Potential effects of climate change on ion chemistry and phytoplankton communities in prairie saline lakes

Shallow, closed-basin saline lakes found in semiarid areas of Canada tend to be sensitive to changes in precipitation: evaporation ratios. Historical climatic information indicates that the area is becoming increas-ingly arid and this trend is expected to continue under current climate-change scenarios. The water chemistries and phytoplankton of six Alberta saline (> 1 g liter- ’ total dissolved solids) lakes were studied over a 12-yr arid period to evaluate potential chemical and biological effects of climate-induced increases in brine con-ductivity. Major ion concentrations, relative proportions of major ions, chlorophyll a concentrations, and the relative importance of different phytoplankton phyla were evaluated with respect to the increasing conductivity profiles of the lakes and with respect o the range of conductivities represented in the lake series. When the data were combined, concentrations of Na+, K+, Mg 2+, SOd2-, Cl-, and alkalinity were positively correlated with conductivity and Ca2+ was negatively correlated with conductivity. The relative proportions of Na+, SOd2-, and Cl- increased significantly with brine conductivity (2,900-30,900 @), and the proportions of other ions decreased. The variability of these relationships suggests that the brine compositions in some of these lakes are strongly influenced by local surface water and groundwater chemistry. Increases in con-ductivity were usually accompanied by decreases in Chl a concentration and a shift away from cyanophyt