What this work is about, in plain words
The density of an algae culture can be measured in different ways: by weighing, by turbidity, chemically or by counting cells. The authors related these methods to each other using the diatom Cylindrotheca closterium.
Culture density — how many cells or how much biomass it contains — is a key parameter of almost any experiment with microalgae. It is measured by different methods: by optical density, by weighing dry mass, by the oxidizability of the biomass, or by counting cells directly under a microscope. The results come in different units, which makes it hard to compare studies. Bottom-dwelling diatoms are doubly difficult: their heavy cells settle quickly, and it is hard to take a sample correctly. The authors set out to relate the methods to each other.
The experiments were carried out on the diatom Cylindrotheca closterium, grown in the laboratory in batches and in continuous-flow mode. The density of each sample was measured by all four methods.
According to the authors, coefficients were found for converting the results of one method into the units of another. For each method, its advantages, drawbacks and limits of applicability are described.
The work is useful for anyone growing diatoms: it makes it possible to compare one's own measurements with published data and to choose a method for the task.
Limitations. The coefficients were obtained for one species under laboratory conditions. For other species and conditions, they need to be determined anew.