The stability of pH and dissolved inorganic carbon (DIC) in microalgal culture media

The use of culture media and sterile technique involving flaming of equipment in order to maintain unialgal or aseptic conditions is standard laboratory practice. However, as a result, atmospheric CO₂ concentrations, especially within laminar flow units but also in the laboratory as a whole, can become quite elevated. Media exposed in these conditions during routine work was observed to absorb this CO₂ and become increasingly acidic with time. This has consequences for long-term culture maintenance and eco-physiological studies. The degree of this effect will vary between laboratories, as well as over time as global ambient CO₂ concentrations continue to increase. Various ways of mitigating this are discussed.