GLERL Publication Abstracts: FY 1997

ASSEL, R.A., and S. Rodionov. Laurentian Great Lakes ice cover teleconnections. Proceedings, 21st Annual Climate Diagnostics and Prediction Workshop, Huntsville, Alabama, October 28-November 1, 1996. NOAA Climate Prediction Center and the Earth System Science Laboratory, University of Alabama, Huntsville, 122-125 (1997).

An earlier study (Assel, 1992) provided the motivation for this present research on Great Lakes ice cover teleconnections. Here, annual maximal ice cover for winters 1963-1990 are analyzed to define much-above and much-below average ice cover based on the 7 years with the highest and 7 years with the lowest annual maximum ice coverage. Composite anomaly maps of 700 hPa geopotential height for the lowest (highest) quartile ice cover reveal a zonal (meridonal) flow pattern. The difference between the 700 hPa composite anomaly maps and maps of correlations between all 28 winters of annual maximum ice cover and 700 hPa geopotential heights provide evidence of teleconnectivity for annual maximum Great Lakes ice cover.

BEETON, A.M. Impact of non-indigenous species on the ecosystem of the Laurentian Great Lakes. Proceedings, Second International Lake Ladoga Symposium, Joensuu, Finland, August 26-30, 1996. University of Joensuu, Publications of Karelian Institute, Joensuu, Finland, 368-374 (1997).

No abstract.

BELETSKY, D., W.P. O'CONNOR, and D.J. SCHWAB. Hydrodynamic modeling for the Lake Michigan Mass Balance Project. Proceedings of the Next Generation Environmental Models Computational Methods (NGEMCOM) workshop, G. Delic, and M. F. Wheeler, Bay City, MI, August 7-9, 1995. Society for Industrial and Applied Mathematics, Philadelphia, PA, 125-128 (1997).

A three-dimensional primitive equation numerical ocean model, the Princeton model, was applied to Lake Michigan in support of the EPA Lake Michigan Mass Balance Project (LMMBP). The model has 13 vertical levels and uniform horizontal grid size of 5 km. For the LMMBP, the model will be driven with observed meteorological conditions for the study years of 1994 and 1995. As a model test we chose a case with strong northerly wind in August 1955 to compare Kelvin waves in the model with observations presented by Mortimer (1963). Therefore, the model was driven with an impulsive wind stress imitating the passage of the weather system. Under the strong wind forcing, the thermocline breaks the surface along the eastern shore, and a thermal front appears. After the wind cessation, the edges of this thermal front propagate cyclonically around the lake in the form of a coastally trapped Kelvin wave. Although initially the strong upwelling front in the model compared favorably with observations, the speed of the Kelvin wave in the model was less than the speed obtained from observations.

BELETSKY, D., W.P. O'CONNOR, D.J. SCHWAB, and D. Dietrich. Numerical simulation of internal Kelvin waves and coastal upwelling fronts. Journal of Physical Oceanography July 1997:1197-1215 (1997).

Two three-dimensional primitive equation numerical ocean models are applied to the problem of internal Kelvin waves and coastal upwelling in the Great Lakes. One is the Princeton Ocean Model (POM) with a terrain-following (sigma) vertical coordinate, and the other is the Dietrich/Center for Air Sea Technology (DIECAST) model with constant z-level coordinates. The sigma coordinate system is particularly convenient for simulating coastal upwelling, while the z-level system might be better for representing abrupt topographic changes. The models are first tested with a stratified idealized circular lake 100 km in diameter and 100 m deep. Two bottom topographies are considered: a flat bottom and a parabolic depth profile. Three rectilinear horizontal grids are used: 5, 2.5, and 1.25 km. The POM was used with 13 vertical levels, while the DIECAST model was tested with both 13 and 29 vertical levels. The models are driven with an impulsive wind stress imitating the passage of a weather system. In the case of the flat-bottom basin, the dynamical response to light wind forcing is a small amplitude internal Kelvin wave. For both models, the speed of the Kelvin wave in the model is somewhat less than the inviscid analytic solution wave speed. In the case of strong wind forcing, the thermocline breaks the surface (full upwelling) and a strong surface thermal front appears. After the wind ceases, the edges of this thermal front propagate cyclonically around the lake, quite similar to an internal Kelvin wave. In the case of parabolic bathymetry, Kelvin wave and thermal front propagation is modified by interaction with a topographic wave and a geostrophic circulation. In both models, higher horizontal resolution gives higher wave and frontal speeds. Horizontal resolution is much more critical in the full upwelling case than in the Kelvin wave case. Vertical resolution is not as critical. The models are also applied to Lake Michigan to determine the response to strong northerly winds causing upwelling along the eastern shore. The results are more complex than for the circular basin, but clearly show the characteristics of cyclonically propagating thermal fronts. The resulting northward warm front propagation along the eastern shore compares favorably with observations of temperature fluctuations at municipal water intakes after a storm, although the model frontal speed was less than the observed speed.

Berg, D.J., S.W. Fisher, and P.F. LANDRUM. Clearance and processing of algal particles by zebra mussels (Dreissena polymorpha). Journal of Great Lakes Research 22(3):779-788 (1996).

