Hydrological Processes, 2001, 15, 3447-3459

The altitudinal distribution of snow algae on an Alaska glacier (Gulkana Glacier in the Alaska Range)

Nozomu Takeuchi

Frontier Observational Research System for Global Change, International Arctic Research Center, University of Alaska Fairbanks, 930 Koyukuk Dr. P.O.Box 757335 Fairbanks AK 99775-7335 U.S.A.

Abstract

The altitudinal distribution of a snow algal community was investigated on an Alaska glacier (Gulkana Glacier in the Alaska Range) from 1270 m to 1770 m a.s.l.. Seven species of snow and ice algae (Chlorophyta and cyanobacteria) were observed on the glacier surface. These species were Chlamydomonas (Cd.) nivalis, Mesotaenium (M.) bregrenii, Ancylonema (A.) nordenskioldii, Cylindrocystis (Cyl.) brébissonii, Raphidonema sp., and two Oscillatoriaceae cyanobacteria. The altitudinal distribution of snow algae was different among the species: Cd. nivalis was distributed on the middle to upper area, M. bregrenii, A. nordenskioldii, and one Oscillatoriaceae cyanobacterium on the middle to lower area, Raphidonema sp. on the middle area, and Cyl. brébissonii and one Oscillatoriaceae cyanobacterium on the lower area. The total cell concentration and cell volume biomass of the snow algae ranged from 4.4 x 103 to 9.9 x 105 cells ml-1 and from 33 to 2211 µl m-2, respectively. The cell volume biomass changed with altitude; the biomass increased with altitude below 1600 m a.s.l., and decreased above 1600 m a.s.l. The community structure showed that A. nordenskioldii dominated on the lower part of the glacier, and that Cd. nivalis dominated on the upper part. The species diversity was relatively high at the lowest and middle site. The pH was 4.7 to 5.3 for snow and 4.9 to 5.7 for ice on the glacier. The altitudinal distribution of snow algae is discussed in terms of the physical and chemical condition of the glacier surface, and is compared with that on a Himalayan glacier. Larger biomass in the snow area on the Alaska glacier than that of the Himalayan glacier is likely due to less frequent snow cover in summer in Alaska. Small amounts of filamentous cyanobacteria on the Alaska glacier may allow washouts of unicellular green algae by running melt water and may cause a different pattern of altitudinal distribution of algal biomass on the ice area from the Himalayan glacier.
Keyword: snow algae, ice algae, Alaska, glacier, community structure