Characterizing and quantifying photoinhibition in intertidal microphytobenthos

This study characterizes the short-term influence of the sustained saturating irradiance encountered by the microphytobenthos inhabiting intertidal mudflats. The kinetics of photoinhibition in epipelic microalgae from intertidal mudflats were investigated in the laboratory. Previously isolated benthic microalgae were exposed to a saturating photon flux density (PFD) for periods ranging from 0 to 180 min; every 30 min, a photosynthesis-irradiance curve was established to quantify the effect of the alpha(B) saturating PFD on both parameters alpha(B), the photosynthetic efficiency, and P-m(B), the photosynthetic capacity. The decreased from the beginning of light exposure until the end, whereas P-m(B) first slightly increased and then diminished from 90 min exposure onward. It turned out that epipelic microphytobenthos undergoes photoinhibition after about 90 min of saturating PFD. The possible ecological consequences of these ecophysiological results are discussed.