Ocean Acidification Studies in Coral Reefs of Japan

Abstract

Increasing anthropogenic CO2 emissions cause progressive ocean acidification, reducing the calcium carbonate saturation state and coral reef calcification rate. The future uptake of CO2 by the world ocean is predicted to reduce seawater pH by 0.3–0.5 units over the next few decades, which corresponds to a rate 100 times faster than that observed at any time during the last 20 million years. In this chapter, we discuss the effects of ocean acidification on coral reefs, which have been initially probed by culture experiments at several decreased pH conditions, being subsequently investigated by multiple stress factor experiments and field observations of acidified sites. By considering previous studies, we propose that the evaluation and prediction of future ecosystem dynamics require the development of convenient and inexpensive carbonate chemistry-related field measurement techniques such as pH logging, additionally highlighting the importance of studying two naturally acidified sites in Japan, namely, the Iwotorishima and Shikine Islands.