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3 " Ocean Acidification is sometimes referred to as Global Warming's Equally Evil Twin. The irony is intentional and fair enough as far as it goes... No single mechanism explains all the mass extinctions in the record and yet changes in ocean chemistry seem to be a pretty good predictor. Ocean Acidification played a role in at least 2 of the Big Five Extinctions: the End-Permian and the End-Triassic. And quite possibly it was a major factor in a third, the End-Cretaceous. ...Why is ocean acidification so dangerous? The question is tough to answer only because the list of reasons is so long. Depending on how tightly organisms are able to regulate their internal chemistry, acidification may affect such basic processes as metabolism, enzyme activity, and protein function. Because it will change the makeup of microbial communities, it will alter the availability of key nutrients, like iron and nitrogen. For similar reasons, it will change the amount of light that passes through the water, and for somewhat different reasons, it will alter the way sound propagates. (In general, acidification is expected to make the seas noisier.) It seems likely to promote the growth of toxic algae. It will impact photosynthesis—many plant species are apt to benefit from elevated CO2 levels—and it will alter the compounds formed by dissolved metals, in some cases in ways that could be poisonous.

Of the myriad possible impacts, probably the most significant involves the group of creatures known as calcifiers. (The term calcifier applies to any organism that builds a shell or external skeleton or, in the case of plants, a kind of internal scaffolding out of the mineral calcium carbonate.)...

Ocean acidification increases the cost of calcification by reducing the number of carbonate ions available to organisms that build shells or exoskeletons. Imagine trying to build a house while someone keeps stealing your bricks. The more acidified the water, the greater the energy that’s required to complete the necessary steps. At a certain point, the water becomes positively corrosive, and solid calcium carbonate begins to dissolve. This is why the limpets that wander too close to the vents at Castello Aragonese end up with holes in their shells.

According to geologists who work in the area, the vents have been spewing carbon dioxide for at least several hundred years, maybe longer. Any mussel or barnacle or keel worm that can adapt to lower pH in a time frame of centuries presumably already would have done so. “You give them generations on generations to survive in these conditions, and yet they’re not there,” Hall-Spencer observed. "

Elizabeth Kolbert , The Sixth Extinction: An Unnatural History

17 " He imagined a town called A. Around the communal fire they’re shaping arrowheads and carving tributes o the god of the hunt. One day some guys with spears come over the ridge, perform all kinds of meanness, take over, and the new guys rename the town B. Whereupon they hang around the communal fire sharpening arrowheads and carving tributes to the god of the hunt. Some climatic tragedy occurs — not carving the correct tributary figurines probably — and the people of B move farther south, where word is there’s good fishing, at least according to those who wander to B just before being cooked for dinner. Another tribe of unlucky souls stops for the night in the emptied village, looks around at the natural defenses provided by the landscape, and decides to stay awhile. It’s a while lot better than their last digs — what with the lack of roving tigers and such — plus it comes with all the original fixtures. they call the place C, after their elder, who has learned that pretending to talk to spirits is a fun gag that gets you stuff. Time passes. More invasions, more recaptures, D, E, F, and G. H stands as it is for a while. That ridge provides some protection from the spring floods, and if you keep a sentry up there you can see the enemy coming for miles. Who wouldn’t want to park themselves in that real estate? The citizens of H leave behind cool totems eventually toppled by the people of I, whose lack of aesthetic sense if made up for by military acumen. J, K, L, adventures in thatched roofing, some guys with funny religions from the eastern plains, long-haired freaks from colder climes, the town is burned to the ground and rebuilt by still more fugitives. This is the march of history. And conquest and false hope. M falls to plague, N to natural disaster — same climatic tragedy as before, apparently it’s cyclical. Mineral wealth makes it happen for the O people, and the P people are renowned for their basket weaving. No one ever — ever — mentions Q. The dictator names the city after himself; his name starts with the letter R. When the socialists come to power they spend a lot of time painting over his face, which is everywhere. They don’t last. Nobody lasts because there’s always somebody else. They all thought they owned it because they named it and that was their undoing. They should have kept the place nameless. They should have been glad for their good fortune, and left it at that. X, Y, Z. "

Colson Whitehead , Apex Hides the Hurt