EXOTIC SPOROMORPHA AS INDICATORS OF POTENTIAL IMMIGRANT COLONISTS IN ANTARCTICA

A brief account is given documenting the development of aerobiological research in the Antarctic. The results of the British Antarctic Survey's contribution to an international programme on long-distance dispersal of aeroplankton over the Southern Ocean are presented. This was achieved by collecting airspora deposited in Tauber traps and in surface snow at sites on South Georgia (sub-Antarctic) and Signy Island (maritime Antarctic). Although only a small number of the samples were analysed, the results provided ample evidence of a continuous immigration of exotic sporomorpha of southern South American provenance. The cause of this rain of biological material is attributed to the not infrequent easterly tracking storm events generated over the south-east Pacific Ocean. As they gain momentum over southern South America they become seeded with pollen and spores, and possibly by larger organelles such as invertebrates and seeds. These high winds may be deflected southwards by a blocking anticyclone over the South Atlantic Ocean, allowing a proportion of the sporomorpha to be deposited over land far to the south. The occurrence of such exotic sporomorpha in these remote and environmentally hostile regions is used here as evidence to support the hypothesis that there is a continuous input into the Antarctic biome of viable propagules from more northerly landmasses. While no exotic bryophyte or lichen spores have yet been detected in trapping experiments, the extremely rare occurrence of certain bryophytes associated only with geothermal sites in the Antarctic and in laboratory-cultured soils from barren ice-free terrain indicates that a pool of viable but dormant propagules is probably widespread in Antarctic soils and ice. However, germination and development in situ are possible only under exceptional environmental circumstances. An international programme is being planned to detect the main trajectories of long-distance transport of propagules into the Antarctic and to test their viability.