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), and gross photosynthesis at high vertical resolution in benthic phototrophic communities. The rates of oxygen consumption and of net oxygen metabolism as a function of depth and time are calculated from the dynamics in oxygen concentration, as measured with oxygen microsensors during light-dark cycles, by numerically solving the general non-steady state diffusion-reaction equation. 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 substrates from different sources. The depth distribution of gross photosynthesis, as obtained by the cycling procedure, showed reasonable agreement with the photosynthesis profile, as measured with the conventional light-dark shift method prior to the light-dark cycling experiment, thus supporting the applicability of the method.