Wells Budd, J. Michigan Technological University, jrbudd@mtu.edu
Chye, J. Michigan Technological University, jdchye@mtu.edu

Archived remotely sensed imagery represents a rich, though underutilized, resource for retrospective studies of water parameters in the Great Lakes. Advanced Very High Resolution Radiometer (AVHRR) visible and thermal infrared data formed the basis of a ten-year retrospective study (1987-1996) of surface thermal features and turbidity plumes in central Lake Superior and southern Lake Michigan. The objective was to assess the relationship of winter ice formation, coastal plume development, and thermal bar movement to cross-margin transport phenomena using the remotely sensed imagery. The AVHRR imagery provides rich details of mesoscale (100-1000 km²) surface phenomena, but the relatively coarse spatial resolution of 1.1 km² precludes enumeration of fine scale events. Advanced data visualization products are under development to combine imagery collected simultaneously using AVHRR thermal infrared and SeaWiFS (Sea-Wide Field-of-View Sensor) ocean color imagery. This new class of products will allow us to co-locate thermal and biological fronts, greatly aiding our analyses.

Meadows, L. A. University of Michigan, lmeadows@engin.umich.edu
Vesecky, J. A. University of Michigan, jfv@engin.umich.edu
Teague, C. Stanford University, cal@star.stanford.edu
Hansen, P. E. University of Michigan, pehansen@umich.edu
Paduan, J. Naval Postgraduate School, paduan@oc.nps.navy.mil
Fernandez, J. California State University-Monterey Bay, daniel_fernandez@montery.edu
Daida, University of Michigan, daida@engin.umich.edu
Miller, G. S. Great Lakes Environmental Research Laboratory, gerald.miller@noaa.gov

Over the past three decades, HF radar has become an increasingly important measurement tool for oceanography and related applications. The utility of this technique for measuring regional coastal ocean currents, waves and wind was recently tested over freshwater as a first stage experiment in the comprehensive EEGLE research project (The Impact of Episodic Events on Nearshore-Offshore Transport in the Great Lakes). The objective of the HF portion of the research program is to obtain real-time measurements of these key air and water variables necessary for observational, modeling and forecasting activities. To this end, a multi-frequency HF radar (MCR) was deployed at two sites along the shore of southern Lake Michigan (near St. Joseph, Michigan) to provide observations of near surface current and current shear, wind direction and wave height over an area of about 2500 sq. km. These observations covered the same time period in early May 1998 and geographical region where moored current meters and other in-situ instrumentation were placed. Radial current measurements from the HF system are compared with point measurements at several locations. Encouraging results signify the utility of the HF radar for use in freshwater applications with less aerial coverage than over salt water.

Bedford, K. The Ohio State University, bedford.1@osu.edu
Zhang, S. University of Minnesota, sxz@msi.umn.edu
Sadayappan, P. The Ohio State University, saday@cis.ohio-state.edu
Welsh, D. The Ohio State University, welsh@huron.eng.ohio-state.edu

As part of the NSF/NOAA Episodic Events Program in Lake Michigan, a wave/current/sediment- transport modeling system has been developed in a massively parallel computing regime for more realistic simulation of the near shore processes. The multi-dynamical processes included are currents, surface wave propagation, bed forms and sediment transport occurring in shallow water bodies. The technical aspects being carried out in this project cover: (1) Parallelization of the circulation model (CH3D), wave generation and propagation model (WAM), sediment transport model (SED) and bottom boundary layer model (BBL); (2) Development of appropriate physics interfaces to account for the dynamical interactions among current circulation, wave propagation and sediment transport in coastal environments; (3) Computer integration of the individual parallel codes based on the developed physics interfaces. This newly developed modeling system has been applied to simulating the transport processes associated with the annual episode of spring sediment resuspension along the southern shores of Lake Michigan. Besides addressing the effectiveness of the parallelization and multiple code integration via the use of MPI, this paper focuses on the understanding of the complicated dynamical interactions of wave/current/sediment-transport. The impacts on the prediction of wave propagation and sediment transport will be demonstrated by showing the differences between the simulations, which do and do not include the multiple dynamical interactions.

