Monitoring water quality of inland lakes, 2007: annual summary report

Elias, Joan; VanderMeulen, David

The Great Lakes Inventory and Monitoring Network (GLKN or the Network) monitors water quality of inland lakes at six national park units: Apostle Islands National Lakeshore (APIS), Indiana Dunes National Lakeshore (INDU), Isle Royale National Park (ISRO), Pictured Rocks National Lakeshore (PIRO), Sleeping Bear Dunes National Lakeshore (SLBE), Voyageurs National Park (VOYA). We began monitoring water quality of inland lakes as a pilot project in 2005 at PIRO and SLBE, continued in 2006 at VOYA and INDU, and expanded to all six parks in 2007. Index lakes (N = 33) were sampled three times during the open water season in 2007. 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. Preliminary results show most lakes to have relatively good water quality, although many lakes exceed the reference criteria for their ecoregion, as established by the USEPA. Calculations of trophic state indices show most index lakes to be mesotrophic. A general pattern of increasing pH, conductivity, and alkalinity exists from west to east, across parks. Dissolved organic carbon shows the opposite pattern, decreasing from west to east. Results from 2006 and 2007 are presented for each park individually and comparisons across parks are discussed. Park specific recommendations are provided. Monitoring will be conducted again in 2008 at the same index lakes, with few exceptions.

Monitoring water quality of inland lakes, 2007: annual summary report

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