ORIGINAL PAPER

Abstract The cylindrical meltholes present in the abla-tion zones of many glaciers (termed cryoconite holes) contain complex microbial communities. A canonical correspondence analysis (CCA) of community structure and environmental gradients for cryoconite holes on two glaciers was undertaken. The Canada Glacier (7737¢S, 16255¢E) is located in the McMurdo Dry Valleys of Antarctica. The White Glacier (7927¢N, 9040¢W) is located on Axel Heiberg Island, Nunavut Territory, Canada. These glaciers are at similar, yet antipodal latitudes, are roughly the same size and en-dure approximately the same mean annual tempera-ture. The Canada Glacier cryoconite communities were found to be significantly (P=0.001) associated with six environmental variables, which together explained 55% of the biological variation. The White Glacier cryoco-nite communities were not significantly associated with environmental variables. The differences in CCA results were attributed to the relative amount of disturbance and isolation between each glaciers cryoconite holes. Canada Glacier cryoconite holes were mostly ice-cov-ered and undisturbed by meltwater flow, whereas high meltwater production and open cryoconite holes on the White Glacier may continually reset the community structure and habitat variability due to inter-hole mixing