Inhibiting diatom motility: a new tool for the study of the photophysiology of intertidal microphytobenthic biofilms

The study of the photophysiology of intertidal microphytobenthos biofilms has been hampered by the confounding effects of vertical migration by motile microalgae. The present work introduces a methodology to obtain undisturbed nonmigratory biofilms, based on the diatom motility inhibitor latrunculin A (Lat A). Application of Lat A to intact sediments prevented light-induced vertical migration while not affecting the biofilm photosynthetic activity or disrupting the photic zone microenvironment. The inhibition of microalgal migration maintained the surface microalgae biomass despite exposure to stimuli that induced large migratory responses in noninhibited samples, including supersaturating irradiances or darkness. The characterization of the photophysiological responses of undisturbed biofilms without the interference of changes in surface biomass was illustrated by addressing two questions that are not possible to study on migratory biofilms with the existing methods: (i) the construction of light-response curves of steady-state photosynthetic activity, commonly used to characterize the photoacclimation status of photoautotrophs, and (ii) the characterization of the induction and relaxation kinetics of nonphotochemical quenching of in vivo fluorescence, required for the study of photoprotective processes or photoinhibition.