Episodic Events: Great Lakes Experiment (EEGLE)

Report on activities: August, 1997 - May, 1998

In August, 1997 the NOAA-Coastal Ocean Program (COP) and National Science Foundation-Coastal Ocean Process (CoOP) began a jointly funded program to study the impact of episodic plume events on sediment and constituent transport and subsequent ecological effects in Lake Michigan. This program, Episodic Events: Great Lakes Experiment (EEGLE), is being coordinated by GLERL and is scheduled to include three field years and two years of subsequent interpretation and product development.

This first year, we have been fortunate to add three new activities to the EEGLE program in addition to those supported by NOAA-COP and NSF-CoOP. The EPA-Great Lakes National Program Office has provided their 180' research vessel for a winter cruise and funded an important study to examine the impact of the plume on PCB cycling. NOAA-GLERL has provided funding for the Physical Group of the Canada Centre for Inland Waters to deploy 5 ADCP current meters and 2 meteorological towers and for the purchase and deployment of pressure sensors to measure waves under ice.

EEGLE presently involves four funding sources and seventeen participating research institutions. Program components include a retrospective analysis of satellite imagery, water intakes, and other historical data, process and survey cruises, moored current meters, traps and data acquisition instruments and coupled hydrodynamic/sediment transport/ecological modeling. Our goal 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. Further program information is available on the web at http://www.glerl.noaa.gov/eegle.

Attempts to mass balance nutrients and contaminants in the Great Lakes have implied that resuspension of contaminated sediments contributes many times the sum of all external inputs. We are evaluating this annual winter-spring resuspension event in order to estimate its impact on internal cycling of constituents, such as nutrients and contaminants, and subsequent effects on lake ecology. Results will improve our understanding of critical processes that affect the ecosystem, and will support the development of a management-oriented information and modeling system.

During its first year, the program was fortunate to have the opportunity to examine a very large plume event. To place it in context, only once before, in its 37 years of intake turbidity records, did the St. Joseph water treatment plant experience an event of similar magnitude. Extensive satellite imagery illustrates the extent of the event in space and time.

Although not scheduled to be a full field year, efforts were made to exploit the opportunity of examining this rare event. Seventeen cruises on four different vessels totaling approximately 60 days and a one day Coast Guard helicopter drifter deployment flight have been completed so far. Five transects were established and sampled during many of the individual cruises. Cruise foci included moorings (below left), survey (below right), process, and Lagrangian.

Cruise Images
Instrument rack holding Vector Averaging Current Meters on deck of R/V Shenehon EEGLE scientists making final preparations on deck of R/V Shenehon before deploying a sequencing sediment trap
EEGLE scientist working in the nutrients lab of the R/V Lake Guardian R/V Lake Guardian (EPA/GLNPO) off of St. Joseph, Michigan
Towed Plankton Survey System (PSS) being lowered over the side of the R/V Lake Guardian EEGLE scientist monitoring a large volume TSM sample on deck of the R/V Laurentian

Activities and accomplishments in the first year. In addition to extensive sampling of the plume and background environments, several new instruments underwent testing during this first year, some with immediate success, while others are still going through modifications. Most recently, all 11 sequencing traps were successfully retrieved and only one appears to have failed. Along with the extensive ship-collected samples and current meter moorings, these 230 samples provide good coverage of the event. Preliminary findings from our efforts include:

Products and outreach. An EEGLE Products web page was constructed and has been continuously updated. It provides details of our outreach and many other items. Briefly, 1500 copies of a 2 page handout have been distributed. There have been coordinated press releases, eleven newspaper articles, and several presentations on the radio or to community groups during this first year.

Plans for our second year. Survey cruises will continue throughout the summer to evaluate the plume's effect on the lake ecology. Current meters (15) are scheduled for retrieval in June and deployment of more extensive mooring arrays (current meters and traps) are scheduled for summer/fall. Most of our planned effort in the summer will be the interpretation of the first years' data. This will be discussed and integrated at our next all-hands meeting, Oct 14-16, 1998. Further interpretation will be made as part of a Special Session at the Feb, 1999 ASLO meeting in Sante Fe, NM.