Pingüinera Stream is one of the two main lotic environments of Cierva Point (Antarctic Specially Protected Area No. 134) on the Danco Coast, Antarctic Peninsula. It originates in a large snowfield, flows through a penguin rookery, moss and grass banks, discharging into Cierva Cove. During late Antarctic summer 2003, we sampled the stream at six locations along its course. Abiotic features characterize it as a clear water system, yet receiving a very high amount of PO4-P and NH4-N from the rookery. These nutrients decrease downstream mainly due to uptake by epilithic algae and oxidation of NH4+ to NO3-, consequently lowering pH and dissolved O2, which was always under-saturated. Strong correlations between all these parameters support these findings. The epilithic algal community shows both temporal and spatial changes in biomass, composition and relative frequencies. Dominant species at the higher reach of the stream are cyanobacteria, mainly Chamaesiphon subglobosus (Rostafinski) Lemm. and a mesh of Leptolyngbya spp. filaments. The chlorophyta Prasiola calophylla (Carmich.) Menegh. dominates the community in oxygenated, fast-flowing reaches. Comparison with the other main stream from Cierva Point, which is not influenced by the rookery, shows that growth and survival of the epilithic community in this area is limited by factors other than nutrient concentrations.