Initial results on the use of pH-stat titration (AIDA method) for the measurement of algal photosynthesis

The present work deals with the development of a method, named AIDA (algal inhibition detection analysis) for the measurement of algal photosynthesis by pH-stat titration. According to the pH probe signal, a titrator doses a saturated solution of CO2 to maintain the pH at a set-point value, buffering variations induced by photosynthetic CO2 consumption. The CO2 titration curve, after an initial lag Phase, is well interpolated by a straight line, whose slope is proportional to the photosynthetic CO2 uptake, until photosynthesis becomes limited probably due to nutrients limitation. Preliminary experimental results confirm that, under comparable test conditions, activity estimation was well repeatable. Moreover, the method could sense the photosynthetic response to nutritional changes (N:P ratio) and to the presence of toxicants. Therefore, AIDA shows potential applicability for both limnological studies and biomonitoring.