Eadie, B. J. NOAA - GLERL, brian.eadie@noaa.gov

Lake Michigan is a virtually enclosed basin with a hydraulic residence time of approximately 100 years. Extensive sediment-water coupling during the six month unstratified period has been reported and is required to close large mass-balance inequities for nutrients and contaminants. Recent satellite imagery and sediment trap studies have shown that the majority of sediment resuspension and transport is episodic, primarily in the February-April period. Events in southern Lake Michigan in 1996-98 resuspended more fine-grain sediments (>1MMT) than the estimated total annual external load. Based on water intake turbidity records, the 1998 event was the most intense in 37 years. During the main resuspension event in March, 1998 mass fluxes (<62um particles) in near-coastal traps increased from 16 to 876 g/m²/d and the flux of total phosphorus from 12 to 380 mgP/m²/d. The intensity, duration, and timing (relative to stratification and the beginning of the spring plankton bloom) of these episodic events are being investigated to estimate their impact on lake ecosystems on annual time scales.

Hornbuckle, K. C. University of Iowa, kchorn@engineering.uiowa.edu
Bogdan, J. C. State University of New York at Buffalo, jjbogdan@acsu.buffalo.edu

Atmospheric deposition is an important component of the whole-lake cycling of many organic compounds in Lake Michigan. We hypothesize that the magnitude of atmospheric deposition of persistent organic compounds (pops) is at least partly dependent on the partitioning behavior of the compounds between water and sediment in the water column as well as seasonal meteorological/hydrological events. To test this hypothesis, we have collected air, water and sediment trap samples before (Jan. 1998) and during (March 1998) a major sediment plume event in Lake Michigan. These samples were collected in coordination with EEGLE (episodic events - Great Lakes experiment), a large physical and biological study of the plume event. They were analyzed for a suite of 32 polycylic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Concentrations of the PAHs were highly variable in space during the two sampling periods. For example, total dissolved phase PAHs ranged from 407.82 and 27,550.57 ng/m³. Some of this variation can be attributed to the plume event.

Lohrenz, S. E. University of Southern Mississippi, steven.lohrenz@usm.edu
Schofield, O. E. Rutgers Unversity, oscar@ahab.rutgers.edu
Fahnenstiel, G. L. NOAA, Gary.L.Fahnenstiel@noaa.gov
Millie, D. F. USDA, dmillie@nola.srrc.usda.gov

A diatom bloom is a consistent feature of southern Lake Michigan during the spring isothermal period, which typically coincides with a recurrent coastal turbidity plume (RCP). Although light availability is believed to be important in regulating the bloom, the impact of the RCP is unclear. The recurrent coastal turbidity plume was particularly intense during the 1998 season with peak activity occurring in mid-March. Inherent and apparent optical properties of the RCP and adjacent waters were characterized using a combination of in situ instrumentation and in vitro spectrophotometric methods. Data were used to evaluate the hypothesis that spatial and temporal variations in photosynthesis and growth of phytoplankton were related to optical properties. Optical profiles included spectral measurements of downwelling irradiance, upwelling radiance, beam attenuation and absorption. Mean irradiance in the plume was <30% of that outside the plume. In the RCP, attenuation was 2-3 times higher, largely due to increased absorption. In contrast, scattering was only slightly higher within the RCP. Spectrophotometric analyses revealed that absorption was dominated by non-pigmented suspended particles and chromophoric dissolved organic matter. The intense RCP event was apparently responsible for a reduced intensity and altered composition of the spring diatom bloom (see Millie et al.).

Cotner, J. B. Department of Ecology, Evolution and Behavior, University of Minnesota, cotne002@tc.umn.edu
Johengen, T. B. NOAA Great Lakes Environmental Research Laboratory, johengen@umich.edu
Biddanda, B. A. Department of Ecology, Evolution and Behavior, University of Minnesota, bidda001@tc.umn.edu

An important paradigm in microbial ecology is that secondary productivity is constrained by temperature in cold water systems. We examined bacterial production and biomass during a recurrent sediment resuspension event in Lake Michigan. We found that, in spite of extremely cold temperatures (<2 degrees C) and low primary production, bacterial productivity in the plume was comparable to rates measured in the summer. Productivity during peak plume development was commonly greater than 20 and as high as 50 ug C/L/d. For comparison, summer values in southern Lake Michigan average ca. 30 ug C/L/d. There was a strong correlation between total suspended material and bacterial production (r^2=0.70) during the resuspension event suggesting that particulate matter associated with the plume may provide nutrients that stimulate production. Survey data did not indicate increased DOC concentrations in the plume but P concentrations were elevated where the plume was most developed. These observations suggest that winter bacterial production can represent an important carbon and nutrient flux in Lake Michigan and may be temporally de-coupled from primary productivity.

