Numerical modeling of the interaction between nutrient–phytoplankton–zooplankton–detritus system components during the spring thermal bar

In this paper, a nonhydrostatic 2.5D numerical model for simulating the hydrobiological processes during the spring riverine thermal bar in Kamloops Lake (British Columbia, Canada) is described. A thermal bar is a narrow zone in a lake where the water, which has a maximum density, sinks from the surface to the bottom. Numerical modeling of the dynamics of plankton ecosystems is implemented using the nutrient–phytoplankton–zooplankton–detritus model of Parker (1991). The hydrodynamic model, which takes into account an effect of the Coriolis force, is written in the Boussinesq approximation with the continuity, momentum, energy, and salinity equations. The data obtained in numerical experiments show a good agreement with that of Holland et al. (2003). Simulation results demonstrate that the maximum concentrations of phytoplankton are in the thermoactive (the inshore side of a thermal bar) region of the lake. Calculations under variable temperature conditions of the Thompson River show that the warm river waters facilitate a rapid growth of the phytoplankton and leads to a significant reduction of the nutrient in this area. However, these thermal boundary conditions have a little impact on the changes in zooplankton and detritus biomass.