Marine calcifiers are one of the most abundant organisms to produce carbonate on Earth. Evaluation of their response on ocean acidification is commonly sought for worldwide as ocean acidification has progressed globally. JAMSTEC has succeeded in developing new technique to quantify the carbonate density of marine calcifierfs test using MXCT. JAMSTEC has also collaborated with domestic and overseas academic organizations to promote broadly MXCT technique as the best evaluation method for ocean acidification response of marine calcifiers.