Emergent vegetation was sampled in 15 oxbow lakes in a 50-km segment of the Athabasca River in northeastern Alberta. Cover of individual species was visually assessed in plots at the outer, middle, and (or) inner edge of the emergent zone of each lake ( n , 37 sample units). Detrended correspondence analysis showed two main axes of variation. The first axis related to salinity. Water conductivity ranged from 170to 12200 pS cm-' and community types ranged from freshwater fens to saline wetland communities dominated by Scolochloafestucacea, Scirpus maritirnus, and Triglochin maritima. The second axis of variation related to water-level fluctuations. Half of the lakes had an increase in water level in the recent past (ca. 6-30 years). In these lakes, Typha latifolia was dominant in both grounded and floating substrates subjected to increased water levels. Sedge communities dominated by Carex rostrata, C . aquatilis, and Acorus calanzus were common in sites with stable water levels. In freshwater lakes, floating substrates were established over open water by the lateral growth of floating stems of Calla pal~tstrisand Potentilla palustris. Floating substrates were not in the saline sites probably because these open-water colonizers were not present under saline regimes.