In solution at 25 °C, a pH of 7 indicates neutrality (i.e. the pH of pure water) because water naturally dissociates into H+ and OH− ions with equal concentrations of 1×10−7 mol/L.

That is, the solubility of Mg and Ca will change differently as CO2 dissolvess in water, and you have told us that foraminifera amplify the differences in solubility.

Those whom the Gods wish to destroy They first make mad. -- Euripides

This reminds me of Stephen Jay Gould.

In many places -- the atolls of the Pacific, the shrimp beds of the Eastern Seaboard, the fiords of Norway -- some of the most advanced forms of ocean life are struggling to survive while the most primitive are thriving and spreading. Fish, corals and marine mammals are dying while algae, bacteria and jellyfish are growing unchecked. Where this pattern is most pronounced, scientists evoke a scenario of evolution running in reverse, returning to the primeval seas of hundreds of millions of years ago.

Jeremy B.C. Jackson, a marine ecologist and paleontologist at the Scripps Institution of Oceanography in La Jolla, says we are witnessing "the rise of slime."

For many years, it was assumed that the oceans were too vast for humanity to damage in any lasting way. "Man marks the Earth with ruin," wrote the 19th century poet Lord Byron. "His control stops with the shore."

Even in modern times, when oil spills, chemical discharges and other industrial accidents heightened awareness of man's capacity to injure sea life, the damage was often regarded as temporary.

But over time, the accumulation of environmental pressures has altered the basic chemistry of the seas.

The causes are varied, but collectively they have made the ocean more hospitable to primitive organisms by putting too much food into the water.

Industrial society is overdosing the oceans with basic nutrients -- the nitrogen, carbon, iron and phosphorous compounds that curl out of smokestacks and tailpipes, wash into the sea from fertilized lawns and cropland, seep out of septic tanks and gush from sewer pipes.

Modern industry and agriculture produce more fixed nitrogen -- fertilizer, essentially -- than all natural processes on land. Millions of tons of carbon dioxide and nitrogen oxide, produced by burning fossil fuels, enter the ocean every day.

These pollutants feed excessive growth of harmful algae and bacteria.

At the same time, overfishing and destruction of wetlands have diminished the competing sea life and natural buffers that once held the microbes and weeds in check.

The consequences are evident worldwide.

Off the coast of Sweden each summer, blooms of cyanobacteria turn the Baltic Sea into a stinking, yellow-brown slush that locals call "rhubarb soup." Dead fish bob in the surf. If people get too close, their eyes burn and they have trouble breathing.

Eurolanders may be experiencing this devolution as a plague of jellyfish

Destroying the coral nurseries in which the larger, more complex species hatch and feed as juveniles can only exacerbate the process....

the blog Shifting Baselines comments fairly frequently on the death-watch for the world's oceans, and the grim determination of the Corporate PRess to "Keep False Hope Alive" by running repetitive upbeat disinformation to camouflage the true extent of the problem -- or periodic alarmist op/eds which always conclude with some cheery Energy Fairy story about science saving us or it being "too soon to tell" what's really going on.

[What's really going on is exterminism, the conversion of all biotic complexity on earth into inedible monopoly counters, i.e. "money".]

He also comments perspicaciously on the phenomenon for which his site is named, i.e. that with the hypermobility of the cheap fossil fuel age comes a loss of human continuity in bioregions:  such a large percentage of people in most coastal areas are newcomers that they have no memory of even 10 years ago, let alone a generation ago, and thus no sense of the extent and rate of damage and loss in local biotic systems, watersheds, etc.  The baseline is constantly shifting:  beach closures become normal, fisheries disappear and condos sprout, food comes from further and further away... I live on Monterey Bay, once a thriving salmon and sardine fishery, and the fish in my local fresh-food market is airlifted (let's call it what it is, even if "the market" drives it rather than a government programme) in from the Philippines and Hawaii and VietNam -- but this is "perfectly normal" to a 20 y.o. college student who just moved here.

[The energy cost of this food airlift necessitated by the coring-out and liquidation of food resources closer to home will only get higher over time.]

The shifting baseline makes it very difficult to mobilise social/political action to preserve biotic resources from piracy and vandalism or to repair the damage, since everything looks "just fine" to the newcomers -- who may be a majority of the population and may well have relocated from someplace even more damaged.  The "things were better in my day" grumbling from old-timers will be dismissed as just that, nostalgic grumbling -- even if every word of it is an accurate accounting of possibly-irretrievable loss of carrying capacity.

[The glut of cheap fossil fuel in a social system appears to have effects strangely analogous to the effects of hypernutrition in a biotic system -- the defeat of checks and balances and runaway hypertrophism.  We know how the story ends for a pond or a yeast culture -- or an ocean.]

The difference between theory and practise in practise ...