During summer, ice-free areas are common in Maritime Antarctica, and vegetation and microbial communities frequently occur in the moist parts of catchments. In this paper, we present new data and evaluate the biomass, C, N, and P content of various types of vegetation, and the water catchment of an oligotrophic lake sited at Byers Peninsula, Livingston Island, South Shetland Islands. As the main results show, the total amount of C, N, and P contained in the organisms of the watershed is 144, 0.71 and 0.018 g m-2, respectively. According to element contents, 98% of the biological C from the watershed is within mosses and microbial mats structures (79.1 and 19.0% respectively). Also, 98.7% of the N is partially distributed between moss carpets, microbial mats and lichens, 55.2, 43.5, and 3.37 x 10-7% respectively. On the other hand, 90.2% of P is within moss carpets structures. Nutrient pools in the communities of Limnopolar Lake itself are a minor component of the whole catchment.