Determination of microphytobenthos PSII quantum efficiency and photosynthetic activity by means of variable chlorophyll fluorescence

Abstract

A pulse amplitude modulated fluorometer (PAM) was used to investigate photosynthetic activity of m~crophytobenthos on an Intertidal mudflat Spectral ~rradiance measurements Indicate that 7500 of the signal detectable by the PAM onginates In the upper 150 pm of the s e d ~m e n t From the photosynthetic electron transport rate (ETR) measurements, it was concluded that the PAM could be used to observe changes in photosynthetic parameters during the day or the season Photoacclimation to lower irrad~ance was ind~cated by changes in the maximum ETR and the saturating photon irradiance parameter I, When cores were exposed to a high photon irradiance for several hours, vertical migration could be followed using reflectance spectra The data also showed that the benthic algae did not seem to expenence photoinhib~tion or COZ limitation To explain this, ~t is hypothes~sed that there is a continuous vertical migration in the top layer of the s e d ~m e n t , whele algae can a v o ~d photoinhibition due to prolonged periods of high irrad~ance and lack of CO2 by m~grating downwards whlle others migrate upwards