Landscape variables influencing nutrients and phytoplankton communities inBoreal Plain lakes of northern Alberta: a comparison of wetland- and upland-dominated catchments

A review of headwater lakes in undisturbed watersheds on the Boreal Plain, with indirect gradient analyses of chemical data, indicated a clear separat ion between those in wetland-dominated watersheds (57-100% wetland with var iable proportions of bog, fen, swamp, and marsh cover) and those in upland- dominated watersheds (0-44% wetland cover). In the former, percentage wetla nd cover in the watershed was positively correlated with total phosphorus ( TP, r(2) = 0.78, primarily bog), total nitrogen (TN, r(2) = 0.50), and diss olved organic carbon (DOC, r(2) = 0.74) concentrations. Rich fens appeared to sequester both TP and TN. In upland-dominated lakes, the ratio of catchm ent area to lake volume (CA/LV) was the strongest watershed correlate of TP concentration (r(2) = 0.56), whereas most limnetic nitrogen and DOC were g enerated in situ. Colour concentration, being highest in wetland lakes, was correlated with the ratio of isotopically defined effective drainage basin area to lake volume (eDBA/LV, r(2) = 0.63). Drainage basin slope was only weakly associated with water quality, likely because of low topographic rel ief (less than or equal to 11%). Higher Chlorophyta and Peridineae biomasse s in wetland-dominated systems than in upland-dominated ones may coincide w ith greater NH4+ availability.