GLERL Publication Abstracts: FY 1999

Publications List Key
Capitalized names represent GLERL authors.
* = Not available from GLERL.
** = Available in GLERL Library only.

ASSEL, R. A. Chapter 6. Great Lakes Ice Cover. In Potential Climate Change Effects on Great Lakes Hydrodynamics and Water Quality, D.C.L. Lam and W.M. Schertzer, American Society of Civil Engineers, Reston, VA, pp. 6.1-6.21 (1999).

The formation of ice on the Laurentian Great Lakes of North America affects the conomies of the United States and Canada, the aquatic system of the Great Lakes and local weather and climate. The annual seasonal and spatial progression of ice formation and loss is described in general terms for all the Great Lakes and in more detail for each Great Lake (Section 6.2) including ice thickness, the different types of ice formed, and ice classification. Ice cover as a hazard for commercial navigation, hydroelectricity generation, and shore property are also discussed (Section 6.3). Evidence of the effects of the ice on the lake ecosystem is provided by several recent studies on whitefish and on under-ice ecology (Section 6.4). Climate trends in ice cover over the past century, (Section 6.5) and the potential implications of climate change on the Great Lakes ice cover regime are summarized briefly (Section 6.6). For example, preliminary results show that the average ice cover duration for the 1951-80 base period, ranging from 13 to 16 weeks for Lakes Erie and Superior, was reduced by 5 to 13 weeks under those 2 x CO2 climate scenarios.

ASSEL, R. A., J. E. Janowiak, D. C. NORTON, and C. O' Connors. Climate perspective of the 1997-98 Laurentian Great Lakes ice cover. Proceedings, 10th Symposium on Global Change Studies, 79th Annual Meeting of the American Meteorological Society, Dallas, TX, January 10-15, 1999. pp. 73-76 (1999).

No Abstract.

BEETON, A. M., and R. S. Schneider. A century of Great Lakes research at the University of Michigan. Journal of Great Lakes Research 24(3):495-517 (1998).

The University of Michigan has had a long and productive history of promoting, enhancing, and facilitating research on the Laurentian Great Lakes. This interest in Great Lakes research was evident before the turn of the century under the leadership of Prof. Jacob E. Reighard. Early research was primarily concerned with fish and fisheries. The emphasis on fisheries started to shift to basic limnological research after the 1920s when Prof. Paul S. Welch started a limnology course and wrote his book Limnology. His student, Prof. David C. Chandler, returned to the University in 1953 to chair the Council of the Great Lakes Research Institute, and subsequently became the Director of the Great Lakes Research Division in 1960. The emphasis was and has been on basic and applied research involving a broad spectrum of disciplines. The published contributions include biology, chemistry, geology, meteorology, paleolimnology, physical limnology, pollution, radiolimnology, and integrated studies. Among the University's many contributions to furthering Great lakes research was the origination of the Conferences on Great Lakes Research, started in 1953. Publications of the Proceedings of these Conferences provided a valuable reference to research in the 1950s and 1960s. These conferences led to the formation of the International Association for Great Lakes Research and subsequently the Journal of Great Lakes Research. The University aquired several research vessels. The earliest large vessel acquired was the Inland Seas (1960) which was replaced by the Laurentian in 1974. A research submersible was brought into Lake Michigan for evaluation by the Great lakes Research Division in 1966. At about this time Michigan Sea Grant Program was started in 1969 and the Coastal Zone Laboratory in the 1970s. More recently the Cooperative Institute for Limnology and Ecosystem Research was created in 1989 as a partnership among the University, Michigan State University, and the Great Lakes Environmental Research Laboratory of the National Oceanic and Atmospheric Administration. Much of the Great Lakes research activity at the University was realigned into several colleges and schools in the late 1980s. Great Lakes research at the University has passed through a number of reorganizations, and now exists as the Aquatic Research Programs of the University of Michigan Biological Station.

BELETSKY, D., K. K. LEE, and D. J. SCHWAB. Large Scale Circulation. In Potential Climate Change Effects on Great Lakes Hydrodynamics and Water Quality, D.C.L. Lam and W.M. Schertzer, American Society of Civil Engineers, Reston, VA, pp. 4.1-4.42 (1999).

Large-scale circulation is stronly related to the annual cycle (Sections 4.1 and 4.2). There are also other important influencing factors such as wind, water temperature and bathymetry. Short-term effects such as storm surge, surface seiche and coastal upwelling have been successfully modeled with these factors (Section 4.3). It was found that weather forecasts can be used in predicting the three dimnesional, large-scale circulation for Lake Erie on a daily basis. Long-term effects, such as seasonal and interannual patterns are more difficult to predict because of the limited input information and the lack of reliable weather or climate forecasting techniques. Some attempts at long-term modeling analysis have led to a good understanding of seasonal patterns (Section 4.4). For example, preliminary results, either using Global Circulation Models (GCM's) or data from extreme warm or cold years, showed that prolonged stratification would increase the duration and magnitudes of the density-driven current. However, more studies and data are required to confirm these results (Section 4.5).

BELETSKY, D., J. H. SAYLOR, and D. J. SCHWAB. Mean circulation in the Great Lakes. Journal of Great Lakes Research 25(1):78-93 (1999).

In this paper new maps are presented of mean circulation in the Great Lakes, employing long-term current observations from about 100 Great Lakes moorings during the 1960s to 1980s. Knowledge of the mean circulation in the Great Lakes is important for ecological and management issues because it provides an indication of transport pathways of nutirents and contaminants on longer time scales. Based on the availability of data, summer circulation patterns in all of the Great Lakes, winter circulation patterns in all of the Great Lakes except Lake Superior, and annual circulation pattersn in Lakes Erie, Michigan, and Ontario were derived. Winter currents are generally stronger than summer currents, and therefore, annual circulation closely resembles winter circulation. Circulation patterns tend to by cyclonic (counterclockwise) in the larger lakes (Lake Huron, Lake Michigan, and Lake Superior) with increased cyclonic circulation in winter. In the smaller lakes (Lake Erie and Lake Ontario), winter circulation is characterized by a two-gyre circulation pattern. Summer circulation in the smaller lakes is different; predominantly cyclonic in Lake Ontario and anticyclonic in Lake Erie.

BUNDY, M. H., T. F. Gross, H. A. VANDERPLOEG, and J. R. Strickler. Perception of inert particles by calanoid copepods: Behavioral observations and a numerical model. Journal of Plankton Research 20(11):2129-2152 (1998).

