A model of the development of a periphyton community: resource and flow dynamics

An ecological model of periphyton dynamics was designed to approach the development of a periphyton community under the effects of surrounding nutrient concentration and light intensity. The model simulated the vertical heterogeneities of biomass, light irradiance, and nutrients within the periphyton mat. To determine the competition for resources between species, a Monod-type relationship was used to relate external nutrient concentration to periphyton uptake rate, and ‘Liebigʹs law of the minimum’ was used to combine light and nutrient effects on growth rate and tension strength of the algal cell. The effect of the periphyton community to the vertical distribution of water velocity was also numerically investigated. To confirm the validities, the developed model was verified using several cases: the external concentration was constant or was varied with different diffusion coefficients. Reasonable responses of the periphyton community to the ambience nutrient concentrations, light intensity and, in turn, temporal variation of nutrients during the development of a periphyton community strongly encouraged further application of the model. Variation in the water velocity in a vertical direction intensively contributed to the results of the model.