The exotic zebra mussel, Dreissena polymorpha Pallas, has become a dominant member of nearshore benthic communities in the Laurentian Great Lakes. Suspension-feeding bivalves such as the zebra mussel filter algal particles from the water column and either reject them as pseudofeces, digest them, or egest them as feces. We used laboratory experiments to compare clearance and particle processing of two green algal species by zebra mussels. The effect of algal concentration on clearance rate of Chlamydomonas reinhardtii varied between large and small mussels. When mussels were fed Pandorina morum, clearance rate declined with increasing algal concentration. Mussel size affected clearance of C. reinhardtii but not P. morum. On a diet of P. morum, pseudofeces production was constant across algal concentrations. When fed C. reinhardtii, mussels increased pseudofeces production as algal concentration increased once a threshold was crossed. Below this threshold, no pseudofeces were produced. Measured clearance rates tended to be as high or higher than those previously reported, indicating that incipient limiting concentrations vary with the types of particle processed. Absorption efficiencies were similar for both algal species. Our results show that particle processing by zebra mussels depends on the types of particles present in the water column and the size structure of the mussel population. To accurately determine the impacts of zebra mussels on the trophic structure of ecosystems and the cycling of contaminants, investigators must use realistic algal assemblages and account for the size structure of mussel populations.

BOLSENGA, S.J., M.S. Evans, H.A. VANDERPLOEG, and D.C. NORTON. PAR transmittance through thick, clear freshwater ice. Hydrobiologia 330:227-230 (1996).

Measurements of photosynthetically active radiation through clear freshwater ice 154-158 cm thick varied from 14.8 to 24.8% depending, in this case, primarily on the amount of flocullent material trapped within the ice. Transmittance in one area dropped to less than 1% with the presence of a 3 cm thick snow cover. Extinction coefficients varied from 0.014 to 0.010 cm-1.

CAVALETTO, J.F., T.F. NALEPA, R. Dermott, W.S. GARDNER, M.A. QUIGLEY, and G.A. LANG. Seasonal variation of lipid composition, weight, and length in juvenile Diporeia spp. (Amphipoda) from Lakes Michigan and Ontario. Canadian Journal of Fisheries and Aquatic Sciences 53(9):2044-2051 (1996).

Benthic amphipods, Diporeia spp., were collected during 1988 and 1989 at four sites to compare size and lipid levels of animals living in Lakes Michigan and Ontario: sites were at depths of 45 and 100 m in Lake Michigan and 35 and 125 m in Lake Ontario. In Lake Michigan, the mean length, mass, and lipid levels of individual Diporeia from 45 m were significantly different from those collected from 100 m in 1988; in 1989, only mass and lipid levels were significantly different between depths. In contrast, regardless of the year, the Lake Ontario Diporeia from 35 m were similar in mass and length to those from 125 m, but lipid levels were significantly different between depths. Combined means for total lipid for each lake over similar months revealed higher levels in Lake Ontario than in Lake Michigan Diporeia. Triacylglycerols were the dominant lipid class in all the amphipods, with mean levels reaching a maximum of 84% of the total lipid in individuals from Lake Ontario at 35 m. Trophic state, food-web, and (or) genetic differences are probably responsible for the occurrence of higher lipid levels in Lake Ontario Diporeia than in Lake Michigan Diporeia.

CROLEY, T.E., II. Water resource predictions from meteorological probability forecasts. Proceedings, Sustainability of Water Resources Under Increasing Uncertainty, Rabat, Morocco, April 23-May 3,1997. IAHS Press, Institute of Hydrology, Wallingford, Oxfordshire, 301-309 (1997).

NOAA recently began providing monthly seasonal climate outlooks of expected air temperature and precipitation probabilities. Users can interpret climate outlooks to assess the risk to water resources of extreme meteorological conditions and of variability in general. One important approach uses historical meteorology record segments with hydrological, limnological and other models to simulate hydrological possibilities for the future (preserving observed spatial and temporal relationships). The meteorological possibilities are weighted to be compatible with climate outlook probabilities. The corresponding weighted hydrological possibilities are used to infer water resource probabilities and other parameters. The weights are determined by constructing boundary equations for the weights to match climate outlooks, setting the relative importance of each equation in case incompatibilities arise and solving them for physically relevant values. Their solution becomes an optimization problem for the general case. An example illustrates the concepts and method.

EADIE, B.J. Probing particle processes in Lake Michigan using sediment traps. Water, Air, and Soil Pollution 99:133-139 (1997).

Sediment trap sampling at an offshore site in southern Lake Michigan has continued for an 18 year period with a sampling frequency ranging from weekly to semi-annually. During the 6 month unstratified period sediment trap mass and tracer profiles are nearly constant and they have been used to describe the extent of sediment resuspension. After stratification, mass flux rapidly declines and particle tracers are removed from the epilimnion at the rate of 0.5-1 m.d-1. Exponential profiles of mass flux clearly show the persistence of a benthic nepheloid layer. High frequency sampling with near-bottom sequencing traps show order of magnitude ranges in mass flux over a few day period.