High-resolution video showed freely swimming Diaptomus sicilis attacking and capturing inert 50 µm polystyren beads that were outside the influence of the copepod feeding current. The beads were frequently more than half a body length away and were attacked after the 'bow wake' of the moving copepod displaced the bead away from the copepod. To investigate the hypothesis that deformation of streamlines around the copepod and its first antennae stimulated the attack response, a finite element numerical model was constructed. The model described the fluid interactions between a large object approaching a smaller object in a laminar flow at Reynolds number 5, which is characteristic of the fluid regime experienced by foraging copepods. The model revealed that fluid velocity fluctuations and streamline deformations arose in the region between the two objects as separation distance between the objects decreased. The video observations and the model results support the hypotheses that chemoreception is not required for the detection and capture of large phytoplankton cells [Vanderploeg et al., in Hughes, R.N. (ed.), Behavioral Mechanisms of Food Selection, NATO ASI Series G20, 1990; DeMott and Watson, J. Plankton Res., 13, 1203-1222, 1991], and that swimming behavior plays an integral role in prey detection.

CAVALETTO, J. F., and W. S. GARDNER. Seasonal dynamics of lipids in freshwater benthic invertebrates. In Lipids in Freshwater Ecosystems, M. Arts and B. Wainman, Springer-Verlag New York, Inc., New York, pp. 109-131 (1998).

No Abstract.

CLITES, A. H., and D. H. LEE. MIDLAKES: A coordinated hydrologic response model for the middle Great Lakes. NOAA Technical Memorandum ERL GLERL-109, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 48 pp. (1998).

A new model for simulating quarter-monthly lake levels and connecting channel flows for the middle Great Lakes (Lakes Michigan, Huron, St. Clair, and Erie) has been developed under the auspices of the Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data. The new middle lakes model, MIDLAKES, is part of a larger project to develop a common American and Canadian Great Lakes regulation and routing model for both operational and research purposes. MIDLAKES is the first step in the development of the coordinated model and is expected to evolve as it is incorporated with Lakes Superior and Ontario regulation and routing modules. MIDLAKES incorporates several improvements over existing models. It utilizes a state-of-the-art finite difference solution, is programmed in modules, and is fully documented. The new model is independent of datum, units, and connecting channel stage-discharge relationships. The result is a versatile model which will be useful for operational regulation and forecasting, evaluation of alternative lake regulation plans, simulation of historical conditions, and assessment of impacts due to channel changes, diversions, and climate change. The increased availability and improved documentation of the new model may also make it useful as an educational tool. MIDLAKES was verified by comparing its computed 1900-1989 monthly mean levels and outflows to those of the Basis of Comparison prepared for the International Joint Commission’s Levels Reference Study. The annual mean difference between MIDLAKES and BOC values was -0.2 cm for levels for each lake and -3 to -4 m3/s for outflows. Model results were also compared to recorded levels and flows for the period 1974-1989. The annual mean difference between modeled and recorded values ranged from 0.6 to 1.9 cm for levels and -7 to 4 m3/s for outflows. The model was also tested using transposed climate and 2xCO2 climate scenarios and was found to be numerically robust for extreme water supply conditions. The model was evaluated for mass conservation. Mass loss or gain over a 90-year simulation period, as a percentage of mean lake outflows, was 0.4%, 5.7%, and 0.7% for Lakes Michigan-Huron, Lake St. Clair and Lake Erie, respectively.

EADIE, B. J., and S. Lozano. Grain size distribution of the surface sediments collected during the Lake Michigan Mass Balance and Environmental Mapping and Assessment Programs. NOAA Technical Memorandum ERL GLERL-111, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, (NTIS# PB99-144966/XAB) 43 pp. (1999).

The Lake Michigan Mass Balance (LMMB) study, a national demonstration program within EPA, was initiated to develop improved strategies for management and control of toxic chemicals in the coastal environment. The program included measurement and modeling of the transport, fate, and bioaccumulation of four chemicals in Lake Michigan: PCB’s (industrial compounds once widely used in a variety of products, banned since 1982), trans-nonachlor (a chlorinated hydrocarbon originally registered as a pesticide in 1948, banned by EPA in 1988), atrazine (the most widely used herbicide in U.S. corn and sorghum production), and mercury (a toxic element which occurs both naturally and anthropogenically). Over 80% of the inventories of PCBs, TNC, and mercury in Lake Michigan are stored in the sediments. Current estimates are that more of these compounds re-enter the water column via sediment-water exchange than via all of the combined external inputs.

Evans, M. S., B. J. EADIE, and R. M. Glover. Sediment trap studies in southeastern Lake Michigan: fecal pellet express or the more traveled route? Journal of Great Lakes Research 24(3):555-568 (1998).

This study investigated the composition of particulate matter in a series of sediment traps set in the offshore waters of southeastern Lake Michigan, April to October 1982. Of particular interest was the role of zooplankton fecal pellets in rapidly transporting matter from the euphotic zone to lake sediments. Particulate flux was examined microscopically. Dry weight and settling velocities were then estimated based on literature conversion factors and predictive equations. There was an excellent correspondence between estimate flux and direct measurements of flux. Flux was dominated by biological particles of autochthonous origin: fecal matter, fecal pellets, organic aggregates, phytoplankton, and zooplankton exoskeletons. Particles were small with slow (generally < 10m/day) settling velocities. Flux varied seasonally, being highest in spring and autumn, during vertical mixing, and lowest in mid-summer, during strong thermal stratification. High trapping rates during isothermal conditions previously have been associated with resuspension. However, free minerals were a relatively small component of flux. This sugests that isothermal events are associated with the resuspension of previously-settled mineral particles with these particles and slowly-settling biological particles being kept in suspension until the onset of thermal stratification. Because zooplankton fecal pellets and fecal matter are subject to significant degradation and reingestion during the days to weeks that are required for them to reach the lake floor, these egestion products may play a greater role in the recycling of matter in the water column than in the direct transport of matter to the sediment. During summer, when the abundant zooplankton population is food-limited and cladocerans, which produce diffuse egestion products are numerous, relatively little of material produced in the epilimnion settles immediately to the lake floor.

FAHNENSTIEL, G. L., A. E. KRAUSE, M. J. MCCORMICK, H. J. Carrick, and C. L. Schelske. The structure of the planktonic food-web in the St. Lawrence Great Lakes. Journal of Great Lakes Research 24(3):531-554 (1998).

