marine Science and Technology)

Keywords:Ocean Acidification, Hypoxia, Tokyo Bay

Calcium carbonate saturation state (Ω) was observed at 2 stations in Tokyo Bay from April 2011 to December 2017, on a monthly basis. Ω was high in summer surface water and low in summer bottom water. Biological uptake of CO2 and remineralization of organic matter was a main cause of the seasonal variation of Ω in surface and bottom waters, respectively. Freshwater input and warming/cooling also alters Ω in Tokyo Bay. Aragonite undersaturation was observed in bottom water in August 2013 and July 2014. These coincided with periods when hypoxic condisions were observed for about 2 weeks. Analysis of pCO2 and AOU indicate that undersaturation was caused by regeneration of massive organic matter, including denitrification process. This study revealed seasonal and interannual variations in Ω and their controlling factors. It was also found that benthic organisms in Tokyo Bay has been already experiencing episodic aragonite undersaturation.