Integral growth of submersed macrophytes in varying light regimes

The coverage, density, and species diversity of macrophytes in the shallow portion of lakes have important effects on water quality, ecosystem health, and sediment deposition, and are important factors in lake use for fishing, boating, swimming, and as waterfowl habitat. This significance and the complex requirements for macrophyte growth have stimulated the development of growth models to predict macrophyte biomass, oxygen production, nutrient cycling, etc. However, there is a lack of relationships that characterize the response of macrophyte growth to varying physical conditions. The growth model developed in this study relates the rate of production of rooted aquatic macrophytes to basic physiological parameters (growth and respiration rates) and controlling physical parameters (incident irradiance, water temperature, light attenuation by water and phytoplankton). The model is developed to be general, rather than specific to a particular plant species, with the intention of broadly characterizing macrophyte growth behavior as a function of a few key parameters. The growth equations are solved analytically using the assumption of uniform temperature and biomass over depth. Expressions for instantaneous rate of growth, daily production, and equilibrium biomass are found. A set of dimensionless parameters are defined and used to characterize four growth regimes. Model results are given in terms of the governing dimensionless parameters and then related to real world, dimensional parameters.