The structure of the planktonic food-web was studied during the spring (April/May) and summer (August) periods in 1993 to 1995 at twelve stations located in the offshore region of all five Great Lakes. All components of the plankonic food-web were collected from the same water sample (with the exception of crustaceans), counted microscopically, coverted to carbon units, and averaged over the euphotic zone. Due to phosphorus load reductions and the impact of non-indigenous mussles in the lower lakes, physical/chemical characteristic of the lower lakes are becoming similar to those in the upper lakes. Spring total phosphorus and euphotic zone depth were relatively similar among all the stations (except western Lake Erie), ranging from 3 to 7 µg/L and 21 to 26 m, respectively. During the summer, total phosphorus concentrations were more variable, but ranged between 4 to 10 µg/L at all stations except western Lake Erie. Planktonic biomass was correlated with total phosphorus concentration. Within a season, the structure of the planktonic food-web was remarkable similar among all stations across all the lakes. Of the seventten food-web structure parameters eamined, only two exhibited significat differences among stations druing the spring isothermal period; only four parameters exhibited significant differences among stations during the summer. Small plankton were very abundant in all the lakes. Picoplankton (0.2 to 2.0µm) biomass was approximately equal to the combined biomass of nanno- and microplankton (2 to 200 µm). For microorganisms (all organisms except crsutaceans) autotrophic: hereterotrophic ratios averaged 1.3 (spring= 1.1, summer= 1.5). The heterotrophic microorganism community was comprised of bacteria (mean 65%), protozoans (mean=32%), and rotifers (3%). Even though zebra mussel veligers were found in all the lakes except Lake Superior, their contribution to microorganism biomass never exceeded 1%. Due to seasonal variation in crustacean abundance, the mean contribution of major functional groups varied by season; producers (autotrophs), decomposers (bacteria), micrograzers (protozoans and rotifers), and mesograzers (crustaceans) constituted 40%, 30%, 11%, and 19% of total planktonic carbon, respectively, during the spring, and 32%, 15%, 9%, and 43%, respectively, during the summer. The overall similarity in the structure of the planktonic food-web across all stations in the Great Lakes was attributed to the strong influence of abiotic factors.

Fisher, S. W., S. W. Chordas, and P. F. LANDRUM. Lethal and sublethal body residues for PCB intoxication in the oligochaete, Lumbriculus variegatus. Aquatic Toxicology 45:115-126 (1999).

The oligochaete, Lumbriculus variegatus, was used to examine the utility of critical body residues in describing lethal and sublethal chronic endpoints during polychlorinated biphenyls (PCB) exposure. L. variegatus was exposed to four 14C-PCB congeners and 2,2-bis-(p-chlorophyenyl)-1,1-dichloroethylene (DDE) on algal cells. Accumulation and resulting effects were monitored in 10-day acute and 35-day chronic exposures. L. variegatus was resistant to the acute lethal narcotic effects of these contaminants and no mortality was obtained in 10-day exposures. However, mortality that was significantly different from unexposed controls occurred for four compounds in 35-day assays; average body residues for chronic mortality were consistent among contaminants (0.88-1.35 mmol kg-1). Kinetic studies showed that failure to generate mortality in some exposures was due to rapid elimination. Mono-2-chlorobiphenyl, for instance, had a Kd of 0.22 h-1 which was seven to 44 times faster than for the other contaminants. Sublethal reductions in body mass and reproduction occurred at lower body residues than were needed to produce mortality (0.34 - 0.56 mmol kg-1). The consistency of the sublethal data suggests that they may offer a means of interpreting residue data for PCBs in the environment.

Fisher, S. W., H. Hwang, M. Atanasoff, and P. F. LANDRUM. Lethal body residues for Pentachlorophenol in zebra mussels (Dreissena polymorpha) under varying conditions of temperature and pH. Ecotoxicology and Environmental Safety 43:274-283 (1999).

Pentachlorophenol (PCP) toxicity was measured in the zebra mussel under varying conditions of pH (6.5, 7.5, or 8.5) and temperature (10, 17, or 25oC). Toxicity decreased significantly with increasing pH at all temperatures. At a given pH level, toxicity increased significantly with increasing temperature. PCP was most toxic at pH 6.5, 25oC and least toxic at pH 8.5. 10oC. Toxicokinetic parameters were determined at trace PCP concentrations under each combination of pH and temperature. Increasing temperature generally increased the PCP uptake clearance (ku) although elimination rate constants (kd) were unaffected. The effect of pH on toxicokinetic parameters was inconsistent but ku tended to decrease as pH and ionization of PCP increased. Lethal body residues (LR50s), estimated from kinetic parameters determined at trace PCP concentrations and the LC50 values, varied by a factor of 122 as a function of environmental conditions while LC50s varied by a factor of 381. LR50s were also estimated from the measured PCP tissue concentrations and varied by a factor of 8 across conditions. Calculated LR50s were always higher than measured LR50s determined under identical cooditions, by at least a factor of five. However, when LR50s values were recalculated using kU values measured at the LC25 concentration, the resulting adjusted LR50s varied only by a factor of 2.5 across the range of conditions studied and were more consistent with measured LR50s values. Thus, variance in the PCP concentration required to produce toxicity is reduced when LR50s are used in place of LC50s. Further, the method by which lethal residues (LR50s values) are determined can significantly affect the results and their interpretation.

GARDNER, W. S., J. F. CAVALETTO, H. A. BOOTSMA, P. J. LAVRENTYEV, and F. Troncone. Nitrogen cycling rates and light effects in tropical Lake Maracaibo, Venezuela. Limnology and Oceanography 43(8):1814-1825 (1998).

Isotope dilution experiments with 15NH+4 were conducted in Lake Maracaibo, Venezuela, to examine potential N turnover rates and light effects and to examine potential N turnover rates and light effects and to examine the hypothesis that nutrient dynamics are biologically driven in this tropical, hypereutrophic lake. Ammonium and nitrate concentrations were both <1 µM as compared to particulate N concentrations of 9-29 µM N. Chlorophyll (Chl) levels ranged from 2.5 to 22 µg liter-1. Numbers and biomass of bacteria ranged from 1.0 to 9.1 x 106 cells ml-1 and 45 to 138 µg C liter-1 and those of heterotrophic nanoflagellates (HNAN) ranged from 0.5 to 3.5 x 103 cells ml-1 and 2.3 to 17.5 µg C liter-1, respectively. Highest Chl concentration and microbial abundance occurred in a region affected by sewage discharge from the city of Maracaibo. Potential ammonium uptake rates in near-surface waters ranged from about 1 µM h-1 to 8 µM h-1. Chl-specific uptake rates were highest in central regions that were dominated by chroococcoid cyanobacteria. Ammonium regeneration rates ranged from near detection to 2 µM h-1 and correlated significantly with the ratio of HNAN to bacterial biomass, likely reflecting the degree of bacterivory. The high ratio of potental turnover rates to ambient ammonium concentrations suggests that internal recycling is a major nutrient supply process in the lake. Incubation bottle characteristics (e.g., light intensity, spectral quality, or possibly headspace differences) apparently affected potential uptake rates, which were relatively low in polystyrene bottles and in quartz tubes. Uptake rates were lower in screened polystyrene bottles than in screened polyprolpylene syringes, with difference spectral characteristcs, even though total light attentuation was similar (45% vs. 53%).

