evidence: See all EU institutions and bodiesAlmost one quarter of human-caused carbon dioxide (CO2) emissions are absorbed by oceans, resulting in ocean acidification, i.e. a decrease in the ocean water pH. Ocean acidification has increased rapidly causing pH to drop by approximately 30% since the pre-industrial era. Further decreases in pH are projected in the future. Seawater pH has decreased from 8.11 in 1985 to 8.05 in 2021. Ocean acidification has impacts on marine organisms with its effects cascading throughout the food web, modifying ecosystem services like fisheries. [...] Over the last million years, mean surface seawater pH has been relatively stable. Oscillating between 8.3, during cold periods (e.g. during the last glacial maximum 20,000 years ago), and 8.2, during warm periods (e.g. just prior to the industrial revolution). Rapid increases in atmospheric CO2 levels due to emissions from human activities are now threatening this stability, as a large fraction of emitted CO2 is absorbed by the ocean, causing a decline in pH and subsequent ocean acidification. [...] Mean surface ocean pH is projected to decline further, between about 0.15 and 0.5pH units by 2100 depending on the emission scenario. This will affect many marine organisms and could alter marine ecosystems. In the North Atlantic Ocean, cold water corals are expected to face severe impacts due to acidification and losses of carbonate skeleton.