Phosphorus Dynamics in Jessie Lake: Mass Flux across the Sediment-Water Interface

Phosphorus is generally considered to be a major growth limiting macro nutrient in aquatic ecosystems (Jorgensen, 1983; Ishikawa et al., 1989; Fox, 1993). Cultural eutrophication of freshwater ecosystems due to anthropogenic sources of phosphorus is well documented (Wetzel, 2001; Lampert and Sommer, 1997; Stumm and Morgan, 1996; Schindler 1974). Studies have shown that in some situations eutrophication can continue even after external anthropogenic sources of phospholUs have stopped (Hu et al., 2001; Lemmin and Imboden, 1987). This has led researchers to examine other causes of eutrophication, including the significance of internal loading of phosphorus released from the sediments (Petticrew and Arocena, 2001; Blais and Kalff, 1995). A history of nuisance algal blooms, fluctuating phosphorus concentrations and trophic level values has been documented in Jessie Lake (Reed and Watkins 1999). Because of this erratic history there is a concern that Jessie Lake is approaching a hypereutrophic state. During the last decade, phospholUs concentration has exhibited an increase of 135% over 6 years from 24 ug/L in 1992 to 57.3 ug/L in 1998 (Reed and Watkins, 1999), placing Jessie Lake in the 90th percentile of total phosphorus concentration in its eco-region (Heiskary and Wilson, 1988). The Carlson Trophic Status evaluated in terms of Secchi disc, phospholUs, and chlorophyll-a concentrations suggested that Jessie Lake ranged in the mesotrophic class in 1992 and in the eutrophic class in 1998 (Redd and Watkins, 1999). The increasing deterioration of water quality in the lake has impacted its ecological conditions, biological species, recreation potential and propeliy value. During the summer of 1998 a fish kill occurred due to the low oxygen levels within the lake. The Clean Water Palinership is a two-phase program that was developed to address water quality and pollution problems in Mhmesota (MPCA, 1995). This program allows local agencies and groups to receive state funding and specialized assistance from state experts. The phases are awarded separately with the first phase addressing resource investigation, a diagnostic study. and implementation plall, and the second phase implementing best management practices developed from the Phase I plan. A Phase I grant application for Jessie Lake was submitted in 1999 and grallted by the Minnesota Pollution Control Agency (MPCA). Prior to the initiation of Phase I, the Itasca Soil alld Water Conservation District (ISWCD) had obtained water quality measurements in 1998 alld 1999, which became the foundation for Phase I sampling. Phase I was initiated in the year 2000 and is a cooperative project that includes: ISWCD, Chippewa National Forest (CNF), Mimlesota Department of Natural Resources (MNDNR), MPCA, the Jessie Lake Watershed Association (JLWA), University of Minnesota, St. Anthony Falls Laboratory (SAFL), Natural Resources Research Institute (NRRI) at Vel1nillion, and the NOlihern Experimental Station- Grand Rapids (USFS). 1