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Waterborne Contaminants in the Great Lakes. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (1999).

No abstract.

Haro, A., J. K. HORNE, D. Degan, B. Kulik, and J. Boubee. An investigation of the feasibility of employing hydroacoustic monitoring as a means to detect the presence and movement of large, adult eeels (Genus Angiulla). CARFC Internal Report 99-01, CARFC, Turners Falls, MA, 43 pp. (1999).

The management and conservation of world wide eel populations has become an issue of heightened concern in recent years, especially in North America, Europe, Asia and New Zealand. In the U.S., concerns have been raised regarding a sign)flcant increase in commercial harvest throughout most of the species' North American range, and a growing perception that recruitment to the flshery is declining at least in some river basins. Although the extent of, and causes for, this apparent decline are not documented, in recent years there has thus been growing concern among resource management agencies that greater measures must be taken to conserve remaining eel resources (ASMFC, in prep.). Fishery managers have expressed concern over potential human impacts, including mortality due to commercial over-exploitation, pollution, habitat destruction, and upstream and downstream passage at dams.

HORNE, J. K. Book Review: Animal Groups in Three Dimensions. Journal of Fish Biology 54(6):1343-1344 (1999).

No abstract.

HORNE, J. K., and J. M. JECH. Multi-frequency estimates of fish abundance: constraints of rather high frequencies. ICES Journal of Marine Science 56:184-199 (1999).

Traditional scientific echosounders operate at discrete frequencies ranging from 38 to 420 kHz. We investigated the applicability and accuracy of length-based population estimates using commercially available acoustic frequencies and the inverse approach under ideal conditions. The inverse approach combines modelled and measured backscatter values to estimate the abundance of organisms in specified length classes. Reference backscatter values of individual fish were calculated using a Kirchhoff-ray mode backscatter model. Single and multi-cohort fish populations were simulated based on length-frequency samples from purse seine catches of threadfin shad (Dorosoma petenense) and used to calculate the total frequency-dependent volume backscatter of each population. A non-negative least squares (NNLS) algorithm was used to estimate total abundance and numbers of fish in each length class. Total abundance estimates were within < I-38% of population numbers. Within length-class estimates were inconsistent among frequency combinations and across length-class criteria. Increasing the number of frequencies does not guarantee improved accuracy of within length-class abundance estimates. Predictability of inverse simulations is non-linear when rather high frequencies are combined with non-monotonic scattering models. Accuracy of length-based abundance estimates is optimized by maximizing the amplitude range of reference backscatter measures and the number of features identified by reference scattering points.

Houde, E. D., S. Jukic-Peladic, and S. B. BRANDT. Fisheries: Trends in Catches, Abundance and Management. In Ecosystems at the Land-Sea Margin, T. Malone et al. (eds.), 341-366 (1999).

Fishenes ofthe Chesapeake Bay (CB) and Northern Adnatic Sea (NA) are reviewed and compared with respect to constituents ofthe catch, trends, and management issues. Recent nnnual landings have been approximately 100,000 and 275,000 tons in the NA and CB, respectively. Clupeoid fishes (anchovies, sardines or menhaden) dominate the fish biomasses and catches in both ecosystems. Fishenes on anadromous and estuarine dependent species are more important in CB, and diverse, demersal fisheries are relatively more important in NA. Although total catches have remained high, anchovy stocks in the NA collapsed in the 1980s, and oysters and shad/ever herring stocks in CB declined to collapses dunug the past three decades. Eutrophication, overfishing, and problems of interjurisdictional management are common to the two ecosystems. The co-management of commercial and recreational fisheries is an issue in CB. Fish productivity and catches are higher in CB than in the NA on a per unit volume, area, and nutrient input basis. Yield per unit of prunary production is slightly higher in the NA. A part of the difference between the two systems is accounted for by the dominance of landings and production of menhaden, a phytoplanktivore, from Chesapeake Bay. Recent progress in development of national and international management accords (Slovenia, Croatia, Italy) is evident in the NA, and interstate plans are now required in the CB. In both systems, prospects for continued high fisheries productivity depend upon effective ecosystem and fisheries management.

Jeremiason, J. D., S. J. Eisenreich, J. E. Baker, and B. J. EADIE. PCB decline in settling particles and benthic recycling of PCBs and PAHs in Lake Superior. Environmental Science and Technology 32:3249-3256 (1998).

Sediment traps were deployed at five sites in Lake Superior at multiple depths during lake stratification in 1987 and 1991. Mass, organic carbon, PCB, and PAH fluxes were determined. PCB concentrations on settling solids declined from 1984 to 1991 with a first-order rate constant of 0.26 yr-1, similar to reported water column concentration decreases (0.20 yr-l). Total PCB settling fluxes from the upper 35 m of water averaged 121 ± 40 ng/m2 d in 1987 and 48 ± 23 ng/m2 d in 1991. Settling fluxes are greaterthan reported wet and dry deposition fluxes 12.8 ng/m2 d) and demonstrate the intense recycling of PCBs within the lake. A large fraction (>50%) of the total Lake Superior water PCB burden is transported each year by settling particles to within 5 m of the lake bottom, but om'y 2-5%.of settling PCBs accumulate in bottom sediments. Thus, most of the PCBs are recycled in the benthic region, possibly representing a major entry point for PCBs into higher trophic levels through the benthic food web. Benthic recycling of PAH compounds with three and four rings occurred, but a larger fraction of these settling PAHs accumulated in bottom sediments l8 - 33%). No consistent temporal trends were observed in PAH concentrations on settling particles from 1984 to 1991.

Kelley, J. G. W., J. S. Hobgood, K. W. Bedford, and D. J. SCHWAB. Generation of three-dimensional lake model forecasts for Lake Erie. Weather and Forecasting September:659-687 (1998).

A one-way coupled atmospheric-lake modeling system was developed to generate short-term, mesoscale lake circulation, water level, and temperature forecasts for Lake Erie. The coupled system consisted of the semi-operational versions of the Pennsylvania State University-National Center for Atmospheric Research three-dimensional, mesoscale meteorological model (MM4), and the three-dimensional lake circulation model of the Great Lakes Forecasting System (GLFS). The coupled system was tested using archived MM4 36-h forecasts for three cases during 1992 and 1993. The cases were chosen to demonstrate and evaluate the forecasts produced by the coupled system during severe lake conditions and at different stages in the Lake's annual thermal cycle. For each case, the lake model was run for 36 h using surface heat and momentum fluxes derived from MM4's hourly meterological forecasts and surface water temperatures from the lake model. Evaluations of the lake forecasts were conducted by comparing forecasts to observations and lake model hindcasts.Lake temperatures were generally predicted well by the coupled system. Below the surface, the forecasts depicted the evolution of the lake's thermal structure, although not as rapidly as in the hindcasts. The greatest shortcomings were in the predictions of peak water levels and times of occurance. The deficiences in the lake forecasts were related primarily to wind direction errors and underestimation of surface wind speeds by the atmospheric model.The three cases demonstrated both the potential and limitations of daily high-resolution lake forecasts for the Great Lakes. Twice daily or more frequent lake forecasts are now feasible for Lake Erie wth the operational implementation of mesoscale atmospheric models such as the U.S. National Weather Service's Eta Model and Rapid Update Cycle.

