1. Phosphorus in the Great Lakes:
The Rules Have Changed
Harvey Bootsma

2. Great Lakes Water Quality Agreement
Total Phosphorus Target Concentrations:
Lake Superior = 5 mg / L
Lake Michigan = 7 mg / L
Lake Huron = 5 mg / L
Lake Erie = 10 / 15 mg / L
Lake Ontario = 10 mg / L
Targets set as part of GLWQA. Why phosphorus? It’s the “limiting nutrient”.

3. P loading trends in the Great Lakes
To meet concentration targets, loading targets were set. Before setting these, scientists and managers had to understand how P behaved in the lakes, so they could predict how changes in P load would affect P concentration. As you can see, loading targets for most lakes have been met. But occasional exceptions in Erie and Ontario.
Dolan and Chapra, 2012

4. Lake Erie Algal Bloom NOAA / NASA
We had algal problems in the 60’s and 70’s, and then thought we had solved the problem. But in the past 10 years, the monster of eutrophication has raised its ugly head again. The question is: why?
NOAA / NASA

5. Phosphorus Concentrations in Lake Erie
TP concentrations in Erie have generally increased over the past two decades. It’s now above the 10 ug/L target.
EPA, Great Lakes National Program Office

6. More P is in dissolved reactive form
All phosphorus is not the same. In addition to increased P loading, the forms of P have changed. Now more of the P is the type that algae can use.
P. Richards, Heidelberg College

7. Hypoxia in Lake Erie
Lakes need P and they need algae to support the food web. But you can have too much of a good thing. Excess algae sinks to bottom, decomposes, and uses of oxygen. The result is loss of important food web components.
Stuart Ludsin, The Ohio State University
Tom Johengen, U. of Michigan CILER

8. Factors favoring toxin-forming cyanobacteria (blue-green algae)
1. High dissolved phosphorus concentrations.
2. Warm temperatures.
3. Calm conditions.
4. Selective grazing by zebra mussels and
quagga mussels.
The other major impact: toxic algae. Increased P loading and invasive mussels have combined to create a perfect storm for nuisance and harmful algae.
5. Alteration of nitrogen : phosphorus ratio by
mussels.

9. Soil P Storage Change (kg ha-1)
P in Wisconsin Cropland
Average [P] (ppm)
2000- 04
Soil P Storage Change (kg ha-1)
One of the causes: increased P in agricultural soils. Higher than needed by most crops.
Bundy and Sturgul (2001)

10. P in New York Cropland Ketterings et al. (2005)
Likewise in New York state.
Ketterings et al. (2005)

11. Figure provided by Potash and Phosphate Institute
In Ontario farmland, P inputs were previously much higher than removals.
More recently, a balance between inputs and removal is being approached.
Figure provided by Potash and Phosphate Institute

12. Long-term Influence of Soil P on Lake P
Soil P inputs reduced after year 250
Soil [P]
Sediment [P]
P Inputs to Soil (g m-2 y-1)
Phosphorus Density (g m-2)
We are
here
Water [P] at current input
Carpenter’s soil – lake P model.
Soils have a huge store of P, with a very slow turnover time.
Even if P inputs to soil are decreased, soil and lakes will respond very slowly.
Water [P]
Net P Input to soil
Year
Source: S.R. Carpenter, 2005, Proc Nat. Acad. Sci. 102:

13. Milwaukee River Transect, April 2005
So how do we manage the “phosphorus shunt”? Our only option remains to control P loading to the lake. Need to know where the P is coming from. We know agriculture is important, but urban sources, such as runoff and storm sewers are probably also important.
SRP (mg L-1)

14. Mean Depth (m) Vollenweider (1968 Horne & Goldman (1983)
Phosphorus Loading (g P m-2 year-1)
The problem is more challenging for shallow lakes than for deep lakes.
Mean Depth (m)
Vollenweider (1968
Horne & Goldman (1983)

15. Annual P Load Total P in Lake (metric tons) (metric tons)
Huron 3, ,843
Michigan 3, ,760
The lakes contain more P than what is loaded annually. So algae can really be influenced by how P is processed within a lake.

16. Tom Nalepa, NOAA GLERL

18. Nearshore Phosphorus loads, May – July 2006
10 km
Milwaukee region
Nearshore Phosphorus loads,
May – July 2006
Cladophora zone
River load:
120 mg P m-2
Milwaukee R.
Menomonee R.
Mussel Excretion:
506 mg P m-2
Kinnickinnic R.
Mussels have removed P from the water, and made it more concentrated on the lake bottom. If you are an alga that grows on the lake bottom, this makes you happy.
10 km

19. And here is the algae that grows on the lake bottom
And here is the algae that grows on the lake bottom. Impacts tourism, power plants, human health, and food web.

20. Big change in summer chlorophyll
If you’re an alga living in the water column, this is bad.

21. Pelagic prey fish: lakewide fall survey (9-110 m)
And if you’re a fish that feeds on this plankton, it’s also bad.
USGS-GLSC bottom trawl survey

22. Management Challenge: The Phosphorus Conundrum
Will a reduction in P loading fix the Cladophora problem?
Will a reduction in P loading exacerbate the problem of low plankton production offshore?
The rules of the game have changed. We need to determine the P loading “sweet spot” for each lake.
Linking agricultural and water quality management.
Some important questions.

23. Green Streets Stormwater Retention Plan

24. Syracuse, NY

25. Porous pavement

27. MMSD 2020 Water Quality Initiative
MMSD Greenseams Program

30. Lake Whitefish Condition
Madenjian et al. 2002

31. Baumann and Walling (2013)

32. Baumann and Walling (2013)

34. UK water company Thames Water is now extracting phosphate from sewage waste

35. Graph showing world phosphate rock production, 1900–2012, reported by US Geological Survey

40. 18 %

41. Laundry Detergent

42. Changing agricultural practices

43. Improved sewage treatment