EADIE, B.J., D.J. SCHWAB, G.A. LESHKEVICH, T.H. JOHENGEN, R.A. ASSEL, N. HAWLEY, R.E. Holland, M.B. LANSING, P.J. LAVRENTYEV, G.S. MILLER, N.R. MOREHEAD, J.A. ROBBINS, and P. VANHOOF. Development of recurrent coastal plume in Lake Michigan observed for first time. EOS Transactions 77(35):337-338 (1996).

No abstract.

Edgington, D.N., J.A. ROBBINS, S.M. Colman, K.A. Orlandini, and M.-P Gustin. Uranium-series disequilibrium, sedimentation, diatom frustules, and paleoclimate change in Lake Baikal. Earth and Planetary Science Letters 142:29-42 (1996).

The large volume of water, approximately one-fifth of the total surface fresh water on the planet, contained in Lake Baikal in southeastern Siberia is distinguished by having a relatively high concentration of uranium (ca. 2 nM), and, together with the surface sediments, an unusually high 234U/238U alpha activity ratio of 1.95. About 80% of the input of uranium to the lake, with a 234U/238U ratio of 2.0, comes from the Selenga River. Profiles of uranium, as well as the extent of isotopic disequilibrium in a 9 m sediment core collected on Academic Ridge, generally show high values during interglacial periods corresponding to high diatom frustule numbers (DiFr) and biogenic silica (BSi) data that have been reported elsewhere. During glacial periods (low DiFr and BSi), uranium progeny (238U/232Th) were in secular equilibrium with low concentrations of their parent 238U. Radionuclide distributions were interpreted in terms of a quantitative model allowing for adsorption of riverine inputs of uranium onto two classes of sedimenting particles with differing 238U/232Th ratios and uranium progeny in secular equilibrium. If the 234U/238U activity ratio of adsorbed uranium has remained constant, mean sedimentation rates can be independently estimated as 3.6 ± 0.6 and 3.7 ± 0.9 cm · kyr-1 for the decay of 234U and in-growth of 230Th, respectively. These rates are consistent with a mean rate of 3.76 cm · kyr-1, calculated by optimization of the correspondence between adsorbed 238U and d18 in dated oceanic sediments. The adsorbed uranium apparently tracks variable river flow during interglacials and is drastically reduced during periods of glaciation. Evidently, uranium has not been significantly redistributed within Baikal sediments over at least the past 250 kyr and is a unique, biologically non-essential, tracer for climate-sensitive processes, which provide their own internal geochronometers, potentially useful for ages up to I Myr BP.

GARDNER, W.S., J.F. CAVALETTO, J.B. Cotner, and J.R. JOHNSON. Effects of natural light on nitrogen cycling rates in the Mississippi River plume. Limnology and Oceanography 42(2):273-281 (1997).

Isotope-dilution experiments with 15NH4+ were conducted on near-surface water samples in the Mississippi River plume during May 1992 and July 1993 to quantify community cycling rates for ammonium and determine whether regeneration rates are enhanced by light. Experiments done under natural light in May showed ranges of potential uptake and regeneration rates of 0-0.4, mM h-1 and 0-0.18, mM h-1'. Samples collected offshore from the Atchafalaya River and the Southwest Pass of the Mississippi River in July yielded potential uptake rates of 0.4-1.8, mM h-1 under natural light vs. 0-0.45 mM h-1 in the dark. Ammonium regeneration rates ranged from 0.08 to 0.75 'EM h-1 in the light and from 0.02 to 0.3 mM h-1 in the dark. The observed light/dark regeneration-rate differences imply a close coupling between phytoplankton production and ammonium regeneration. The ratio of bacterial cell specific regeneration to uptake rates increased in the outer regions of the plume, indicating a changing contribution of bacterial-sized organisms to nitrogen cycling processes in different regions of the plume.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. FY 1995 Yearly Report. C.M. Darnell and D.F. Reid (eds.). NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 49 pp. (1996).

No abstract.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Episodic Events: Great Lakes Experiment. Great Lakes Environmental Research Laboratory, 2 pp. (1997).

No abstract.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. GLERL Info Sheet. Great Lakes Environmental Research Lab, 2 pp. (1997).

No abstract.

HARKEY, G.A., S. KANE DRISCOLL, and P.F. LANDRUM. Effect of feeding in 30-day sediment bioaccumulation assays using Hyalella azteca in Fluoranthene-dosed sediment. Environmental Toxicology and Chemistry 16(4):762-769 (1997).

