A modular system for the measurement of CO2 and O2 gas flux and photosynthetic electron transport in microalgae

Clinton A. Oakley, Brian M. Hopkinson, Gregory W. Schmidt

Limnol. Oceanogr. Methods 10:968-977 (2012) | DOI: 10.4319/lom.2012.10.968

ABSTRACT: Conventional means of assessing net photosynthetic rates of microalgae have largely relied upon the use of oxygen electrodes or carbon isotope radiolabeling. These methods are simple but inadequately resolve simultaneous fluxes of the gaseous substrates and products of photosynthesis, CO2, and O2. Fluorometric methods allow for assessment of the photosynthetic efficiency of excitation energy capture by the light-harvesting complexes and electron transport chain, but do not directly measure photosynthetic rates, because they do not resolve the fate of excitation energy downstream of electron transport chain. Here we describe and validate the accuracy of a compact system for the simultaneous, real-time, and comprehensive measurement of photosynthetic CO2 and O2 flux as well as photosynthetic electron transport in microalgae, from which net and gross rates of carbon fixation and oxygen evolution can be derived. Essential components include an infrared gas analyzer, gas-phase galvanic oxygen electrode, and pulse-amplitude modulated fluorometer.