Ocean acidification from CO2 absorption is altering marine chemistry in ways that directly affect the physiology and welfare of fish, invertebrates, and other marine animals.
Ocean acidification creates welfare harms through multiple mechanisms. For calcifying organisms — oysters, mussels, sea urchins, corals — shell or skeleton building becomes energetically costly and sometimes impossible at current and projected pH levels, causing developmental problems and increased vulnerability to predation and disease. Fish exposed to elevated CO2 show disrupted olfactory function, altered risk assessment, and changes in lateralization that affect predator avoidance. The welfare impacts of ocean acidification affect billions of individual animals across ecosystems and will intensify without dramatic reductions in CO2 emissions.