Kerfoot, W.C., and J.A. ROBBINS. Nearshore regions of Lake Superior: Multi-element signatures of mining discharges and a test of Pb-210 deposition under conditions of variable sediment mass flux. Journal of Great Lakes Research 25(4):697-720 (1999).

Around the turn-of-the century, mining activities greatly increased sediment accumulation and metal fluxes in nearshore regions of Lake Superior. In the low-energy environment of Portage Lake, within the Keweenaw Waterway estuary, sediment accumulation increased 33X, whereas elemental Cu flux increased 312X. One difficulty in establishing the dispersion of mining discharges is that stamp sands were derived from local ore deposits, hence few elements are “unique” to the source materials. One approach is to search for multi-elemental “signatures” in concentration and flux profiles. For example, several rare earth elements of the lanthanide series are characteristic of source materials and have the potential to identify stamp sand material across Lake Superior. Although conditions of variable mass loading from multiple sources can produce complicating dilution effects in concentration profiles, multivariate techniques are capable of deciphering original source signals. Here non-destructive neutron activation analysis was utilized to construct elemental flux and concentration profiles, then multivariate techniques (Factor Analysis, End-member Analysis) were used to illustrate how partial mass flux signatures can be assigned to two different types of ore lodes (conglomerate, amygdaloid) and to background (erosional) sedimentation. Temporal patterns were verified through archived company discharge records. Also exploited were the varve-like deposition of slime clays to independently check 210Pb determinations under conditions of variable sediment mass flux and to demonstrate constant excess 210Pb delivery to sediments in the presence of massive slime clay loading. The results suggest assumptions of 210Pb dating may apply under conditions where sediment accumulation is highly variable.

Kerfoot, W.D., C. harting, R. Rossmann, and J.A. ROBBINS. Anthropogenic copper inventories and mercury profiles from Lake Superior: Evidence for mining impacts. Journal of Great Lakes Research 25(4):663-682 (1999).

During the past 150 years. The mining industry discharged more than a billion tons of tailings along Lake Superior shorelines and constructed numerous smelters in the watershed. Given the vast size of Lake Superior, were sediment profiles at locations far offshore impacted by nearshore activities? Did copper and associated precious metal mining modify regional fluxes for copper and mercury? Samples from thirty sediment cores document that background concentrations of copper are high (mean 60.+- due to the proximity of natural ore sources. Anthropogenic inventories uncorrected for focusing also are high. ranging from 20 to 780 .ug/cm2 (mean 187 +-54 .ug/cm2 ). F ocusing factor correc- tions decrease the mean estimate and reduce variance (144 +- 24 .ug/cm2 ). Several approaches to estimating inputs suggest that only 6 to 10% of historic copper deposition originated directly from atmospheric sources, emphasizing terrestrial sources. Moreover, coastal sediment cores often show synchronous early increases in copper and mercury with buried maxima. Around the Keweenaw Peninsula, twenty-two cores trace high copper and mercury inventories back to mill and smelting sources. Direct assays of ores from thirteen mine sites confirm a natural amalgam source of mercury in the stamp mill discharges. Core records from inland lakes (Michigamme Project) also reveal patterns of copper and mercury inputs from a variety of mining sources: historic tailing inputs, amalgam assay releases, and atmospheric smelter plumes.

Kerfoot, W. C., J. A. ROBBINS, and L. J. Weider. A new approach to historical reconstruction: Combining descriptive and experimental paleolimnology. Limnology and Oceanography 44(5):1232-1247 (1999).

Here we introduce a combined expenmental and descriptive approach (termed resurrection ecology) to reconstructing historical perturbations, pointing out how direct tests with sediments and hatched resting eggs complement the traditional descriptive calculation of microfossil fluxes. In the Keweenaw Waterway, a freshwater estuary off Lake Superior, turn-of-the-century copper mining impacted the resident biota. Remain fluxes document that diatom, rhizopod, and Bosmina production all declined during stamp sand discharges but recovered rapidly after World War II, moving above background levels due to developing eutrophication. In addition to biogenic silica, we discovered that bromine flux holds promise as an indicator of diatom production and confirmed that this element is present in several genera. Fluxes of Daphnia resting eggs also increased dramatically since the 1940s, dominated by a hybrid apparently produced from crosses between offshore and interior Waterway species, after channeling promoted greater mixing of water masses. Toxicity studies with sediments and Daphnia clones directly tested recovery of environments after cessation of mining activities. The studies document that increased concentrations and fluxes of copper in the Waterway during mining discharges were toxic to invertebrates. Once stamp sand discharges ceased, the biota recovered rapidly due to a combination of decreased copper cycling and organic complexation. Although sedimentation has returned to near-background conditions and surficial sediments in much of Portage Lake are no longer toxic, eutrophication and faunal exchange with Lake Superior make it unlikely that the onginal zooplankton community composition will return to the Waterway system.

Kryza, J., and F. H. QUINN. Large Lakes Groundwater Budget. Final Report on the Bi-National Polish/U.S. Project on Comparative Groundwater Mass Water Balance Study between U.S. Great Lakes (Michigan) and Large Lake in Poland. University of Wroclaw, Laboratory of Environmental Geology, University of Wroclaw, Wroclaw, Poland, 41 pp. (1999).

The 4 year Polish-American project of estimation of groundwater inflow to lakes has come an end. It was financed by Maria Sklodowska-Curie II Found. and has furfilled most of tasks planned. The work realized with help of the Found. mentioned above consisted mainly in purchase and installation in the both centres, of necessary computer hardware, as well as, in collection and processing of hydrogeological data for investigations areas of Lake Michigan in the U.S. and lakes Zarnowiec, Goldapiwo, and Mietkow in Poland. Both national research teams visited areas under study in the U. S. and in Poland. During mutual visits work schedules and research methods were discused and test field measurements and computer simulations were carried out.Main numerical models were developed for the pilot study area in state Michigan, for Mietkow Lake and Puck Bay. For these purposes, " ModQow Model" and "Flowpath" numerical programs were used, developed by U. S. Geological Survey and modified by several University explorers. During the four-and-a-half-year period of the project we were not able to realize following plan, due to insufficient funding:
1) Broadening of models from the pilot basin onto the whole Michigan Lake.
2) Broadening of models from the pilot area of Mietkow Lake and Puck Bay onto the whole Batic CoaslineBelt and Polish Mazurian Lakes.
3) Comparative analysis of Polish and American lakes has not been finished.
Groundwater simulations done for most objects have a preliminary character. A positive result of the project is a complex preparation of the Polish centre to model studies and education of students in the field of groundwater interaction with water bodies. Papers, both published and prepared forpublishing, as well as, the monograph will supplement the report on research cooperation. The results and monograph are bringing an interesting development in the new category of hydrogeological studies. They may be of interest to the international research community.

