Strong regularities in the size distribution of benthic communities have been observed in temperate lakes and streams. We tested if this regularity could be extended to the simplified communities of extreme polar habitats. We measured the biomass of algae, protozoans, and invertebrates colonizing ice-melt streams located in Edmonson Point (Victoria Land, Antarctica). These streams run only few weeks during polar summer. The benthic mats were dominated by cyanobacteria including small single cells, filamentous forms, and large Nostoc colonies. Chlorophytes and diatoms were intermingled in the mats that were colonized by protozoans, rotifers, tardigrades and nematodes. Typical benthic grazers (insect larvae and gastropods) were absent. Size spectra showed remarkably constant biomass in logarithmic size classes at all sites sampled. Comparison with temperate streams revealed that Antarctic communities reached similar biomass regardless of the harsh environment. However, distributions spanned over a much more limited size range than in temperate habitats because the largest organisms (Nostoc and tardigrades) were < 1µg. Regularity in size spectra, thought to be based on a strict coupling of size and trophic levels, was surprisingly confirmed in these antarctic communities despite the presence of large primary producers and the lack of large grazers.