Species-specific phytoplankton growth rates via diel DNA synthesis cycles. I. Concept of the method

A conceptual basis is established to estimate the duration of cell cycle phases from a partially synchronized population. This information, together with the time course of cell cycle phase fractions, can be applied to estimate species-specific, in situ growth rates of phytoplankton. The model adopts the paired-nuclei method of McDuff & Chisholm (1982) with the substitution of the sum of S, G2, and M phases of the cell cycle as the terminal event. Quantitative fluorescence microscopy is used to measure unicellular DNA contents through a diel cycle. The model has the advantage of avoiding bottle incubations and allows the measurement of species-specific growth rates.