Factors affecting the introduction and distribution of fungi in Vestfold Hills, Antarctica
The impact of human disturbance on fungal flora around Davis Station and the Vestfold Hills in Antarctica (68 0 35'S 77" 58'E) was examined by monitoring air spora and soil fungi over a 12 month period in 2001. A number of fixed sample points were established around Davis Station from which soil was collected on a monthly basis as conditions allowed. Additionally, two transects were set up. The first transect ran 3km through the station from north to south extending from 50m beyond the limit of the station buildings, to the south of Heidemann Bay. The second transect extended 18km west to east along the length of the Ellis Fjord and Lake Druzhby as far as Trajer Ridge, 5km from the polar plateau. Each transect comprised 5 sites which were sampled on a fortnightly basis throughout 2001 using rotorod airborne particle samplers and soil dilution plates. Numbers of airborne particles were determined by counting under a light microscope. Fungi were isolated from soil using full strength potato dextrose and Czapek Dox agars as well as hair bait. Fungal isolates were identified on the basis of their general morphology and also by genetic analysis of ribosomal Intemal Transcribed Spacer regions. Fungal populations were sparse at all locations with the exception of the living quarters where numbers were consistently high. Furthermore, although seasonal variations were observed at many of the sites, no such variation was recorded at the station which would indicate a continuing source of inocula or less harsh conditions. Increased fungal numbers near to living quarters was also observed at other stations (Law Base, Australian, Progress II, Russian and Zhong Shan, Chinese) but not beyond their confines. Also, there was little species overlap between fungi found close to station living quarters and those found farther afield, which would indicate that whilst there was a clear human impact, the fungi associated with these areas do not appear to be becoming established elsewhere. Study of the optimum growth temperatures of fungi isolated from both soil and air showed that all isolates were psychrotrophs (i.e. were able to tolerate temperatures below 5°C) and 39% of them were psychrophiles (i.e. their optimum growth temperature was 15°C or below and they were able to grow at O°C). All genera were capable of surviving periods of at least 28 days of desiccation.