Current protocols for conducting freshwater sediment bioaccumulation tests recommend that food not be added to exposures, whereas toxicity tests require food addition. To determine effects of adding food on exposure, 30-d sediment exposures were conducted with Hyalella azteca to sediment dosed with four fluoranthene concentrations (trace level to 897 nmol/g dry weight). Accumulation was significantly greater in fed versus nonfed animals at all dose levels after 96 h of exposure and continued to be greater aver 30 d in the low dose levels. At sediment concentrations above 478 nmol/g dry weight, survival of unfed animals dropped to 34% after 30 d. After 30 d of exposure, growth and reproduction were observed in fed animals exposed to sediment concentrations 20 to 90 times the expected median lethal concentration (LC50) values for fluoranthene in sediment, according to 10-d studies reported in the literature using sediment with comparable organic carbon concentrations. Samples of sediment in exposure beakers taken from the sediment-water interface (flocculant layer) and I to 2 cm below the interface had large differences in fluoranthene and organic carbon concentrations. The concentration of fluoranthene was 2 to 10 times greater in the flocculant layer, the area inhabited by H. azteca, compared to the deeper sediment. These data raise questions concerning the interpretation of standard toxicity and bioaccumulation tests when food is routinely added.

HAWLEY, N., X. Wang, B. Brownawell, and R. Flood. Rususpension of bottom sediments in Lake Ontario during the unstratified period, 1992-1993. Journal of Great Lakes Research 22(3):707-721 (1996).

Time-series measurements of current velocity and water temperature made at a station in southwestern Lake Ontario between October 1992 and June 1993 are combined with analyses of material collected in a sequencing sediment trap moored at the same location. The results show that local resuspension of bottom material occurred several times during November and December. Analyses of total PCBs and Mirex concentrations were used to infer the origins of the material collected in the traps. Material collected during the fall has multiples sources; in addition to material already in suspension and bottom material resuspended from the immediate area, some material appears to be derived from the Niagara River delta. This is the first reported instance of bottom resuspension in the Great Lakes at depths below wave base during the unstratified period that has been confirmed by current velocity measurements.

Holcombe, T.L., J.S. Warren, L.A. Taylor, D.F. REID, and C.E. Herdendorf. Lake floor Geomorphology of Western Lake Erie. Journal of Great Lake Research 23(2):190-201 (1997).

Bathymetry of western Lake Erie, exceeding in detail any previous bathymetry, is an early result of a project conducted jointly by the U. S. National Oceanic and Atmospheric Administration and the Canadian Hydrographic Service. This bathymetry utilizes the entire archive of historic hydrographic data assembled since 1903 in the U. S. and Canada. Details of bottom configuration for the shallow (<12 m) western portions of Lake Erie are highlighted using a 1- meter contour interval. The islands and reefs bordering and lying within the western basin have bedrock cores which are erosional remnants of the more resistant upper Silurian and lower Devonian dolomites and limestones. Over-deepened channels between the islands have been sites of postglacial nondeposition, and probably erosion, due to intense wind-driven water circulation through these restricted passages. The Pelee-Lorain Ridge is interpreted as a late Wisconsinan end moraine upon which sand deposits have been concentrated. The Point Pelee Ridge is apparently a morainic ridge, capped by sand deposits transported in part by longshore drift converging on Point Pelee. A fan-shaped feature with a surface depth of 10-15 m, which extends to the east of Point Pelee Ridge, may be a former shoreline delta of the Detroit River. This fan-shaped feature may have formed following opening of the Port Huron outlet about 4000 yr bp when the new River was actively eroding its channel and bringing a heavy load of sediment into Lake Eriealthough subaqueous deposition of fan sediments is a possible alternate explanation. Sculptured drift-like features interpreted as relict spits extend northwestward and south eastward from the bedrock reefs in the western basin off Locust Point. Channels on the floor of the western Lake Erie basin underlying the main shipping lanes have been excavated by propeller wash where ship traffic increases speed, resulting in resuspension of bottom sediments. Dump sites for dredge spoils excavated from channels are expressed in the bathymetry by a distinctive hummocky pattern in two areas.

KANE DRISCOLL, S., G.A. HARKEY, and P.F. LANDRUM. Accumulation and toxicokinetics of Fluoranthene in sediment bioassays with freshwater amphipods. Environmental Toxicology and Chemistry 16(4):742-753 (1997).

Two freshwater amphipods, Hyalella azteca and Diporeia sp., were exposed to sediment spiked with radiolabeled fluoranthene at nominal concentrations of 0.1 (trace) to 1,270 nmol fluoranthene/g dry weight. In two experiments, uptake kinetics and mortality were determined over 30-d exposures. Concentrations of fluoranthene in sediment and pore water were also measured. Mean survival of H. azteca was generally high, greater than 90% after 10 or 16 d, and greater than 74% after 30 d. Mean survival was lower for Diporeia, 14% after a 30-d exposure to the highest sediment concentration in experiment 1, and 53% in experiment 2. Tissue concentrations in Diporeia were as high as 2 to 4 umol/g wet weight, a body burden that could be expected to result in death by narcosis. Hyalella azteca did not typically accumulate more than I umol/g wet weight, which is consistent with the lower observed mortality. Apparent steady-state biota-sediment accumulation factors (BSAFs, lipid- and organic-carbon-normalized) for sediment concentrations other than trace level tended to be higher for Diporeia (0.345-0.818) than for H. azteca (0.161-0.612). The BSAFs for trace levels tended to be lower for both species (0.045-0.436) in comparison to higher sediment concentrations. For both organisms, the internal concentration based on body residue was a more reliable indicator of toxicity than were equilibrium partitioning predictions.

