Ocean Acidification. In: OSPAR, 2023: The 2023 Quality Status Report for the North-East Atlantic

Every year the ocean absorbs at least a quarter of the carbon dioxide (CO2) released to the atmosphere from burning of fossil fuels, cement production and land use change. This is driving ocean acidification. This assessment represents the first OSPAR assessment of Ocean Acidification in the North-East Atlantic and addresses trends and variability, projections of future acidification, impacts on ecosystems and ecosystem services and mitigation and adaption. Key findings are given below. 1. Ocean acidification has been observed in all OSPAR Regions during the past decades. It is projected to keep occurring and even accelerate under the higher carbon dioxide (CO2) emission scenarios. 2. The rate at which ocean acidification occurs varies geographically and throughout the water column. This variability is particularly evident in coastal environments due to the complex interactions of local physical, chemical and biological processes. 3. Ocean acidification is a major threat to marine species and ecosystems, with direct consequences to ecosystem services. Studies on biological impacts have indicated that there will be clear changes in organisms’ structure, distribution, and ability to function as a result of ocean acidification effects. 4. Threatened and / or declining species and habitats, for example cold water coral reefs Lophelia pertusa, are particularly vulnerable to changing environmental conditions, including ocean acidification, and evidence suggests that some commercially important species may also be negatively impacted by these effects. 5. Ocean acidification effects interact with other pressures from environmental change and ecological interactions. The ability of species to adapt to ocean acidification will depend on the rate of environmental change, evolutionary processes and for most species, the present standing genetic variation. 6. Our understanding of trends, variability, drivers, and ecological impact of ocean acidification needs to improve. This requires better harmonised and tailored monitoring and data integration, further integration of observations and model products, and an ongoing multi-strand research effort to better predict impacts. 7. Climate change mitigation and adaptation responses are in many cases also effective against ocean acidification, but some proposed responses may also exacerbate ocean acidification and its impacts. Report available at: https://oap.ospar.org/en/ospar-assessments/quality-status-reports/qsr-2023/other-assessments/ocean-acidification