Kerfoot, W. C. MTU, wkerfoot@bioserver.bio.mtu.edu

The development of a seed bank of resting eggs depends upon yearly production, hatching schedules, survival during burial, and long-term viability. In low sedimentation regions, losses from benthic consumers may limit the development of a seed bank, whereas in productive waters with high sedimentation, the numbers of viable resting eggs may be impressive. Large storm events are important in purging a portion of the buried eggs from the seed bank, resurrecting both ancient genotypes (intraspecific component) and species (interspecific component). On the scale of decades to centuries, the frequency of episodic events could be important for maintaining genetic and community diversity. Examples from small (Lake Michigamme, Portage Lake) and large (Lake Michigan, Lake Superior) lakes are used to clarify aspects of the model development.

Schwab, D. J. NOAA Great Lakes Environmental Research Laboratory, david.schwab@noaa.gov
Beletsky, D. J. Department of Naval Architecture and Marine Engineering, University of Michigan, dima.beletsky@noaa.gov
Lou, J. NOAA Great Lakes Environmental Research Laboratory

Numerical models of hydrodynamic circulation and wind waves can be used to simulate waves, currents and temperatures in a coastal region with very high spatial and temporal resolution. Models of sediment resuspension and transport can be used in conjunction with the hydrodynamic circulation and wave models to estimate bottom erosion and deposition with similar resolution. Because of the large volume of the model output data, it is necessary to use advanced visualization techniques to analyze the computed current, temperature, wave, and sediment concentration fields. In this presentation we will describe techniques for graphical representation of hydrodynamic and sediment transport model output, including computer animation. The impact of episodic events on circulation, waves, and sediment transport is demonstrated using results of multi-year simulations in Lake Michigan. Visualization techniques allow us to examine the complex spatial dynamics of lake circulation, waves, and sediment resuspension, transport, and deposition. Model results for currents, waves, temperatures, and suspended sediment concentrations are compared to field observations during the simulation period. The comparisons show that the best agreement between model results and observations occurs during periods of strong forcing.

Lavrentyev, P. J. University of Akron, peter3@uakron.edu
Gardner, W. J. University of Texas Marine Science Institute, gardner@utmsi.utexas.edu
Cavaletto, J. F. NOAA Great Lakes Environmental Research Laboratory, joann.cavaletto@noaa.gov

A pilot study of the composition and distribution of microbial plankton (bacteria, picocyanobacteria, nano- and microzooplankton) and of nitrogen cycling rates was conducted as a part of the multidisciplinary Episodic Event Great Lakes Experiment (EEGLE) aimed at examining the effects of a recurrent storm-driven coastal plume in southern Lake Michigan. Because of an unusually warm winter, the profound plume initiated in January and lasted through April, thus providing us with the opportunity to observe its effects on the early stages of the seasonal plankton succession. The microbial samples were collected from discrete depths along four transects representing gradients of turbidity off Muskegon, St. Joseph, Gary, and Chicago and are being enumerated. Near-surface ammonium cycling rates were not distinguishable from zero at either a plume station (uptake = 0.010 SE 0.033 uM/h; regeneration = -0.011 SE 0.006 uM/h) or at other stations (uptake = 0.006 SE 0.020 uM/h; regeneration = -0.004 SE 0.028 uM/h).

Millie, D. USDA-ARS, dmillie@nola.srrc.usda.gov
Fahnenstiel, G. NOAA-GLERL, Gary.L.Fahnenstiel@noaa.gov
Schofield, O. Rutgers University, oscar@ahab.rutgers.edu
Lohrenz, S. University of Southern Mississippi, slohrenz@usm.edu

A recurrent plume of resuspended silt- and clay-like particles occurs annually during the spring isothermal period within southern Lake Michigan. Although light availability has been hypothesized to regulate, in part, Lake Michigan phytoplankton, linkages between the plume and the spring diatom bloom are unknown. We are evaluating the impacts of the plume on the lake's phytoplankton and in situ water-column optics. Our intent was to assess the influence of light availability (see Lohrenz et al.) on phytoplankton biomass and associated rate processes. The plume appeared to alter the intensity and composition of the spring bloom; generally, values of total chlorophyll biomass values at stations severely impacted by the plume were slightly greater than values at less-impacted stations. Centric diatoms, particularly species of Cyclostephanos and Aulacoseira, constituted the greatest proportion of the assemblages and appeared to have greater light-harvesting ability (as determined by microphotometric techniques) than other common phytoplankton, possibly explaining their dominance during this episodic event. Although no great differences in bulk P-I parameters were observed, phytoplankton production appeared to be suppressed to a greater degree at nearshore stations severely impacted by the plume than at the less-impacted offshore stations.