KANE-DRISCOLL, S., P.F. LANDRUM, and E. TIGUE. Accumulation and toxicokinetics of fluoranthene in water-only exposures with freshwater amphipods. Environmental Toxicology and Chemistry 16(4):754-761 (1997).

Two 10-d water-only toxicity tests with radiolabeled fluoranthene were conducted with two species of freshwater amphipods, Hyalella azteca and Diporeia sp. For H. azteca, 10-d median lethal concentrations were 564 nmol/L and 481 nmol/L. Tentative median lethal doses, determined from the regressions of body burden of remaining live H. azteca versus survival, were 5.6 and 3.6 mmol fluoranthene/kg wet weight tissue. Diporeia appeared to be less sensitive, because survival in Diporeia was greater than 84% after 10-d exposures. Elimination rates determined for Diporeia, ranging from 0.0011 to 0.0042/h (half-lives of 7-26 d), were much slower than rates determined for H. azteca of 0.128 to 0.188/h (half-lives of 4-6 h). Faster elimination in H. azteca may be related to its greater ability to metabolize fluoranthene. For H. azteca, an average of 17% of its body burden was present as metabolites after 24 h of exposure to radiolabeled fluoranthene, as compared to 5% for Diporeia. For Diporeia, exposure to various water concentrations of fluoranthene for various lengths of time resulted in declines in the conditional uptake clearance rates (ml water cleared/g wet weight tissue/in). A similar, although less dramatic trend was observed for conditional uptake clearance rates in H. azteca.

Kukkonen, J., B.J. EADIE, A. Oikari, B. Holmbom, and M.B. LANSING. Chlorophenolic and isotopic tracers of pulp mill effluent in sedimenting particles collected from southern Lake Saimaa, Finland. The Science of the Total Environment 188:15-27 (1996).

Sediment traps were used to collect settling particles at two stations upstream of a pulp and paper mill and at four stations along the effluent gradient in Southern Lake Saimaa. The particle samples were collected monthly from May to October 1991. Trap materials were analyzed for concentration and stable isotopic composition of organic carbon and nitrogen. The May 1991 trap samples and water and surface sediment samples from the trap locations were also analyzed for chlorophenolics. The trapped particle flux in May was 6.4 g(dry wt.)/m2/day at the station closest to the pulp mill (3.3 km) and decreased to 2.6 g(dry wt.)/m2/day at the farthest station (16.1 km). The organic carbon content of the particles varied from 10.5% to 22.1% and was the highest at the station nearest to the mill. There was a strong point source signal in the nitrogen isotope composition of effluent material. The other sampling times revealed a similar pattern. The total concentration of chlorophenols, chloroguaiacols and chlorocatechols was 0.8, 17.1 and 16.3 g/g (dry wt.) particles, respectively, at the nearest station and decreased downstream. The total extractable organic halogens in particles exhibited a similar concentration pattern to the identified chlorinated compounds. While about 60% of chloroguaiacols and about 90% of chlorocatechols are removed by sedimentation or degradation processes in the recipient area, most of the chlorophenols and adsorbable organic halogens are transported through the system.

LEE, D.H., A.H. CLITES, and J.P. Keillor. Assessing risk in operational decisions using Great Lakes probabilistic water level forecasts. Environmental Management 21(1):43-58 (1997).

A method adapted from the National Weather Service's Extended Streamflow Prediction technique is applied retrospectively to three Great Lakes case studies to show how risk assessment using probabilistic monthly water level forecasts could have contributed to the decision-making process. The first case study examines the 1985 International Joint Commission (IJC) decision to store water in Lake Superior to reduce high levels on the downstream lakes. Probabilistic forecasts are generated for Lake Superior and Lakes Michigan-Huron and used with riparian inundation value functions to assess the relative impacts of the IJC's decision on riparian interests for both lakes. The second case study evaluates the risk of flooding at Milwaukee, Wisconsin, and the need to implement flood-control projects if Lake Michigan levels were to continue to rise above the October 1986 record. The third case study quantifies the risks of impaired municipal water works operation during the 1964-1965 period of extreme low water levels on Lakes Huron, St. Clair, Erie, and Ontario. Further refinements and other potential applications of the probabilistic forecast technique are discussed.

LEE, D.H., T.E. CROLEY, and F.H. QUINN. Lake Ontario regulation under transposed climates. Journal of the American Water Resources Association 33(1):55-69 (1997).

