6.3. Manometric and volumetric respirometry
From the variety of manometric and volumetric methods of O2 consumption and CO2 production measurement (Lighton, 2008), Warburg manometry is the most important one. It is a closed-system constant-volume method, which means that the measured O2 concentration in the measurement vessel decreases in the course of an experiment. Therefore, air refreshment in regular intervals is necessary (Balderrama et al., 1992; Stabentheiner et al., 2003; Garedew et al., 2004). This limits experimental time. Air drying is usually done with silica gel. CO2 scrubbing can for example be done with caustic potash solution (KOH; see Lighton, 2008 for details). Moffatt and Núñez (1997) described a volumetric setup for the measurement of O2 consumption of honey bees foraging from artificial flowers.