The photosynthetic light dispensation system: Application to microphytobenthic primary production measurements

Abstract

Measurements of microphytobenthos primary production were carried out in the German Wadden Sea in order to test the application of a 'Photosynthetic Light Dispensation System', which was originally developed for photosynthetic research of higher plants. A description of the computer-controlled system, consisting mainly of a subunit providing the irradiance (photosynthetically active radiation, PAR), and a subunit equipped with a Clark-type electrode for measuring oxygen production and respiration processes is given. The system allows rapid and reproducible measurements of photosynthesis-irradiance (P-E) curves at light modes predetermined by the computer and simple, rapid data analysis. Additionally, P-E curves obtained by this system were compared to those received by simultaneously conducted 14C measurements. Primary production measured by the oxygen method was on average 2.00 times higher than the values obtained by the 14C method. Production rates varied between 1.7 and 4.1 mg C mg chl a-1 h-1 with a mean of 2.75 mg C mg chl a-1 h-1.