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How climate change alters ocean chemistry By studying icecores scientists wantto discover whichorganisms live in theice. Air bubbles inAntarctic ice coresalso provide clues tothe presence of tracegases in the formeratmosphere, and topast climate. The icecores are drilled usingpowerful tools. Formore detailed studythey are analysed inthe laboratory.When ice crystalsare observed undera special polarizedlight, their finestructure revealsshimmering colours.which depends on the animal group and lifestyle. In spiteof enhanced regulatory efforts by the organism to regulatethem, acid-base parameters undergo permanentadjustment within tissues and body fluids. This, in turn,can have an adverse effect on the growth rate or reproductivecapacity and, in the worst case, can even threatenthe survival of a species in its habitat.The pH value of body fluids affects biochemical reactionswithin an organism. All living organisms thereforestrive to maintain pH fluctuations within a tolerablerange. In order to compensate for an increase in aciditydue to CO 2, an organism has two possibilities: It musteither increase its expulsion of excessive protons or takeup additional buffering substances, such as bicarbonateions, which bind protons. For the necessary ion regulationprocesses, most marine animals employ speciallydeveloped epithelia that line body cavities, blood vessels,or the gills and intestine.The ion transport systems used to regulate acid-basebalance are not equally effective in all marine animalgroups. Marine organisms are apparently highly tolerantof CO 2when they can accumulate large amounts of bicarbonateions, which stabilize the pH value. These organismsare usually also able to very effectively excreteprotons. Mobile and active species such as fish, certaincrustaceans, and cephalopods – cuttlefish, for instance –are therefore especially CO 2-tolerant. The metabolicrates of these animals can strongly fluctuate and reach