Incorporation of the intracellular elemental correlation pattern into simulation models of phytoplankton uptake and population dynamics

Compelling evidence of complex statistical relationships among various elements contained within phytoplankton cells has traditionally been ignored in models of algal nutrient uptake and population dynamics. Here we present a new approach, incorporating a phytoplankton intracellular elemental correlation pattern into the existing dynamic simulation model of a freshwater lake. Within this approach, uptake and cycling of elements that are likely to become limiting during the simulation period are described by ordinary differential equations. Dynamics of nutrients that are unlikely to become limiting are described either by differential equations or, when more practicable, by multiple regressions on environmental variables and cell quotas of other elements. This allows an easy simultaneous consideration of a wide range of elements. The model adopting the described approach was tested on a data set for Rostherne Mere, Cheshire, UK. It showed a good fit between observations and simulations for all considered variables, including the population dynamics of Ceratium hirundinella and Microcystis aeruginosa, the outcome of interspecific competition and changes in concentrations within algal cells and in the surrounding lake water. The approach could easily be implemented in models of bioreactors, chemostat experiments and aquatic ecosystems.