Brian J. Eadie¹, Margaret B. Lansing¹, Andy Winkelman², Brandon Giroux², and Craig Riley^2
1NOAA-GLERL and ²CILER

Objectives:

1. quantify the distribution of particle concentrations and settling materials associated with episodic events and place them in an annual context, and
2. characterize the organic and nutrient composition of these materials for the purpose of estimating constituent fluxes.

Approach:

• Moorings of sequencing sediment traps were deployed to examine mass flux events in the southeastern region of the lake and at offshore stations to seek both local and whole-lake responses (see Fig 1 and Fig 2).
• Moored transmissometers and sequencing water samplers were deployed in the southeastern region of the lake to measure suspended solids and provide samples for compositional analyses.

Results:

• Annual mass fluxes are strongly concentrated during the period of episodic events and there is lake-scale synchrony in the mass fluxes for major events (see Fig 3).
• Large amounts of resuspended coastal sediments, and associated constituents, get transported offshore to the middle of the lake. Estimates of mass and total phosphorus resuspension for the southern basin (table) are greater then total annual external loads.

Episodic Event Flux Calculations for the southern basin of Lake Michigan

Interval	Calculation Basis	Mass (106 MT)	TP (103 MT)
Annual External Load	IJC (1995)	1	2 - 3
Day - April 10, 1996	Calibrated Satellite Image	1	1
Month - March, 1998	Model (Lou et al, 1999)	4
Month - March, 1998	Traps	5	7
Seasonal - Unstratified, 1998	Traps	22	28
Seasonal - Unstratified average	Traps (1980-99; n=8)	13 +/- 7	18 +/- 8

Lou, J., D.J. Schwab, and D. Beletsky (1999). Suspended sediment transport modeling in Lake Michigan. Proceedings of the Canadian Coastal Conference.

IJC (1995). State of the Great Lakes.