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Lake Michigan Mass Balance Study - Eutrophication

Summary

LMMB Study
Overview Contaminants

Eutrophication caused by excessive nutrient loads has been researched and control strategies have been implemented in the Great Lakes since the early 1970s. Phosphorus is the primary limiting nutrient for phytoplankton in the Great Lakes while silica limitation for the diatoms is possible in the spring. Some of the symptoms of nutrient over-enrichment include excessive algal growth, species composition changes, taste and odor problems, and changes in aesthetics, and hypoxia.

diagram of eutrophication model

The eutrophication model LM3-Eutro is an important component of the suite of mathematical models used in the Lake Michigan mass balance modeling project (LMMBP).  LM3-Eutro examines relationships between nutrients and algal production but also provides support in modeling hydrophobic contaminants, because the model simulates the dynamics of carbon particles (phytoplankton), to which hydrophobic toxic contaminants 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.  LM3-Eutro is a high-resolution framework containing 44,042 water column segments.  The model has 17 state variables, including two phytoplankton classes, a single zooplankton class, and several particulate and dissolved nutrient (including carbon) states.

map of phosphorus inventory on Lake Michigan

The sources, sinks, and lake inventory of total phosphorus were estimated.  Internal recycle (settling and sediment feedback) accounted for the majority of total phosphorus dynamics occurring in the lake.  A significant mass of phosphorus settled to the lake bed, but a large percentage (~ 60%) is recycled back to the water column.  The  tributaries made up the largest external total phosphorus source to the lake, while the atmospheric load was a relatively small component (kg/y).  The total phosphorus export at the Straits of Mackinac and the Chicago diversion were estimated to be a small fraction of the total export.  Overall, the best estimate using the average of the 1994-1995 loads was that there was a 5% annual loss of total phosphorus in the lake, which suggested that there would be a small, but steady, decrease in the total phosphorus lake concentration given constant total phosphorus loads.

Forecast scenarios (using the LM3-Eutro model to project future lake conditions)

charts of constant conditions scenario

Constant Conditions Scenario. The scenario was started on January 1, 1994. A constant user-specified net sediment total phosphorus flux was applied in both space and time. Total phosphorus tributary and atmospheric loads for 1994 and 1995 were repeated in a two-year cycle. Hydrodynamics for 1994 and 1995 were similarly repeated. The model was run until steady-state was achieved. The model reached steady-state within 28 years (2021). The steady-state lake-wide concentrations for total phosphorus and maximum POC were 4.3 μg/L and 0.2 mg/L, respectively, while the values for the spring maximum chlorophyll a concentrations were 2.36 μg/L for the epilimnion and 1.07 μg/L for the hypolimnion.

chart of GLWQA scenario

Scenario related to the GLWQA: The scenario was started on January 1, 1994.  A constant user-specified net sediment total phosphorus flux was applied in both space and time.  The Constant Conditions scenario (see scenario above) was run from January 1, 1994 to December 31, 2004.  Then, through trial-and-error, a total phosphorus load (tributary and atmospheric) that resulted in steady-state total phosphorus concentration of 7 µg/L (the lake-wide International Joint Commission’s [IJC] target) was determined (Great Lakes Research Advisory Board, 1978).  A new user-defined net sediment total phosphorus flux was estimated, assuming that approximately 95% of the phosphorus load was retained in the sediment and 5% was recycled back to the water column.  The IJC total phosphorus concentration target was chosen with the goal of returning Lake Michigan to its “natural oligotrophic state” under the GLWQA (International Joint Commission, 1978).  The model was run to steady-state.  An average annual total phosphorus load of 5,020 MT resulted in a steady-state lake-wide total phosphorus concentration of 7 µg/L.  This equated to a total phosphorus total maximum daily load (TMDL) of 14 MT/d.  This also resulted in a spring epilimnetic maximum chlorophyll a concentration of 3.7 µg/L and a spring hypolimnetic chlorophyll a concentration of 1.6 µg/L.

Publications

Pauer, J.J., A. Anstead, W. Melendez, R. Rossmann, K.W. Taunt, and R.G. Kreis. 2008. The Lake Michigan eutrophication model, LM3-Eutro: Model development and calibration. Water Environ. Res. 80:853-861.

Pauer, J.J., K. Taunt, W. Melendez, R.G. Kreis, and A. Anstead. 2007. Resurrection of the Lake Michigan eutrophication model, MICH1. J. Great Lakes Res. 33:554-563.

Warren, G.J. and R.G. Kreis, Jr.  2005.  Recent and Long-Term Nutrient Trends in Lake Michigan.  In:  T. Edsall and M. Munawar (Eds.), State of Lake Michigan:  Ecology, Health and Management, pp. 141-155.  Ecovision World Monograph Series, Backhuys Publishers, Leiden, The Netherlands.

Reports

Melendez, W., M. Settles, J. J. Pauer, and K. R. Rygwelski.  2009.  LM3:  A High-Resolution Lake Michigan Mass Balance Water Quality Model.  U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Large Lakes Research Station, Grosse Ile, Michigan.  EPA/600/R-09/020, 329 pp.

