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Episodic Events – Great Lakes Experiment
(EEGLE)

Issue

The episodic re-suspension and subsequent transport of surface sediments profoundly influences biogeochemical processes in coastal ecosystems. In Lake Michigan, re-suspension and transport of the large inventories of nutrients and contaminants deposited over the past few decades (e.g., P, 137Cs, PCBs, Pb) presently results in much greater fluxes to the water column than from all external inputs. In addition, control of biological processes can occur as a result of effects on light and substrate availability and the introduction of meroplanktonic species. The magnitude and episodic nature of these processes in the Great Lakes has been poorly described from a few point measurements or as the residual term in mass balance models. In 1996, NOAA Great Lakes Environmental Research Laboratory (GLERL) scientists monitoring NOAA CoastWatch satellite images tracked the development of a massive turbidity plume that ultimately extended over 10 km off shore and 200 km along the southern coastline of Lake Michigan. These recent satellite observations of suspended sedimentary material in Lake Michigan illustrated a unique opportunity to investigate an annually recurrent major episode of nearshore-offshore transport (Figure 1).

The plume appears to be initiated by a major late winter storm after the melting of surface ice, and it eventually veers offshore along the eastern shore of the lake, coincident with the area of highest measured sediment accumulation in the lake. The inventory of particulate matter in the plume, conducted on April 2, 1996, was approximately equal to the total annual load of fine sediments into the southern basin. Preliminary evidence indicates that this episodic event may be the major mechanism for cross-margin sediment transport in Lake Michigan. This type of event is believed to be ideal for studying internal recycling of biogeochemically important materials, ecosystem responses, and one of the major processes controlling cross-isobath transport in the Great Lakes.

Approach

In August 1997, NCCOS' Center for Sponsired Coastal Ocean Research (CSCOR) and National Science Foundation (NSF)-Coastal Ocean Processes Program (COOP) began a jointly funded study of the impact related to the episodic plume event on sediment and constituent transport and subsequent ecological effects in Lake Michigan. This program, Episodic Events-Great Lakes Experiment (EEGLE), is being coordinated by the NOAA GLERL and is scheduled to include three field years followed by two years of interpretation and product development. Program components include a retrospective analysis of satellite imagery, water intakes, and other data, process and survey cruises, moored current meters, traps and data acquisition instruments and coupled hydrodynamic-sediment transport-ecological modeling. The goal of the program is to characterize the materials in the plume, infer their sources, and assess their potential impact on the cycling and transport of nutrients and contaminants. Results will improve understanding of critical processes that affect the ecosystem, and will support the development of resource management-oriented information and modeling.

The EEGLE project's website link is at http://www.glerl.noaa.gov/eegle/

For more information, contact:
NOAA/NOS/NCCOS/CSCOR
phone: 301-713-3338
e-mail: coastalocean@noaa.gov