Climate warming and the onset of salinization: Rapid changes in the limnology of two northern plains lakes

摘要

Water resources of the interior plains region of North America may be adversely affected by climate warming. The climate records of the Battleford region (west central Saskatchewan) indicate that mean annual temperatures have risen by 0.71 °C and mean annual minimum temperatures have risen by 1.03 °C from 1894 to 2007. Snowfall has also increased but total precipitation has not. Concomitant with periodic declines in precipitation, lake elevation has declined and salinity has increased in Jackfish and Murray lakes from 1938 to 2004. This long term increase in salinity is predicted to have caused an approximate 30% loss in diversity of macrobenthos. Phosphorus concentrations have also increased significantly, and Jackfish and Murray lakes would be classified as eutrophic by freshwater trophic indices. However, despite large increases in nutrients in both lakes, algal biomass has not increased and water transparency has not decreased. Although the total amount of planktonic biomass in Jackfish and Murray's food web is similar to that of freshwater lakes, these lakes contain very low algal biomass (measured as chlorophyll a). In fact, such low algal biomass has not been previously observed in such dilute systems. The algal community in these shallow Prairie lakes appears to be very sensitive to slight changes in climate, and future climate driven increases in salinity of prairie lakes may result in large reductions in algal primary productivity.