Photosynthesis and the dynamics of oxygen consumption in a microbial mat as calculated from transient oxygen microprofiles

A new method is presented to determine the rates of oxygen consumption, net oxygen metabolism (defined as photosynthesis minus oxygen consumption), an d gross photosynthesis at high vertical resolution in benthic phototrophic communities. The rates of oxygen consumption and of net oxygen metabolism a s a function of depth and time are calculated from the dynamics in oxygen c oncentration, as measured with oxygen microsensors during light-dark cycles , by numerically solving the general non-steady state diffusion-reaction eq uation. The results, as obtained for a temperate intertidal microbial mat, strongly suggest that the vertical distribution and the dynamics in oxygen consumption are controlled by the supply of both oxygen and oxidizable subs trates from different sources. The depth distribution of gross photosynthes is, as obtained by the cycling procedure, showed reasonable agreement with the photosynthesis profile, as measured with the conventional light-dark sh ift method prior to the light-dark cycling experiment, thus supporting the applicability of the method.