The most of water bodies of freshwater lakes in Antarctica are considered to be nutrients limited. Our previous study on freshwater lakes in Antarctica, showed that the nutrient concentrations of the interstitial water in the benthic mat are either equaling or surpassing that of temperate eutrophic lakes.Then, it is considered that there are any mechanisms the nutrients hardly discharged from lakebeds to water column in Antarctica.

To reveal the mechanisms, we established two diffusion models to represent dynamics of silicate and phosphate in lake water and benthic mat on the vertical axis. The diffusion model combined with effect of mat viscosity and biological consumption was used to predict the distribution of nutrient concentration and was compared with observation data. In the silicate model, biological consumption can be excluded because there are few organisms using silicate in Antarctic lakes such as diatom. Then, we firstly estimated the effect of mat viscosity on the molecular diffusion using silicate model. Secondly, we estimated the biological consumption using phosphate model with estimated mat viscosity by silicate model. Our study by combination of theoretical and observational approach suggests that a mechanism of nutrients enclosure inside benthic mats in Antarctic oligotrophic lakes is caused by viscosity of the mats and uptake by phototrophs.