Klump, J. Val. University of Wisconsin-Milwaukee, vklump@uwm.edu
Waples, J. T. University of Wisconsin-Milwaukee, jwaples@uwm.edu
Edgington, D. N. University of Wisconsin-Milwaukee, dnedge@uwm.edu
Mackenzie, R. A. University of Wisconsin-Milwaukee, ram@uwm.edu
Szmania, D. C. University of Wisconsin-Milwaukee, sd@uwm.edu
Lovalvo, D. Eastern Oceanics Inc., eoceanics@compuserve.com
Eadie, B. J. NOAA Great Lakes Environmental Research Lab, brian.eadie@noaa.gov
Orlandini, K. Argonne National Laboratory,
Robbins, R. A. NOAA Great Lakes Environmental Research Lab, john.robbins@noaa.gov

The nearshore zone (< 40 meters depth) within southern Lake Michigan is characterized by a diverse array of bottom types from cobble and boulder fields, to sand and gravel bottoms, to hard clay banks. Despite a lack of permanently accumulating sediments within most of this region, it is an area of intense and episodic sediment resuspension. It is hypothesized that the nearshore bottom serves as a temporary repository for sediments entering the lake and that this resuspension initiates both alongshore and shore normal transport of fine-grained particles. Techniques are being developed to quantitatively measure the inventories of sediments and radionuclides (Th-234, Pb-210 and Cs-137) temporarily residing in this transient particle pool. Changing inventories may provide information on the frequency and duration of resuspension, on the residence time of particles in the nearshore benthic system, and on the cross-margin transport of particulate materials to zones of permanent deposition and burial. ROV based observations have also revealed that much of the nearshore area has become colonized by very abundant populations of the zebra mussel (Driessenia polymorpha), an efficient particle filter feeder. Their impact on particle dynamics in the nearshore would appear to be significant. SS52 Poster

McCormick, M. J. NOAA/GLERL, michael.mccormick@noaa.gov
Murthy, C. J. NWRI/CCIW, Raj.Murthy@CCIW.ca
Miller, G. S. NOAA/GLERL, gerald.miller@noaa.gov
Saylor, J. H. NOAA/GLERL, jim.saylor@noaa.gov

Scientists from NOAA's Great Lakes laboratory and Canada's National Water Research Institute are conducting three years of field investigations to study cross-margin transport in Lake Michigan. The major study site is located on the southeast coast of Lake Michigan and 26 current meter moorings have been deployed in this region. The observation strategy is designed to resolve the mean flow and large-scale phenomena including the propagation of topographic waves and coastally-trapped Kelvin waves. An additional goal is to provide a detailed description of the coastal flow field (currents, vorticity, and convergence patterns) and understand coastal dynamics during the winter/spring transition period. The results of one recent winter storm are presented which documents a major episode of offshore transport of water in the coastal plume as recorded by current meters and further suggested by satellite imagery.

Waples, J. T. Great Lakes WATER Institute, University of Wisconsin-Milwaukee, jwaples@uwm.edu
Klump, V. T. Great Lakes WATER Institute, University of Wisconsin-Milwaukee, vklump@uwm.edu
Edgington, D. N. Great Lakes WATER Institute, University of Wisconsin-Milwaukee, dnedge@uwm.edu
MacKenzie, R. Great Lakes WATER Institute, University of Wisconsin-Milwaukee, ram@uwm.edu
Szmania, D. Great Lakes WATER Institute, University of Wisconsin-Milwaukee, sd@uwm.edu
Robbins, J. A. Great Lakes Environmental Research Laboratory, john.robbins@noaa.gov
Eadie, B. J. Great Lakes Environmental Research Laboratory, brian.eadie@noaa.gov

The activity of Th-234 (half-life 24.1 days), and its departure from secular equilibrium with its U-238 parent (100 +/- 5 fCi/L) has been measured within the water column of nearshore Lake Michigan. Th-234 activities, both in solution (< 0.45 um) and bound to particles, have been measured on a bi-monthly basis throughout the southern basin of the lake in water depths from 10 to 40 meters. These represent the first activity measurements in freshwater for both soluble and particulate Th-234. Particle concentrations within the coastal margin of Lake Michigan vary dramatically in response to episodic sediment resuspension events, and Th-234 activities reflect time dependent fluctuations in particle loadings, particle settling rates, and particle surface geochemistry. The utility of Th-234 as a tracer for measuring the residence time/behavior of particles has been established by marine scientists. The use of particle reactive tracers, however, has been unexploited by limnologists.