Behavior of mixed Chlorophyceae cultures under prolonged dark exposure. Respiration rate modeling

The behavior of three different microalgal cultures, when exposed for a long period (>48 h) to dark conditions, was studied with a methodology based on respirometry. The cultures were transferred to darkness and the oxygen evolution in the reactors was monitored after successive air injections. Several sequential oxygen uptake rates were thus calculated and a respiration constant, assuming a first order decay of a fraction of the biomass, was obtained by calibration. Initial specific oxygen uptake rates were in the range of 0.9-5.1 mg O2 g TSS−1 h−1 and dark respiration constants in the range of 0.005-0.018 h−1.