Modern Stromatolites in Antarctic Dry Valley Lakes

We report here the discovery of the first modern (Holocene) bluegreen algal stromatolites from Antarctica. Several types occur within these permanently ice-covered, dimly lit, nonturbulent, seasonally glacier-fed lakes, where the habitats vary chemically from fresh-to-saline and anoxic to oxygen-supersaturated. The dominant blue-green alga and principal stromatolite builder in all types is the oscillatoriaceous species, Phormidium frigidum, which can grow under the wide range of microhabitat conditions occurring in these Antarctic lakes and in the absence of competitive exclusion by eukaryotes, or significant browsing or burrowing by Metazoa. Precipitation of calcite and binding or trapping of sediments give the bluegreen algal mats internal laminae, preserving them as stromatolites. We suggest these frigid Antarctic lake stromatolites may be analogs of those that once inhabited deepwater Precambrian ecosystems.