Our experimental units were treated as ‘batch cultures’ (as opposed to chemostats), whereby growth media was not replenished over the course of the experiment. The typical timeseries of algal growth in batch cultures involves logistic growth followed by a decline in algal biomass once nutrients are depleted (see Fig. S3 for growth curves of algae used in this experiment).
The decline phase makes fitting of traditional growth equations (e.g. Gompertz functions) to the time-series of batch cultures problematic at best, impossible at worst. Because of this, we decided to summarize the time-series of each batch culture using two easily interpretable metrics that give the maximum potential growth rate of a species GRmax (a proxy for r, the instantaneous per biomass rate of increase) and the maximum biomass Bmax achieved in culture