LANDRUM, P. F., and S. W. Fisher. Influence of lipids on bioaccumulation and trophic transfer of organic contaminants in aquatic organisms. In Lipids in Freshwater Ecosystems, M. Arts and B. Wainman, Springer-Verlag New York, Inc., New York, pp. 203-234 (1998).

No Abstract.

LANDRUM, P. F., and T. F. NALEPA. A review of the factors affecting the ecotoxicology of Diporeia spp. Journal of Great Lakes Research 24(4):889-904 (1998).

Based on its biomass, Diporeia spp. represents the major benthic invertebrate in offshore waters of the Great Lakes. This work reviews the recent finding of factors influencing the organism with particular focus on interpreting the potential for contaminant stress, with an emphasis on organic contaminants, and the benthic pelagic link for contaminant food web transfer. The review includes examination of the environmental features that limit the distribution and population density. The physiology of Diporeia spp., including energy storage, respiration, and nutrient elimnination, are discussed. The toxicokinetics from both aqueous and sediment exposures are reviewed, as well as both the environmental factors that influence the kinetics and the limitations to our knowledge. The interactions of the physiology and toxicokinetics are presented for interpretation of toxic responses and the sensititvity of the organism to selected contaminants. Finally, this review suggests areas where increased information is needed to improve our understanding of Diporeia toxicokinetics and toxicity in the Great Lakes environment.

LEE, D. H. Institutional and technical barriers to implementing risk-based water resources management: A case study. ASCE Water Resources Planning and Management July/August:186-193 (1999).

Implementing risk-based Great Lakes water level management and forecasting, as recommended by the International Joint Commission, would allow managers and other interests affected by fluctuating water levels to consider the side range of potential future lake levels, incorporate some of the uncertainty inherent in forecasts, and allow explicit consideration of risk. Decision making that requires knowledge of future lake levels would potentially improve, resulting in economic and environmental benefits. Significant institutional and technical barriers preventing implementation exist, among them the lack of International Joint Commission authority to mandate other agencies to implement its recommendations, and the lack of objective evidence that risk-based water level management is an improvement over current procedures. Strategies for overcoming these and other barriers are suggested. The barriers and strategies specific to this case study are generalized so that other water resource managers may consider them with applying risk-based management to their systems.

LEE, D. H., F. H. QUINN, and A. H. CLITES. Effect of the Niagara River Chippawa Grass Island Pool on water levels of Lakes Erie, St. Clair, and Michigan-Huron. Journal of Great Lakes Research 24(4):936-948 (1998).

Because of renewed riparian interest stemming from the high Lake Erie water levels of the mid-1980s and mid-1990s and the need for a concise summary of previous studies, a review and a new assessment of the impact of the Niagara River's Chippawa Grass Island Pool on Lake Erie water levels was undertaken. Numerous field and modeling studies dating from 1953 through 1988 provided different assessments of the impacts. The impacts reported by the studies range from "no measureable effect" to a 2 to 5 cm Lake Erie water level decrease. The different results are due to different methods and data, and the fact that the impacts are not directly measureable. A new Great Lakes routing model that more accurately reflects the upper Niagara River hydraulics by explicitly considering the management directive of the Chippawa Grass Island Pool is used to estimate the impacts of deviating from the present directive. The long-term impact of a 0.30 m increase or decrease from the current directive's long-term mean pool level on lakes Erie, St. Clair, and Michigan-Huron levels is 5 cm, 4 cm, and 2 cm and -4 cm, -3 cm, and -2 cm, respectively. The lakes are minimally responsive to short-term changes in pool levels, with 50% of the Lake Erie impact achieved at about 6 months, and full impact achieved at about 2 years. The minimal lake response, the time lag to full impact, and the local problems resulting from directive deviations, make this a less favorable emergency response measure during periods of extreme lake levels than other alternatives.

LESHKEVICH, G. A., S. V. Nghiem, and R. Kwok. Great Lakes ice cover classification and mapping using satellite synthetic aperture radar (SAR) data. Proceedings, Fifth International Conference on Remote Sensing for Marine and Coastal Environments, San Diego, CA, October 5-7, 1999. ERIM, II-402 to II-405 (1999).

Owing to the size and extent of the Great Lakes and the variety of ice types and features found there, the timely and objective qualities inherent in computer processing of satellite data make it well suited for monitoring and mapping ice cover. However, during winter months cloud cover over the Great Lakes impairs the use of satellite imagery from passive sensors operating in the visible, near infrared, and thermal infrared regions and passive microwave data currently lacks the spatial resolution required for Great Lakes 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 can be developed. The European Remote-Sensing Satellite (ERS-1) SAR with vertical polarization launched in 1991 and more recently RADARSAT, an operational satellite carrying a SAR operating at 5.3 GHz (C-Band) with horizontal polarization launched in 1995, provide an opportunity for this development. Using airborne and shipborne data as "ground truth," preliminary computer analysis of ERS-1 and RADARSAT ScanSAR narrow images of the Great Lakes using a supervised (level slicing) class)fication technique indicates that different ice types in the ice cover can be identified and mapped. During the 1997 winter season, shipborne polarimetric backscatter data were acquired using the Jet Propulsion Laboratory (JPL) Cband scatterometer, together with aerial reconnaissance data, surface-based ice physical characterization measurements, and environmental parameters, concurrently with RADARSAT and ERS-2 overpass. The scatterometer data set, composed of over 20 ice types or variations measured at incident angles from 0° to 60° for all polarizations, was processed to radar cross-section and establishes a library of signatures (look-up table) for different ice types to be used in the computer ciassification of calibrated satellite SAR data. This method is used to obtain ice class)fication maps from ERS-2 SAR data.

LIU, P. C. Wind Waves on Large Lakes. In Potential Climate Change Effects on Great Lakes Hydrodynamics and Water Quality, D.C.L. Lam and W.M. Schertzer, American Society of Civil Engineers, Reston, VA, pp. 5.1-5.18 (1999).

