Synoptic water quality survey of selected Halifax-area lakes : 2011 results and comparison with previous surveys / Pierre M. Clement and Donald C. Gordon. : Fs97-4/3170E-PDF

"The fourth synoptic survey of water quality in 51 Halifax-area lakes was conducted on 7 April 2011. Surface samples were collected by helicopter or small boat immediately after ice out when lakes were well mixed. Water quality variables measured included pH, major ions, nutrients, organic matter and trace elements. The results are compared to those of similar surveys previously conducted in 1980, 1991 and 2000. Statistically significant increases over the 31-year observation period were seen in conductivity, sodium, calcium, magnesium, potassium, chloride, alkalinity and nitrate. These increases were more pronounced in lakes with developed watersheds. The highest values for trophic state index (TSI) were found in Settle, Bissett and Rocky lakes indicating eutrophic (nutrient-rich) conditions. Except for pH, chloride, total nitrogen, zinc and arsenic in certain lakes, available guidelines suggest that the existing water quality poses no threat to aquatic life. The mean concentrations compare favourably with those observed in the water quality program conducted by the Halifax Regional Municipality between 2006 and 2011 with sampling in the spring, summer and fall. These synoptic surveys are only a part of the total spectrum of water quality monitoring programs that are needed to ensure the well being of Halifax-area lakes over the long term. Additional studies should have a more detailed spatial and temporal sampling design, cover all seasons of the year, include profiling the entire water column and measure other important variables including oxygen"--Abstract, page x.

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