Pauer, J.J., K.W. Taunt, and W. Melendez.  2006.  LM3-Eutro.   In:  R. Rossmann (Ed.), Results of the Lake Michigan Mass Balance Project:  Polychlorinated Biphenyls Modeling Report, Part 2, pp. 120-182.  U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division-Duluth, Large Lakes and Rivers Forecasting Research Branch, Large Lakes Research Station, Grosse Ile, Michigan.  EPA-600/R-04/167, 579 pp.

Richardson, W.L., D.D. Endicott, R.G. Kreis, Jr., and K.R. Rygwelski.  2004.  The Lake Michigan Mass Balance Project: Quality Assurance Plan for Mathematical Modeling.  U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division-Duluth, Large Lakes and Rivers Forecasting Research Branch, Large Lakes Research Station, Grosse Ile, Michigan.  EPA-600/R-04/018, 233 pp.

Presentations

Pauer, J.J., A.M. Anstead, W. Melendez, and R. Rossmann.  2009.  Small should be the new big: High-resolution models with small segments have big advantages when modeling eutrophication in the Great Lakes. 2009 International Association for Great Lakes Research Annual Conference, 18-22 May 2009, Toledo, Ohio, pp. 172-173 of abstracts.

Pauer, J.J., A.M. Anstead, R.G. Kreis, Jr., and W. Melendez. 2007.  Phosphorus trends in Lake Michigan: what we can learn from measurements, model results and a little common sense.  50th Conference on Great Lakes Research, International Association for Great Lakes Research, Penn State University, College Station, PA., May 28-June1, 2007 (Abstract).

Anstead, A.M., J.J. Pauer, and R.G. Kreis, Jr.  2006.  Estimating Historical TP Loads: Is the "Natural State" of Lake Michigan More Oligotrophic Than We Thought?   Presented at the 26th Annual North American Lake Management Conference, Indianapolis, Indiana. November 8-10, 2006. 

Pauer, J.J., A.M. Anstead, W. Melendez, and R.G. Kreis, Jr.  November 2006.  Managing Phosphorus in the Great Lakes:  Why We Turned to the Past and Not the Present to Predict the Future.  Presented at the 26 Annual North American Lake Management Conference, Indianapolis, Indiana.  November 8-10, 2006.

Anstead, A., J.J. Pauer, and R.G. Kreis, Jr.  November 2005.  Revisiting Historical Phosphorus Loading to Lake Michigan.  Presented at the 25th International Symposium of the North American Lakes Management Society, Madison, Wisconsin.  November 9-11, 2005.

Pauer, J.J., A. Anstead, K. Taunt, R.G. Kreis, Jr., and W. Melendez.  November 2005.  Application of the Eutrophication Model, LM3-Eutro, to Predict Long-Term Phosphorus and Chlorophyll a Concentrations in Lake Michigan.  Presented at the Lake Michigan State of the Lake and Great Lakes Beach Association Conference, Green Bay, Wisconsin.  November 2-3, 2005.

Pauer, J.J., K.W. Taunt, R.G. Kreis, Jr., W. Melendez, and A.M. Anstead.  May 2005.  The Lake Michigan Eutrophication Model, LM3-Eutro:  Results and Application.  Presented at the 48th Conference on Great Lakes Research, International Association for Great Lakes Research, The University of Michigan, Ann Arbor, Michigan.  May 23-27, 2005.

Pauer, J.J., K.W. Taunt, R.G. Kreis, Jr, and W. Melendez.  June 2003.  Development and Application of the Lake Michigan Eutrophication Model, LM3.  Presented at the 46th Conference on Great Lakes Research, International Association for Great Lakes Research, DePaul University, Chicago, Illinois.  June 22-26, 2003.

Rygwelski, K.R. and R.G. Kreis, Jr.  June 2003.  An Overview of the Lake Michigan Mass Balance Project:  Background, Accomplishments, and Future Work.  Presented at the 46th Conference on Great Lakes Research, International Association for Great Lakes Research, DePaul University, Chicago, Illinois.  June 22-26, 2003.

Pauer, J.J., K.W. Taunt, R.G. Kreis, Jr., and W. Melendez.  June 2002.  Resurrecting of the Lake Michigan Model, MICH1: Old Eutrophication Models Never Die.  Presented at the 45th Conference on Great Lakes Research, International Association for Great Lakes Research, University of Manitoba, Winnipeg, Manitoba, Canada.  June 2-6, 2002.

Rygwelski, K.R., R. Rossmann, R.G. Kreis, Jr., and W.L. Richardson.  May 2002.  Linking Great Watersheds and Rivers to Forecast the Impact of Stressors on Large Receiving Waters.  Presented at the U.S. Environmental Protection Agency Science Forum 2002:  Meeting the Challenges, Washington, D.C.  May 1-2, 2002.

Pauer, J.J., W.L. Richardson, W. Melendez, and K.W. Taunt.  June 2001.  Calibration of a High Resolution Eutrophication Model Developed for Lake Michigan.  Presented at the 44th Conference on Great Lakes Research, International Association for Great Lakes Research, University of Wisconsin, Green Bay, Wisconsin.  June 10-14, 2001.

 

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