Theoretical investigations suggest that nonconstant resource supplies play an important role in maintaining species diversity. However, for most organisms, explicit mechanisms enabling species coexistence due to resource variation are unknown. In the proposed study, the role of phosphorus (P) and light variations in maintaining species diversity in algal communities will be investigated, and the potential mechanisms of coexistence will be tested. Among these are the role of efficient resource storage and rapid induction of photosynthesis. After screening experiments with multispecies algal communities, six algal species that differ in their abilities to grow under several regimes of constant and fluctuating light and P supply will be chosen. Their kinetics of P- and light-dependent growth then will be determined. Next, a mathematical model will use these kinetics to predict the competitive dynamics over a wide range of light and P fluctuations. These predictions will be tested in numerous competition experiments. This combination of physiological and community experiments wit h mechanistic theory will allow the explicit testing of theory and of the role of non-equilibrium conditions in these communities. Thus, this will indicate the degree to which the knowledge of species physiology can be used to predict the dynamics and structure of competitive communities.
