Reducing activity and the formation of base in the coralline algae: an electrochemical model

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Abstract
SUMMARY AND CONCLUSIONS: In the process of calcification in the coralline algae, Clathromorphum and Corallina, the energy is derived from photosynthesis; the outer surface evolves carbon dioxide while calcium carbonate is deposited between the algal filaments. Evidence suggests that calcification may be brought about essentially by separation of acid and base followed by preferential removal of an acid component in the form of carbon dioxide.These algae show strong oxidase, catalase and carbonic anhydrase activity, consistent with the processes postulated. The calcified algal thallus is normally reducing. Platinum electrode potentials, Eh, measured on and immediately below the outer surface of fresh and healthy Clathromorphum crust following abrasion ranged from 50 to 100 mV, some 150–370 mV negative to that of the surrounding water at the time. These potentials in the alga were most reducing after the material had been exposed to strong sunlight. Eh potentials, measured by electrodes of platinum foil attached to the outer surface of Clathromorphum in such a way as to shield it from light and from gaseous exchange from the sea water, reached values between 113 and -182 mV, or up to 480 mV negative to the Eh of the surrounding sea water.Oxidation of crude suspensions of crushed fresh material showing reducing activity resulted in the production of base by removal of hydrogen ions. The amount of base so formed was greater when suspensions were first incubated out of contact with air for periods of up to several days, reducing conditions being enhanced by respiration of the alga alone or in conjunction with bacterial growth.

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