A METHOD TO IMPROVE THE SPATIAL-RESOLUTION OF PHOTOSYNTHETIC RATES OBTAINED BY OXYGEN MICROSENSORS

To determine gross photosynthesis in benthic microalgal communities, o xygen microelectrodes were used to measure the rate of decrease within the first 4 s after extinction of light. Photosynthetic rates calcula ted from third-order polynomial fits to the curve of decreasing O-2 co ncentration were compared to the rates obtained by the traditional met hod, where rates were estimated from linear regression. When photosynt hesis was calculated for the fitted initial rates of O-2 decrease, max imum rates in microbial mats were up to 32% higher, and the depth-inte grated gross photosynthesis was 5%-10% higher than the rates determine d by the traditional method. The determinations from fitted initial ra tes also resulted in a more detailed profile of phytosynthetic rate th an that normally obtained. Computer simulation based on diffusion mode ls, where the estimated initial rates of O-2 decrease were assumed to represent actual photosynthesis rates, verified the validity of the cu rve-fitting procedure for obtaining high-resolution photosynthesis pro files.