Figure 7.

The effect of urea input on dinoflagellate populations growing on nitrate. Nitrogen-limited dinoflagellate populations growing on nitrate under steady-state conditions (left panels) start to consume urea and proliferate following the input of extra nitrogen in the form of urea (right panels). Green color shows the nitrate uptake, magenta—the urea uptake. The intensity of a shade reflects the uptake rate (light shades—lower uptake rates, dark shades—higher uptake rates). In a putative homogeneous population (A) all cells express a similar mode of nutrition with the urea uptake prevailing over the nitrate uptake and follow the same dynamics. In a heterogeneous population (B), different cells express different modes of nutrition, thus forming several functional groups (sub-populations), each characterized by its own dynamics. Bulk uptake rates of nutrients might be the same in case of both homo- and heterogeneous populations at a given time, but further population dynamics can differ due to specific dynamics of each functional group within a heterogeneous population, which leads to various environmental impacts. In an utmost case, the dynamics of a heterogeneous population is defined by growth and proliferation of every individual cell, which can be described by individual-based modeling.