DISTRIBUTION OF STREAM MACROALGAE IN 4 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 stream s included small snowmelt tributaries, those flowing through wetlands, pond outflows, glacial meltwaters, and large trunk rivers, some of wh ich had become braided in their lower portions. Larger channels tended to be quite turbid, and macroscopic algae were negligible in these re aches because they lack adequate light and hard substrata for attachme nt. The overall stream macroalgal flora was relatively small (15 speci es) compared to that of other regions of the North American tundra. Cy anobacteria and Chlorophyta accounted for all but one species. The mos t 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 st ream reach ranged from 0 to 5, with a mean of 1.3. The amount of strea m 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.