Encystment of a cold-water dinoflagellate - From in vitro to in silico

Blooms of dinoflagellates are frequently observed in coastal regions. The dynamics of these blooms are strongly affected by life cycle transitions. For example, many species form resting cysts at the end of the growth period that act as a seed population. Despite considerable efforts, one major process of the dinoflagellate life cycle - the encystment - is not fully understood. In this study, we reanalyse a published laboratory data set for the cold-water dinoflagellate Biecheleria baltica and develop a numerical model to study cyst formation. We find significant differences between cell counts and biomass, leading to different conclusions about the encystment process. To accurately reproduce the laboratory data, two mechanisms have to be taken into account in the model: a time lag in cyst formation and a reduction in the growth rate of vegetative cells as soon as cysts are formed. Using this model we are able to identify and formalise the functional dependence among growth, cyst formation, and environmental factors. Our model can serve as a prerequisite for dinoflagellate life cycle models to study the dynamics of bloom formations.

► Reanalysis of a published data set on dinoflagellate encystment show differences in biomass and cell counts. ► Development of an encystment model based on biomass. ► Good agreement between observed and simulated nutrient, motile cell and cyst concentrations. ► Time lag in cyst formation and reduction of growth rate of vegetative cells as soon as cysts are formed. ► Overlapping temperature ranges for growth and sex.