Adapted by Ministry for the Environment and Stats NZ to provide for environmental reporting transparency. Dataset used to develop the "Ocean acidification" indicator (available at https://www.stats.govt.nz/indicators/ocean-acidification). This data set measures the change in pH in subantarctic surface waters at a station east of Otago from 1998 to 2020. Ocean acidification describes the long-term decrease in the pH of our oceans and coastal waters. This indicator measures: - change in pH, acidity and pCO2 (a measure of dissolved carbon dioxide) in New Zealand’s subantarctic surface waters (Munida Transect) from 1998 to 2020. More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.