The implications of Lake Ontario regulation under transposed climates with changed means and variability are presented for seasonal and annual time scales. The current regulation plan is evaluated with climates other than the climate for which it was developed and tested. This provides insight into potential conflicts and management issues, development of regulation criteria for extreme conditions, and potential modification of the regulation plan. Transposed climates from the southeastern and south central continental United States are applied thermodynamic models of the Great Lakes and hydrologic models of their watersheds; these climates provide four alternative scenarios of water supplies to Lake Ontario. The scenarios are analyzed with reference to the present Great Lakes climate. The responses of the Lake Ontario regulation plan to the transposed climate scenarios illustrate several key issues: (1) historical water supplies should no longer be the sole basis for testing and developing lake regulation plans; (2) during extreme supply conditions, none of the regulation criteria can be met simultaneously, priority of interests may change, and new interests may need to be considered, potentially requiring substantial revision to the Boundary Waters Treaty of 1909; (3) revised regulation criteria should be based on ecosystem health and socio-economic benefits for a wider spectrum of interests and not on frequencies and ranges of levels and flows of the historical climate; and (4) operational management of the lake should be improved under the present climate, and under any future climate with more variability, through the use of improved water supply forecasts and monitoring of current hydrologic conditions.

LESHKEVICH, G.A., S.V. Nghiem, and R. Kwok. Satellite SAR remote sensing of Great Lakes ice cover using RADARSAT data. Proceedings, Fourth International Conference on Remote Sensing for Marine and Coastal Environments, Orlando, FL, March 17-19, 1997. Environmental Research Institute of Michigan, Ann Arbor, MI, I-126-I-134 (1997).

During winter months, cloud cover over the Laurentian Great Lakes impairs the use of satellite imagery from passive sensors operating in the visible, near infrared, and thermal infrared spectra for ice cover monitoring and analysis. The all-weather, day/night viewing capability of satellite Synthetic Aperture Radar (SAR) makes it a unique and valuable tool for Great Lakes ice identification and mapping providing that data analysis techniques and capability for using SAR data in an operational setting are developed. RADARSAT, an operational satellite carrying a SAR operating at 5.3 GHz (C-Band) with a horizontal polarization, was successfully launched in 1995. This study explores algorithms for Great Lakes ice cover classification and mapping using RADARSAT SAR data. Preliminary analysis of a ScanSAR Narrow scene of western Lake Superior using a supervised (level slicing) classification technique indicates that different ice types in the ice cover can be identified and mapped and that wind has a strong influence on the backscatter from open water. However, further research needs to be conducted on the repeatability and automation of classification and interpretation from scene to scene. During the 1997 winter season, an experiment is planned to acquire shipborne polarimetric backscatter data using the Jet Propulsion Laboratory (JPL) Cband scatterometer together with surface-based ice physical characterization measurement and environmental parameters coincident with RADARSAT overpass.

LESHKEVICH, G.A., D.J. SCHWAB, and G.C. MUHR. Satellite environmental monitoring of the Great Lakes: Great Lakes CoastWatch Program update. Marine Technology Society Journal 30(4):28-35 (1997).

As the CoastWatch regional node for the Great Lakes, the Great Lakes Environmental Research Laboratory (GLERL) obtains, processes, and delivers environmental data and products for the user community. GLERL provides access to near real-time satellite observations and in situ data for the Great Lakes to 41 federal, state, and local agencies and academic institutions. The goals and objectives of the CoastWatch Program directly support NOAA statutory responsibilities in estuarine and marine science, living marine resource protection, and ecosystem monitoring and management. A digital image product suite of 26 images from the NOAA-12, NOAA-14, and GOES 8 satellites is currency being received. Over 32,000 image products have been received and archived since 1990. In addition, in situ and modeled data, including marine and meteorological observations and water level gauge measurements, are also routinely received and made available via dial-in modem or Internet. A new product developed at GLERL, the Great Lakes Surface Environmental Analysis (GLSEA), is a cloud-free, composited surface temperature chart that will include an ice cover analysis overlay during winter months. It is available to CoastWatch data users and is also on the World Wide Web.

LIU, P.C., editor. Nearshore Hydrodynamics studies in Western Lake Michigan. NOAA Technical Memorandum ERL-GLERL 103, Great Lakes Environmental Research Laboratory, (NTIS#PB97-211031INZ) 40 pp. (1997).

No abstract.

LIU, P.C., and G.S. MILLER. Wavelet transforms and ocean current data analysis. Journal of Atmospheric and Oceanic Technology 13(5):1090-1099 (1996).

The recently advanced approach of wavelet transforms is applied to the analysis of ocean currents. The conventional analyses of time series in the frequency domain can be readily generalized to the frequency and time domain using wavelet transforms. An application of wavelet analysis to a set of observer current data acquired during the spring of 1991 in Lake Michigan shows some significant time-localized characteristics that would not be detected using the traditional Fourier transform approach.

LOFGREN, B.M. Climatic impacts of idealized Great Lakes in a general circulation model. Proceedings, American Meteorological Society Conference, Long Beach, CA, Feb. 2-7, 1997. AMS, Boston, MA, 281-284 (1997).

No abstract.

Magnuson, J.J., K.E. Webster, R.A. ASSEL, C.J. Bowser, P.J. Dillon, J.G. Eaton, H.E. Evans, E.J. Fee, R.I. Hall, L.R. Mortsch, D.W. Schindler, and F.H. QUINN. Potential effects of climatic changes on aquatic systems: Laurentian Great Lakes and Precambrian Shield region. Hydrological Processes 11:825-871 (1997).

