1. Great Lakes Offshore Biological Desert and the Nearshore Slime Around the Tub David Rockwell Monitoring Indicators and Reporting Branch US EPA, Great Lakes National Program Office

2. Methods Great Lakes National Program Office Annual monitoring cruises, 1983-2005 –Spring unstratified (April) –Summer stratified (August)

3. GLNPO Biology Program Measures Phytoplankton –Community Composition, Biomass –Deep Chlorophyll Maximum –Historical Communities Crustacean Zooplankton and Benthos –Community Composition –Size Structure of Community

4. GLNPO Sampling Stations Different colors indicate regions assumed to be homogeneous

5. Methods 1984-1990: –Tows B-2 m –63  m mesh net with flowmeter –Biomass calculated from avg. length/spp generated from 20 m tows 1998-2005 –100 (or B-2 m) tows –153  m mesh net with flowmeter –20 individuals/spp measured/sample

6. Mary Balcer Richard P. Barbiero University of Wisconsin-SuperiorCSC, & Loyola University Chicago Zooplankton Communities in Lake Huron 1984-2005

7. Total crustacean biomass with standard error bars

8. Daphnia Bosmina Cyclopoid copepod Diaptomid copepod Limnocalanus #1 #3 #2 CladoceransCopepods Bosmina

9. Biomass of major taxonomic groups

10. Diporeia Decline

12. Size distribution of crustacean biomass North Basin South Basin

13. Superior central basin Huron northern basin Diaptomus sicilis Limnocalanus macrurus Lake Huron and Lake Superior Zooplankton Communities

14. Phosphorus Loading Trends Recent Loads Dolan and McGunagle 2005 Michigan P Load (tonnes yr -1 ) Superior Erie Ontario Huron GLWQA Target

15. Total Phosphorus Trends (Spring) Harvey Bootsma SOLEC 2006 Michigan TP (  g L -1 ) ♦ ■ ■ ♦ Environment Canada USEPA-GLNPO Huron Ontario Erie Central Superior GLWQA Target

16. Plots of simulation results and data for TP (  gP/L) in the Upper Great Lakes: (a) Superior, (b) Michigan, and (c) Huron. The water-quality objectives are shown as dashed lines. (RWG D Annex 3 Technical Subgroup Report DePinto et al 2006) Schematic of a long-term, total phosphorus model for the Great Lakes (Chapra 1977).

21. Nearshore Shunt Hypothetical Construct Hecky et al 2004 Can.J. Fish Aquat. Sci 61

22. Data provided by MMSD Mussel invasion Secchi disk depths near Milwaukee, Lake Michigan Dr. Harvey Bootsman, SOLEC 2006 Data source: MMSD

23. Cladophora

25. Lake Erie Total Phosphorus, ug-P/L Pre(1983-1989)/Post (1990-2004)

26. Lake Erie Total Dissolved Phosphorus, ug-P/L Pre(1983-1989)/Post (1990-2004)

27. DRP/TP Maumee Sandusky Cuyahoga Grand Figure courtesy of Dr. Peter Richards, Heidelberg College

28. Sandusky and Maumee River Watersheds Lake Erie Figure courtesy of Dr. Peter Richards, Heidelberg College

29. Average [P] (ppm) P in Wisconsin Cropland Bundy and Sturgul 2001

30. P Input to soil Water [P] Soil [P] Sediment [P] Years Source: S.R. Carpenter, 2005 Long-term Influence of Soil P on Lake P Soil P inputs reduced after year 250 Phosphorus Density (g m -2 ) P Inputs to Soil (g m -2 y -1 )

31. Average [P] (ppm) Soil P Storage Change (kg ha -1 ) P in Wisconsin Cropland Bundy and Sturgul 2001

32. Phosphorus Density (g m -2 ) P Inputs to Soil (g m -2 y -1 ) Long-term Influence of Soil P on Lake P Soil P budget balanced at year 250 P Input to soil Water [P] Soil [P] Sediment [P] Years Source: S.R. Carpenter, 2005

33. Summary Offshore Declines in Zooplankton Biomass are observed Lake Huron. Phosphorus loads and open lake phosphorus concentrations have declined in the Great Lakes in response to controls Top down effects are observed to contribute to decline in the lower food web. Nearshore Cladophora increases appear to be link to Dreissena invasion via increased water clarity and cycling of nutrients Total phosphorus loading has increased soluble fraction and open lake concentrations in Lake Erie have a significant increase in soluble fraction in the spring. Total phosphorus concentrations in the Upper Great Lakes appear to below levels modeled to exist in 1800.

34.  In the nearshore zone, increased water clarity has altered the relationship between P supply and algal abundance.  More P abatement would benefit the nearshore zone, but would it benefit pelagic zone?  Dissolved Reactive Silica increases in Lakes Michigan and Huron are linked to TP declines.  Dissolved Reactive Silica increases in Lake Erie are linked to predation by Dreissena  Nearshore shunt of nutrients redirected to the nearshore zones of the Lakes contributing to the reemergence of Cladophora while offshore P concentrations remain low.  Continued addition of P to soils may pose a challenge to the lakes well into the future.