Modeling plankton seasonal succession

Background/Question/Methods: Each year, the plankton communities of temperate lakes receive a major perturbation: winter. The cold temperatures and low light levels due to deep mixing or snow-covered ice reset the communities, clearing the way for a cavalcade of species blooms and replacements called seasonal succession. This topic has occupied plankton ecologists for decades, culminating in a verbal model called the PEG-model, which describes seasonal succession in 24 steps. While the PEG-model summarizes extensive empirical understanding of what drives seasonal succession, as a purely verbal model, it is unable to make quantitative predictions on how successional trajectories might depend on environmental parameters. To address this issue, we are developing novel mathematical techniques for modeling plankton seasonal succession. Results/Conclusions: We have found that the seasonal forcing of plankton food webs can explain common successional patterns, such as a spring phytoplankton bloom, followed by a clear-water phase due to grazers, followed by summer dominance of inedible phytoplankton. It can also suggest other less intuitive dynamics, such as a spring bloom of inedible phytoplankton or year-to-year variability even under identical abiotic conditions. This approach lets us predict how successional trajectories differ between lakes and will respond to human-induced changes in environmental parameters.