Taxonomic and ecological investigations of algae on steam-warmed soil on Mt Erebus, Ross Island, Antarctica

Abstract

Micro-algae and protonematal moss grow on steam-warmed, fumarolic ground at approximately 3500 m altitude on the active volcano Mt Erebus. Outside fumarolic areas there is no vegetation. Soil surface temperatures are up to 60°C and moisture is supplied by condensation of steam. The air temperature in summer is generally between −20 and −30°C. The algal flora comprises four species of Cyanobacteria and 11 species and two varieties of Chlorophyta. Three Cyanobacteria, Mastigocladus laminosus, Phormidium fragile and an unidentified species of Lyngbya, grow well at temperatures above 30°C both in the laboratory and in the field. The last of these shows the strongest thermophilic response, having good growth at 50°C in culture and at up to 59°C in the field. The Chlorophyta are all unicellular members of the Chlorococcales with a dominant component of Chlorella taxa. These are typical mesophiles. In culture good growth is obtained at 22°C and in the field they are rarely observed above 30°C. Zonation in the visual appearance of vegetation and in the species composition occurs along the strong temperature gradients where soil surface temperature decreases with increasing distance from the hot steam emissions. The unique structure of this community within Antarctica and its possible airborne origin are discussed.