The region studied includes the Laurentian Great Lakes and a diversity of smaller glacial lakes, streams and wetlands south of permanent permafrost and towards the southern extent of Wisconsin glaciation. We emphasize lakes and quantitative implications. The region is warmer and wetter than it has been over most of the last 12 000 years. Since 1911 observed air temperatures have increased by about 0 11°C per decade in spring and 0 06°C in winter: annual precipitation has increased by about 21% per decade. Ice thaw phenologies since the 1850s indicate a late winter warming of about 2.5°C. In future scenarios for a doubled CO, climate, air temperature increases in summer and winter and precipitation decreases (summer) in western Ontario but increases (winter) in western Ontario, northern Minnesota, Wisconsin and Michigan. Such changes in climate have altered and would further alter hydrological and other physical features of lakes. Warmer climates, i.e. 2 x CO, climates, would lower net basin water supplies, stream flows and water levels owing to increased evaporation in excess of precipitation. Water levels have been responsive to drought and future scenarios for the Great Lakes simulate levels 0.2 to 2.5 m lower. Human adaptation to such changes is expensive. Warmer climates would decrease the spatial extent of ice cover on the Great Lakes; small lakes, especially to the south, would no longer freeze over every year. Temperature simulations for stratified lakes are 1-7°C warmer for surface waters, and 6°C cooler to 8°C warmer for deep waters. Thermocline depth would change (4 m shallower to 3.5 m deeper) with warmer climates alone; deepening owing to increases in light penetration would occur with reduced input of dissolved organic carbon (DOC) from dryer catchments. Dissolved oxygen would decrease below the thermocline. These physical changes would in turn affect the phytoplankton, zooplankton, benthos and fishes. Annual phytoplankton production may increase but many complex reactions of the phytoplankton community to altered temperatures, thermocline depths, light penetrations and nutrient inputs would be expected. Zooplankton biomass would increase, but, again, many complex interactions are expected. Generally, the thermal habitat for warm-, cool- and even cold-water fishes would increase in size in deep stratified lakes, but would decrease in shallow unstratified lakes and in streams. Less dissolved oxygen below the thermocline of lakes would further degrade stratified lakes for cold water fishes. Growth and production would increase for fishes that are now in thermal environments cooler than their optimum but decrease for those that are at or above their optimum, provided they cannot move to a deeper or headwater thermal refuge. The zoogeographical boundary for fish species could move north by 500-600 km; invasions of warmer water fishes and extirpations of colder water fishes should increase. Aquatic ecosystems across the region do not necessarily exhibit coherent responses to climate changes and variability, even if they are in close proximity. Lakes, wetlands and streams respond differently, as do lakes of different depth or productivity. Differences in hydrology and the position in the hydrological flow system, in terrestrial vegetation and land use, in base climates and in the aquatic biota can all cause different responses. Climate change effects interact strongly with effects of other human-caused stresses such as eutrophication, acid precipitation, toxic chemicals and the spread of exotic organisms. Aquatic ecological systems in the region are sensitive to climate change and variation.

MILLER, G.S. Nearshore current and temperature measurements, western Lake Michigan. NOAA Technical Memorandum ERL GLERL-102, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB97-141691INZ) 42 pp. (1997).

Currents in the nearshore region of western Lake Michigan were characterized using measurements recorded at several mooring sites near Milwaukee Harbor, Lake Michigan during 1993-94. The observational array consisted of one mooring 7 km offshore in 23 m water that recorded current velocity and water temperature data for 450 consecutive days, two current meter moorings near the City of Milwaukee water intakes during summers in 1993 and 1994, and an additional mooring 10 km offshore during the 1994 summer. Meteorological and water temperature data were recorded on a National Data Buoy Center (NDBC) meteorological buoy moored 6 km offshore during the 1993 and 1994 open-water months. Current patterns were strongly dependent on wind direction and speed during all seasons with the most effective winds corresponding to directions with the greatest fetch. Flow was generally constrained to shore-parallel directions interspersed by periods of very weak currents. Variability during summer stratification was generated by near-inertial baroclinic internal oscillations (Poincare'-type waves) superimposed on a quasi-steady barotropic current. Maximal current magnitudes were generally less than 30 cms-1. Upwelling and downwelling events, a consequence of alongshore wind stress, were a regular feature, though the intensity was less than that generally observed on the eastern shore of Lake Michigan. Limited cross-shore transport was associated with the rotary, near-inertial, currents and the upwelling/downwelling activity during spring and summer when the lake was well stratified. Water temperatures cooled to 4oC by mid-December, decreased to near zero from mid-January to mid-March, and warmed to 4oC by mid-April. Flow was southward during the isothermal months of December through June, with limited variability at subinertial (>2-day) time scales. Current magnitudes were markedly reduced when ice cover was present in the region. Cross-shore transport at the measurement sites off Milwaukee was minimal when the water mass was vertically homogenous as indicated by the lack of onshore-offshore flow. In winter, any cross-shore transport that occurred was primarily associated with flow over bathymetric features and the coastline geometry.

Mortsch, L.D., and F.H. QUINN. Climate change scenarios for Great Lakes basin ecosystem studies. Limnology and Oceanography 41(5):903-911 (1996).

