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Lake Michigan Mass Balance Study - Eutrophication
Nutrients - Eutrophication
LMMB Study
Overview- The Issue: Are sediments, air, land, and water sources or pathways of contamination that affect the integrity of the ecosystem?
- What is the Lake Michigan Mass Balance Study?
- Sample Design and Sample Collection
Eutrophication from excessive nutrient loads and nutrient concentrations has been under investigation and has received control strategies in the Great Lakes since the early 1970s. Phosphorus is the primary limiting nutrient in the Great Lakes and if loads and concentrations are sufficiently great, nitrogen and silica become secondarily limiting nutrients. Some of the symptoms of nutrient over-enrichment include excessive algal growth, species composition changes, taste and odor problems, and changes in aesthetics, among others.
The eutrophication model is an important component of the Lake Michigan mass balance modeling framework to examine relationships between nutrients and algal production but also for hydrophobic contaminants, because it simulates the dynamics of carbon particles (phytoplankton), to which toxics are likely to attach in the water column. For this reason the eutrophication model was applied as part of the overall modeling framework for toxics.
The eutrophication model has also been applied as a stand alone model to specifically examine nutrient and phytoplankton relationships. Phosphorus loads to Lake Michigan are provided in Figure 14.
LMMB Major Findings: Eutrophication
- Fox River 596,000 kilograms per year
- Sheboygan River 22,000 kilograms per year
- Milwaukee River 31,000 kilograms per year
- Grand Calumet River 40,000 kilograms per year
- St. Joseph River 264,000 kilograms per year
- Kalamazoo River 138,000 kilograms per year
- Grand River 351,000 kilograms per year
- Muskegon River 43,000 kilograms per year
- Pere Marquette River 27,000 kilograms per year
- Manistique River 25,000 kilograms per year
- Menominee River 127,000 kilograms per year
- Total phosphorus loads for monitored tributaries 1,664,000 kilograms per year
- Total phosphorus loads for unmonitored tributaries 650,000 kilograms per year
- Lake Michigan phosphorus loads and concentrations are low and below Great Lakes Water Quality Agreement and International Joint Commission targets
- Tributaries are the major source of phosphorus to Lake Michigan
- Highest concentrations can be observed in selected nearshore zones near tributary mouths and in Green Bay
- There is no evidence of increasing loads or increasing concentrations in the open-water through 2002; forecasts indicate relatively stable phosphorus and chlorophyll-a concentrations into the future