ALKALINITY AS A USEFUL MEASURE IN BIOGEOCHEMICAL PROCESS STUDIES (EXAMPLES OF AEROBIC PHOTOSYNTHESIS AND ANAEROBIC MINERALIZATION OF ORGANIC-MATTER IN A TROPICAL LAGOON)

The usefulness of alkalinity measurements in biogeochemical process studies is emphasized by two examples concerning aerobic photosynthesis and anaerobic mineralization of organic matter in a tropical lagoon in the Ivory Coast. From changes in alkalinity it is possible to distinguish two photosynthetic periods in the epilimnion, one with a predominance of NO//3 assimilation, the other with a predominance of NH//4 assimilation. In the hypolimnion, during the stratification period, changes in alkalinity associated with changes in the metabolic products of mineralization (CO//2, NH//4, SH//2) permit one to demonstrate the complete mineralization of the organic matter into CO//2 and to estimate the quantities of pyrrhotite and pyrite produced due to SH//2 production by sulfate reduction.