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

Abstract

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 increasingly 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 conductivity. 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 to 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 conductivity were usually accompanied by decreases in Chl a concentration and a shift away from cyanophyte species in favor of chlorophytes, cryptophytes, and chrysophytes. This change in the importance of these phytoplankton phyla, which occurs at relatively low salinities (-3,500 PS cm-*), acts to limit phytoplankton biomass in these P-sufficient systems by restricting the growth of nitrogen-fixing species. Salinity-linked shortages of nutrients other than P may account for these changes,

Relative importance of iron and molybdenum in restricting phytoplankton biomass in high phosphorus saline lakes

“…Field Collection-Eleven lakes in east-central Alberta were selected based on their wide range of salinities (Bierhuizen and Prepas 1985;Marino et al 1990), their location within a relatively small geographical area (Evans and Prepas 1996), and accessibility. Eight of these lakes were sampled seven to eight times between early May and mid-September 1994.…”

“…Orthophosphate uptake rates were determined in Camp and Cooking on 15 August and in eight lakes from 19 to 2 1 July by a modification of the assay method of Lean and Rigler ( 1974) as described by Evans and Prepas ( 1996). Uptake experiments began within 30 min of sample collection and continued for 5-10 h at lakeside and in the laboratory.…”

“…Uptake experiments began within 30 min of sample collection and continued for 5-10 h at lakeside and in the laboratory. APA was measured from July to September by the method of Hill et al (1968) as modified by Pick (1987a) and Evans and Prepas (1996).…”

“…We examined water chemistry and phytoplankton communities in 11 saline lakes with high total phosphorus concentrations (up to 26,000 kg liter-'; Evans and Prepas 1996) to examine whether lake phytoplankton biomass is limited (restricted by low bioavailability of a given nutrient or nu-trients) by P because the P pool is biologically unavailable; low concentrations of inorganic N; low bioavailability of MO (a nutrient required for N, fixation); or low bioavailability of Fe.…”

Temporal and spatial features of the thermohydrodynamics of shallow salty lagoons in northern Chile

“…Boxlike (i.e., zero-D) approaches have been used to describe salty lagoons and to quantify changes in their ecological features due to changes in external forcing conditions, such as climate changes or modification of hydrological conditions (Evans and Prepas 1996;del Castillo and Farfá n 1997;Ló pez-Gonzá lez et al 1998). Timms (2005) described a theoretical model for ecological shifts in Australian salty lagoons due to changes in the salinity and nutrient input, showing that changes in nutrient inputs move the ecosystem between phytoplankton or macrophyte domination, whereas water salinity increases move the ecosystem from macrophyte domination toward microbial mat domination.…”