Wolkowicz Gail S K, Yuan Yuan
Department of Mathematics and Statistics, McMaster University, Hamilton, ON, L8S 4K1, Canada.
Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada.
J Math Biol. 2016 May;72(6):1663-92. doi: 10.1007/s00285-015-0924-x. Epub 2015 Aug 28.
We discuss a mathematical model of growth of two types of phytoplankton, non-nitrogen-fixing and nitrogen-fixing, that both require light in order to grow. We use general functional responses to represent the inhibitory effect their biomass has on the exposure to light. We give conditions for the existence and local stability of all of the possible steady-states (die out, single species survival, and coexistence). We derive conditions for global stability of the die out and single-species steady-states and for persistence of both species when the coexistence steady-state exists. Numerical investigation illustrates the qualitative dynamics demonstrating that even under constant environmental conditions, both stable intrinsic oscillatory behavior and a period doubling route to chaotic dynamics are possible. We also show that competitor-mediated coexistence can occur due to the positive feedback resulting from recycling by the nitrogen-fixing phytoplankton. To show the impact of seasonal change in water depth, we also allow the water depth to vary in an annual cycle and discuss echo blooms in this context.
