An individual-based model for the analysis of Prochlorococcus diel cycle behavior

•We developed an individual-based model (IBM) for the Prochlorococcus diel cycle.•This model captures behavior specific to Prochlorococcus such as ultradian growth.•We evaluated the model using cell cycle data from North Atlantic populations.•Optimizing the model to DNA histogram data gives reliable estimates of growth rates.

Prochlorococcus spp. are the smallest and most numerous phytoplankton in the ocean. The tightly-phased diel dynamics of cellular growth and division can be used to estimate population growth and mortality rates of Prochlorococcus in the field. However, traditional approaches for making these estimates involve deconvolving cell cycle phases from DNA distributions, a potential source of error. In this study, we used an individual-based model (IBM) to capture the cell size patterns, DNA content, and cell cycle phase distributions of Prochlorococcus. Model parameters were estimated from cell cycle data of field populations in the North Atlantic Ocean and then optimized using the Nelder-Mead algorithm. The model reproduced observed field diel growth and cell cycle dynamics well. Model optimization can be used to estimate population growth rates and other cell cycle parameters directly from DNA distributions, independent of cell cycle phase deconvolution.