[CobaltBlue]

There are no dumb questions, only the questions you didn't ask, right? So, please forgive my ignorance - when the writers talk about "buffering", does this mean that they are talking about pH?

Casting my memory far, far back - calcium carbonate is a base, and I thought that the CO2 was acidic, so why wouldn't they combine?

Also, where did the calcium come from?

[VadeRetro]

... when the writers talk about "buffering", does this mean that they are talking about pH?

Not when they're talking about "buffering." If they start talking about potty-brains, yes.

BTW, I think calcium carbonate is a neutral salt. It probably won't do much to react with carbon dioxide because it essentially already contains a C0₂ molecule and precipitates out of solution as soon as it is formed.

[Physicist]

I think they mean that the CO2 content is buffered. Calcium carbonate releases CO2 when it dissolves, so if the CO2 pressure in the ocean is lower than the partial pressure of CO2 in the atmosphere, the dissolving shells will just bring it up again.

I remember reading that the CO2 content in the deep ocean is so low that a shell dropped into the ocean will dissolve before it reaches the bottom. I don't know whether that's correct.

As for the calcium, I suppose it's just there in solution in sufficient quantity.

[Ichneumon]

There are no dumb questions, only the questions you didn't ask, right?

Well, that depends. Consider Barbara Walters' interview question to Katherine Hepburn: "If you were a tree, what kind would you be?"

So, please forgive my ignorance - when the writers talk about "buffering", does this mean that they are talking about pH?

Hard to tell from the brief article above. pH buffering is one of the most common kinds of buffering, but any process (chemical or otherwise) which limits or softens the effects of something is properly called a buffer, so the paper may have been talking about something other than pH buffering.

Even in computers, message or data storage areas which temporarily store information as it's being passed from one place to another are called buffers, because they prevent data overruns from occurring if the incoming data momentarily arrives faster than it can be accepted by the destination. The memory buffer gives the data a safe place to pile up in a "traffic jam" until the "road" ahead opens up.

[Doctor Stochastic]

Buffering means having a repository of the item being buffered. So while the carbon dioxide levels swing wildly in the atmosphere, the plankton absorb excess to keep the active amount in the atmosphere more nearly steady. It's the same idea of a buffer in an acidic solution. Or a buffer in a computer I/O system. (Not the same as a buffer to polish a car.)

Calcium just exists in the crust. (Ultimate it was produced in a nova or supernova.) Calcium is very active and comines with acids such as carbonic acid to produce limestone (and marble.)