Environmental status of several Shubenacadie River headwater lakes,Nova Scotia,Canada

The Shubenacadie River basin is the largest watershed in Nova Scotia, Canada, encompassing an area of approximately 2,800 km² and supporting one of the most rapidly expanding populations in Atlantic Canada. A comprehensive study was carried out to assess the effect of recent development in the basin on the headwater lakes. Information on the environmental status of the lakes can be further used in the development of a management framework for the basin with respect to water quality and quantity objectives.Water and sediment quality were investigated in four of the Shubenacadie River headwater lakes. In addition, trophic status of the lakes was assessed by using dissolved phosphorus and oxygen concentrations. The surface area and mean depth of the lakes ranged from 0.83 to 1.13 km² and 4.3 to 6.6 m, respectively. Three of the studied lakes were thermally stratified during the summer. The concentration of dissolved oxygen decreased significantly in the hypolimnion during the stratification period, although the lakes were generally classified as oligotrophic. The water quality is typical for lakes of the area. The pH of the water ranged between 6.1 and 7.3 during the study period. Major ions were chloride, sodium, and sulphate. A significant increase of As, Hg, Zn, Pb, Cu, Ni and Co was found in surface sediments in all four lakes. However, the concentration of these elements in lake water was lower than recommended guidelines for aquatic life and human consumption.