Significant change in global climate could occur due to human-induced changes in the chemistry of the atmosphere. We provide a basis for the continuing assessment of potential impacts of climate change on aquatic ecosystems. A series of climate change scenarios have been developed for the Great Lakes Basin using general circulation models (GCMs), climate spatial transpositions, and historical climate analogs. The direct impacts of climate change on the Great Lakes ecosystem would occur through higher air and water temperatures. Indirect climate change impacts include both positive and negative changes in precipitation, decreases riverine runoff, less snowfall and snowpack accumulation, higher evapotranspiration, and a reduction in lake levels and connecting channel flows. These climate and hydrologic changes affect the quantity and quality of wetland and aquatic habitats, alter the frequency and timing of lake turnover, and change dissolved oxygen, and alter fish community composition and dynamics. We provide an integration of Great Lakes climate scenarios. We also illustrate, for the first time, the spatial variability of the climate change scenarios on a tributary river-basin scale.

Schertzer, W.M., and T.E. CROLEY. Climate change impact on hydrology and lake thermal structure. Proceedings, Environmental and Coastal Hydraulics: Protecting the Aquatic Environment, Vol. 2, San Francisco, CA, August 10-15, 1997. ASCE, New York, 919-924 (1997).

The impact of climate warming on basin hydrology and lake responses is examined for the Great Lakes region and also considered for other climatic areas. Based on case studies which considered observations, steady-state and transient GCM scenarios, transposition climates, and responses of lakes in a range of climatic zones, it is demonstrated that climate warming can have significant impact on basin hydrological components and can affect thermal and stratification characteristics of lakes.

SELLINGER, C.E. Computer program for estimating evapotranspiration using the Thornthwaite Method. NOAA Technical Memorandum ERL GLERL-101, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB97-116750/XAB) 9 pp. (1996).

Understanding and estimating the earth's hydrologic cycle is important to water resource planners and managers. Evapotranspiration is one of the most difficult components of the hydrologic cycle to estimate. Thornthwaite and Mather (1955) developed a detailed method to estimate evapotranspiration. Although this method for computing potential and actual evapotranspiration is highly accepted and widely used, it is unfeasible to perform these calculations with large data sets. The computer program developed in this report allows the calculation of these parameters to be accomplished in a more efficient and timely manner.

SELLINGER, C.E. Computer program for performing hydrograph separation using the rating curve method. NOAA Technical Memorandum ERL GLERL-100, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS # PB97-116768/XAB) 11 pp. (1996).

Understanding the earth's hydrologic cycle is important to water resource planners and managers. This report presents a computerized methodology for partitioning streamflow into overland flow or runoff, and baseflow flow. Partitioning is accomplished by creating a rating curve from groundwater elevations and discharges. This hydrograph separation method differs from other published methods in that baseflow and runoff estimates are not only based upon spatial and temporal hydrologic parameters, but also on the physical properties of the watershed.

Tseng, W.Y., W.G. Pichel, A.K. Liu, P. Clement-Colon, G.A. LESHKEVICH, S.V. Nghiem, R. Kwok, and R.R. Stone. Near Real-Time RADARSAT Data System for NOAA CoastWatch Applications. Proceedings, International Geoscience and Remote Sensing Symposium (IGARSS), Singapore, August 3-8, 1997. IEEE, (1997).

No abstract.

VAN HOOF, P.L., and C.T. Jafvert. Reductive dechlorination of chlorobenzenes in surfactant-amended sediment slurries. Environmental Toxicology and Chemistry 15(11):1914-1924 (1996).

Microbial anaerobic dechlorination of hexachlorobenzene (HCB) was examined in sediment slurries amended with two classes of nonionic surfactant, polyoxyethylene (POE) sorbitan fatty acid esters (Tweens) and POE alcohols (Brijs). The rationale for surfactant addition was to increase the bioavailability of highly sorbed organic pollutants to degrading microorganisms by enhancing their solubility. The solubility of HCB was initially enhanced via micellar partitioning; however, primary degradation of most surfactants occurred within 10 d. Dechlorination activity was significantly reduced at POE alcohol concentrations above the critical micelle concentration (cmc), with or without the occurrence of surfactant degradation. Tween 80 decreased HCB dechlorination at concentrations significantly above the cmc (1,500-5,000 mg/L). At concentrations closer to the cmc (300-1,200 mg/L), Tween 80 increased dechlorination rate constants four- to fivefold in acclimated slurries. Additions of Tween 80 at or below the cmc (3, 30, 300, and 911 mg/L) stimulated dechlorination activity in unacclimated slurries that exhibited very little activity in unamended controls. An average of 89% of HCB was dechlorinated after 90 d, compared to 20% in unamended sediments. No effect was observed for POE alcohols at these sub-cmc levels. The lack of a stimulated response for the POE alcohols suggests that Tween 80 may not be acting simply as a source of carbon or energy.

VANDERPLOEG, H.A. Zebra Mussels, Blue-Green Algal Blooms, and Other Water Quality Parameters in the Great Lakes. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (1996).

No abstract.

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