Ecological patterns of diatom assemblages from Mackenzie Delta lakes, Northwest Territories, Canada

Sediment samples were collected from 77 lakes in the Mackenzie Delta repres enting a gradient of lakes from those having continual connection with the sediment-laden Mackenzie River to lakes having connection for only a couple of days every few years. Diatom assemblages in all lakes were dominated by a diverse benthic microflora, primarily from the genera Navicula and Nitzs chia. Maximum relative abundance of the dominant taxon at all sites was les s than 30%, and most taxa did not dominate in more than one or two lakes. D elta lake assemblages were distinct from diatom assemblages associated with other regional transects of upland tundra and forest lakes. Detrended corr espondence analysis showed that nonmotile epiphytic genera, such as Coccone is and Gomphonema, were more common in lakes having a lower influence from the Mackenzie River, reflecting the extensive macrophyte growth within thes e lakes. Species diversity decreased as macrophyte production increased. Ta xa responses along this macrophyte production gradient were modeled using p artial least squares regression. Diatoms were sensitive to the degree of ri ver influence, and the related biological and limnological changes, suggest ing assemblages can provide an indication of hydrological variability withi n Mackenzie Delta lakes.