Distribution of Stream Macroalgae in Four High Arctic Drainage Basins

Eighty-three stream reaches were sampled from four drainage basins in the central portions of Axel Heiberg and Ellesmere Islands. The streams included small snowmelt tributaries, those flowing through wetlands, pond outflows, glacial meltwaters, and large trunk rivers, some of which had become braided in their lower portions. Larger channels tended to be quite turbid, and macroscopic algae were negligible in these reaches because they lack adequate light and hard substrata for attachment. The overall stream macroalgal flora was relatively small (15 species) compared to that of other regions of the North American tundra. Cyanobacteria and Chlorophyta accounted for all but one species. The most widespread species was the colonial cyanobacterium, Nostoc commune. Only Scytonema mirabile (Cyanophyta) was a new addition to the stream macroalgal flora of arctic North America. The number of species per stream reach ranged from 0 to 5, with a mean of 1.3. The amount of stream bottom covered by macroalgae was 0 to 75%, with an average of ca. 5%. Both species number and percent cover per reach are relatively low.