Methods for Measuring Algal Carbon Fixation in Flow-Through Seawater

Abstract

Benthic algae and animals are generally in stirred or flowing seawater due to water currents and waves. It is hard to measure their photosynthetic or respiratory rates in a small closed container due to their large size and bottle effects. Seawater flow-through method can avoid bottle effects and be applied to large size organisms or benthic communities. By measuring the concentrations of dissolved oxygen or other parameters in the inlet and outlet of the tube simultaneously, one can calculate photosynthetic or respiratory rates using flow rate and biomass used and the difference in O₂ concentration between the inlet and outlet. This method can eliminate the effects of diffusion boundary layer surrounding the organisms, and overcome the bottle effects that lead to increasing accumulation of O₂ and decreasing availability of CO₂ and nutrients for marine plants. It can also be applied to measurements of respiration of animals and biological calcification.