A synopsis of the current state of knowledge on wind generated waves in the oceans and large lakes is presented. Summarized topics are focused on physical and statistical descriptions (Section 5.2), the state-of-the-art modeling of (Section 5.3) and climate effects (Section 5.4) on wind waves. As detailed understanding of the physical processes of wind waves is still elusive, large lakes like the Laurentian Great Lakes will continue to be used as an ideal proving ground for conducting and testing new conceptual advancements as well as innovations on wave analysis and prediction. For example, by relating long-term marginal probabilities of significant wave height and wind speed, condition probability parametric models can be used to offer some insight into the climatic effects on wind waves.

LOFGREN, B. M., and Y. ZHU. Seasonal climatology of surface energy fluxes on the Great Lakes. NOAA Technical Memorandum ERL GLERL-112, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, (NTIS# PB99-144958/XAB) 21 pp. (1999).

We estimate the seasonal cycle of latent, sensible, and net heat flux from the surface of the Great Lakes, using lake surface temperatures derived from the NOAA/AVHRR satellite instrument, along with meteorological data from surface station observations. Several well-known features are evident. Among these are very high outgoing fluxes of latent and sensible heat during the late fall and early winter, which drive strong cooling of the lakes, and greater seasonal variation of surface temperature and fluxes in shallower waters. Due to strong static stability of the overlying atmospheric boundary layer during the spring, both the magnitude and the spatial variation of latent and sensible heat flux are small during the spring season, and to a lesser degree the summer. The annual cycles of latent and sensible heat flux over the Great Lakes are opposite in phase to the same fluxes over land, indicating a large exchange of energy via atmospheric advection between the lake and land surfaces. A major weakness of the mehtod used here is that heat fluxes are calculated on the basis of an ice-free surface, making the derived fluxes for January through March suspect.

Lohrenz, S. E., G. L. FAHNENSTIEL, D. G. Redalje, G. A. LANG, M. J. Dagg, T. E. Whitledge, and Q. Dortch. Nutrients, irradiance, and mixing factors regulating primary production in coastal waters impacted by the Mississippi River plume. Continental Shelf Research 19:1113-1141 (1999).

Relationships among primary production, chlorophyll, nutrients, irradiance and mixing processes were examined along the salinity gradient in the Mississippi River outflow region. A series of six cruises were conducted during 1988-1992 at various times of year and stages of river discharge. Maximum values of biomass and primary production were typically observed at intermediate salinities and coincided with non-conservative decreases in nutrients along the salinity gradient. Highest values of productivity (>10 gC m-2d-l) and biomass (>30mg chlorophyll a m-3) were observed in April 1988, July-August 1990 and April-May 1992; values were lower in March and September 1991. Rates of primary production were apparently constrained by low irradiance and mixing in the more turbid, low salinity regions of the plume, and by nutrient limitation outside the plume. Highest values of primary production occurred at stations where surface nutrient concentrations exhibited large deviations from conservative mixing relationships, indicating that depletion of nutrients was related to phytoplankton uptake. Mixing and advection were important in determining the location and magnitude of primary production maxima and nutrient depletion. In addition to growth within plume surface waters, enhanced growth and/or retention of biomass may have occurred in longer residence time waters at the plume edge and/or beneath the surface plume. Vertical structure of some plume stations revealed the presence of subsurface biomass maxima in intermediate salinity water that was depleted in nutrients presumably by uptake processes. Exchange between subsurface water and the surface plume apparently contributed to the reduction in nutrients at intermediate salinities in the surface layer. DIN (= nitrate + nitrite + ammonium): PO4 (= phosphate) ratios in river water varied seasonally, with high values in winter and spring and low values in late summer and fall. Periods of high DIN: PO4 ratios in river nutrients coincided with cruises when surface nutrient concentrations and their ratios indicated a high probability for P limitation. N limitation was more likely to occur at high salinities and during late summer and fall. Evidence for Si limitation was also found, particularly in spring.

LOU, J., D. J. SCHWAB, and D. BELETSKY. Suspended sediment transport modeling in Lake Michigan. Canadian Coastal Conference 1999, Victoria, British Columbia, Canada, May 19-22, 1999. pp. 391-405 (1999).

Recent observations reveal an annual occurring major event of sediment resuspension in Lake Michigan in late winter and early spring. The sediment plume extends along the southern shore of the lake, and may significantly influence the biogeochemical processes in the coastal region. A quasi-3D suspended sediment transport model has been developed and applied to Lake Michigan to study sediment transport processes. The model was linked to a 3-D circulation model and a wind wave model. The nonlinear wave-current interaction influencing sediment transport has been taken into account in two dynamical processes: the turbulence intensity and the enhancement of the bottom shear stress. The sediment entrainment, suspension and deposition processes have been parameterized by laboratory measurement and field data. the model was calibrated with the measured sediment concentration data during a sediment resuspension episode in November-December 1994. The settling velocity, grain size, and critical shear stress have been optimized based on the measured data. In addition, the model was applied to the March 1998 Lake Michigan sediment plume event. The model results were compared with the available satellite imagery. The separate effects of waves, currents, as well as the combined effect of waves and currents on sediment resuspension and nearshore-offshore transport in Lake Michigan are investigated.

Ma, X., K. A. Bruner, S. W. Fisher, and P. F. LANDRUM. Absorption of hydrophobic contaminants from ingested Chlamydomonas rheinhardtii and Chlorella vulgaris by zebra mussels, Dreissena polymorpha. Journal of Great Lakes Research 25(2):305-317 (1999).

The zebra mussel, Dreissena polymorpha, has the potential to influence contaminant cycling in freshwater systems because of its large population density, high lipid content, and high filtering rate. Ingestion of contaminated particles such as algae dominates exposure routes for the zebra mussel for strongly particleassociated contaminants. However, the data on absorption efficiency are limited and models to predict contaminant accumulation for the lower food web have identified the absence of such data as limiting and necessary to improve predictions. Accumulation of 2,2',4,4'tetrachlorobiphenyl (TCBP), 3,3',4,4',5 pentachlorobiphenyl (PCBP), 2,2',4,4',5,5' hexachlorobiphenyl (HCBP) and 1,1 dichloro-2,2bis [4-chlorophenyl] ethylene (DDE) was determined at two algal concentrations from exposures to contaminated Chlamydomonas rheinhardtii and Chlorella vulgaris. The contaminant absorption efficiencies were determined based on a chemical mass balance model. Mussel absorption efficiencies for the four chemicals at the two different algal concentrations for the two algal species ranged from 68.3% to 95.4% and were independent of algal concentrations and algal species for the same chemical.

