Monitoring water quality of inland lakes, 2008: annual summary report
Elias J. 2009. Monitoring water quality of inland lakes, 2008: annual summary report. GLKN/2009/01. Great Lakes Inventory and Monitoring Network. Ashland, Wisconsin
The Great Lakes Inventory and Monitoring Network monitored water quality of inland lakes at six national park units in 2008: Voyageurs National Park (VOYA), Apostle Islands National Park (APIS), Isle Royale National Park (ISRO), Pictured Rocks National Lakeshore (PIRO), Indiana Dunes National Lakeshore (INDU), and Sleeping Bear Dunes National Lakeshore (SLBE). Thirty-three index lakes were sampled three times during the open water season in 2008. Field measurements included depth profiles of temperature, pH, conductivity, and dissolved oxygen; water clarity; and water level relative to a benchmark. Water samples were collected for laboratory analyses of nutrients (total phosphorus, total nitrogen, nitrate+nitrite-nitrogen, ammonium-nitrogen, dissolved silica), major ions (calcium, sodium, magnesium, potassium, sulfate, chloride), dissolved organic carbon, alkalinity, and chlorophyll-a. Results show that many lakes exceed the U.S. Environmental Protection Agency (USEPA) water quality reference criteria for their ecoregion. Tropic state indices show most index lakes to be mesotrophic. Water levels generally declined over the course of the season. Park specific recommendations are provided. Monitoring will continue in 2009 at the same index lakes.