>      Report in todays paper says that about 50% of the CO2 in the atmosphere ends up in the oceans. It says this may affect the shells of sea critters. How will this happen? How does it happen?<

CO2 dissolves in water, producing a mix of H2O and CO2.  These can react to form H2CO3, aka carbonic acid, a very unstable substance, but as an acid, it can be a nuisance for shells.  H2CO3 can separate into H+ (hydrogen ions) and HCO3- (bicarbonate ions), in addition to going back to CO2 plus H2O.  HCO3- can form H+ and CO3-- (carbonate ions).  Thus, H2O, CO2, H2CO3, H+, HCO3-, and CO3-- are in a balance.  Molluscan shells are CaCO3; adding too much H+ (i.e., acid) causes them to dissolve.  More CO2 in the system adjusts the concentration of all the others.  However, there is so much CO3-- and HCO3- in the oceans that the balance is relatively stable (a buffered system, if you remember that part of chemistry class).

A complicating factor is that algae use up CO2 in photosynthesis.

> Is there a time line for panic? Has it happened before?<

The amount of CO2 has varied a lot over time.  The main ecological problem with the current changes such as global warming and increasing CO2 is that it is happening very rapidly, from a geological perspective.  Anything that is currently living near the edge of its tolerance might have trouble adjusting fast enough or coping as things change.

    Dr. David Campbell
    Old Seashells
    University of Alabama
    Biodiversity & Systematics
    Dept. Biological Sciences
    Box 870345
    Tuscaloosa, AL  35487-0345 USA
    [log in to unmask]

That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa

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