The scare term “ocean acidification” first popped up in Nature in 2003, followed by the Royal Society in 2005, and has since been seized on as a substitute frightener, given that global warming has stalled. Climate scientists now “calculate” that the average ocean alkalinity has declined from 8.2 to 8.1 on the scale since pre-industrial times, except that the measurement error margin is several times the alleged reduction (and each of the five oceans has its own pH characteristics). pH levels at given points can also swing markedly even within the 24-hour cycle.
In past geological ages C02 levels in the atmosphere were ten or more times what they are now (400ppm) and ocean life thrived. Indeed our current fossil fuels are the residue of vast oceanic life that thrived and died in such super-high CO2 environments.
In the parts of the oceans where alkalinity is low (i.e. tending towards neutral), fish, corals, and sea flora have managed and adapted perfectly well. Freshwater lakes and rivers are slightly acidic (pH of 6 to 8), as is rainwater, pH 5.6, and drinking water, 6.5 to 7.5. Life has adapted and thrives in fresh water notwithstanding the, ahem, “acidification”.