A mathematical model was developed to simulate the dynamics of the benthic algal mat community existing in Lake Bonney, south Victoria Land, Antarctica. The model consists of three differential equations, explaining the interactions of the mat system with the two nutrient systems included in the model. The two nutrient types involved are a limiting inorganic nutrient and an organic nutrient, i.e. an algal mat produced extracellular product. The model results in an algal mat whose biomass shows an annual net increase under favorable conditions.