The ocean around New Zealand is getting more acidic, potentially causing widespread harm to marine life, data has revealed.
The Stats NZ report, based on NIWA data, showed acidity has increased 8.6 percent between 1998 and 2020.
It's caused by the ocean absorbing carbon dioxide from the air, which can dissolve the shells of pāua, mussels and other kaimoana.
NIWA principal marine biogeochemist Dr Cliff Law said the increase is "alarming", but the trend has been observed for some time.
Ocean acidity has increased by 30 percent over the last 250 years, and will increase by up to 150 percent by the end of the century, Law said.
Stats NZ and the Ministry for the Environment will take a deeper look into the state of Aotearoa's coastlines and ocean with the release of the next Our Marine Environment report in October.
Oceans are a large carbon sink and are likely to have absorbed 20-30 percent of the carbon dioxide emitted by human activities in the last two decades.
Acidification may cause widespread harm to ecosystems, by reducing the concentration of carbonate ions which, along with calcium ions, are the building blocks for the skeletons and shells of many marine organisms, the study said.