Manley, P. L., T. O. Manley, J. H. SAYLOR, and K. L. Hunkins. Sediment deposition and resuspension in Lake Champlain. In Lake Champlain in Transition: From Research Toward Restoration, Water Science and Application, Volume 1, T.O. Manley and P.L. Manley (eds.), Americal Geophysical Union, Washington, DC, pp. 157-181 (1999).

High-resolution side-scan sonar surveys conducted in 1991, 1994 and 1996, permitted assessment of a large furrow field located east of Valcour Island, Lake Champlain. These furrows have a width-spacing ratio of 1:4 - 1:9 which classifies them Type IA. Furrow lengths range from 16 to 828 m with over 50% of them less than 200 m. Morphological differences can be seen across the furrow field from west to east, with width-spacing ratios increasing to the west as a bathymetry becomes slightly deeper. Several mooring configurations and arrays were deployed within the furrow field including thermistor chains, sediment traps and current profilers. In addition, synoptic views from CTD/OBS surveys were obtained in 1991. The mooring in 1994 contained stereo cameras, sediment traps, thermistor chain, and an Acoustic Doppler Current Profiler (ADCP). The cameras took pictures for 23 days, at 4-hour intervals before instrument malfunction. All other apparatus operated for 4 months between June and October 1994. Correlation between the thermistor chain and the ADCP permit analysis of currents near the bottom boundary layer. Comparison of stereo images to cumnt data gives quantifiable and visible information of erosion and deposition intervals. A high-speed current event was correlated to erosion within the bottom camera area. Other high-speed events, not documented by photographs, recorded by the ADCP suggest additional erosional events within the survey region. Documentation of these erosional events indicates that furrow development occurs via high-speed internal-seiche driven cumnt activity within the bottom boundary layer separated by longer periods of deposition.

Manley, T. O., K. L. Hunkins, J. H. SAYLOR, G. S. MILLER, and P. L. Manley. Aspects of summertime and wintertime hydrodynamics of Lake Champlain. In Lake Champlain in Transition: From Research Toward Restoration, Water Science and Application, Volume 1, T.O. Manley and P.L. Manley (eds.), American Geophysical Union, Washington, DC, pp. 67-115 (1999).

Two and a half years of temperature and current observations obtained from longterm moorings within the central region of Lake Champlain were analyzed for wintertime and summertime circulation patterns. During wintertime periods, currents were consistently weaker than summertime observations. Water columns at individual sites were nearly isothermal with coldest temperatures approaching 0.5° C, however horizontal gradients were apparent. From early Spring to late Fall, the hydrodynamics of the Main Lake were dominated by the presence of a uninodal internal seiche. Spectral analysis showed the dominance of atmospherically controlled oscillations (7.1 and 10.7 days) and basin dominated modes (4.3, 2.7 and 1.8 days). A shifting of dominant periods inter- as well as intra-annually can be accounted for by varying conditions of the metalimnion as well as atmospheric forcing. The internal seiche also possessed a rotary component. Bottom currents tend to be preferentially aligned with bottom topography. Nonlinear aspects of the internal seiche in the form of internal surges and bores (gravity currents) were observed. Wave heights exceeding 10 m showed pronounced asymmetry of wave shape. Highly nonlinear events exceeding 60 m have been observed. Sudden increases in hypolimnetic temperature appear to be tied to these events. Whether these deep temperature shifts were a direct result of surface outcropping of the hypolimnion and/or sign)ficant internal mixing at the shoaling ends of the lake has yet to be determined. Near-bottom velocities of 30-50 cm/s have direct consequences for toxic sediment resuspension and dispersal.

Mason, D.M., and S.B. BRANDT. Space, time, and scale: new perspectives in fish ecology and management. Canadian Journal of Fisheries and Aquatic Sciences 56:1-3 (1999).

This supplement is the product of a special symposium organized on 'Space, time, and scale: new perspectives in fish eclogy and management' held during the 127th annual meeting of the American Fisheries Socieety in Monterey, California, August 1997. The purpose of this supplement is to illustrate the breadth and diversity of ideas and applications being explored for integrating space, time, and scaling issues and to highlight future directions. Topics cover a variety of studies, techniques, and applications from salt water to freshwater, from lotic to lenthic habitats, and across various scales that can be used as background for integrating space, time, and scale in ongoing and future fish research and management.

McCORMICK, M. J., and G. L. FAHNENSTIEL. Recent climatic trends in nearshore water temperatures in the St. Lawrence Great Lakes. Limnology and Oceanography 44(3):530-540 (1999).

In the Great Lakes region, the observational evidence for climatic change has been primarily limited to changes in lake-ice conditions,with no long-term trends identified in water temperatures. Seven nearshore water intake sites (Bay City, MI; Green Bay, WI; Sault Ste. Marie, MI; St.Joseph, MI; Sandusky Bay, OH; Put-In-Bay, OH; and Erie, PA) in the Great Lakes were chosen, and their data were examined for any climatic trends. Regression results on the annual mean temperatures showed varying support in favor of a warming trend at five of the seven sites. A new approach facilitated determination of the interannual variability in the timing of the 4oC temperature of maximum density. Two of the three sites with data records extending back to the early part of this century (Sault Ste. Marie and Put-In-Bay, respectively) showed a 4- and a 6-h yr-1 rate of increase in the maximum potential duration of summer stratification (DSS). Over the time span of these two data sets, this equates to a 14- and 18-day increase in the potential DSS, respectively. The rate of increase in the duration data was skewed, with most of the increase due to an earlier transision to springlike conditions. Finally, the data do not extend far enough back in time to know if these climatic trends are part of an unresolvable natural cycle or forced by antropogenic activity.

MCCORMICK, M. J., and D. C. L. Lam. Lake Thermodynamics. In Potential Climate Change Effects on Great Lakes Hydrodynamics and Water Quality, D.C.L. Lam and W.M. Schertzer, American Society of Civil Engineers, Reston, VA, pp. 3.1-3.20 (1999).

Vertical heat transfer is the most dominant process in lake thermodynamics, strongly affecting vertical mass and energy distributions and the lake ecosystem. Many theoretical studies (Section 3.1) on thermal structure forecasting or mixed layer (ML) modeling have used the one-dimensional approach with various formulations (Sections 3.2 and 3.6). By comparing predicted results from four ML models for three GCM scenarios (Section 3.3) it was found that the models were useful, provided that they can solve the horizontal variabilities (lakewide vs. coastal) as well as the different temporal scales (climate effects vs. natural basin oscillations). Only when such theoretical and practical considerations are made, one would look carefully into possible climate change effects. As an example, in Section 3.4, application of the Garwood Model (1977) to Lake Michigan under a potential doubling of CO2 shows pronounced changes in both the annual temperature cycle and heat content with the possibility for permanent stratification under some scenarios. This is not a climate change forecast but rather it documents the sensitivity of the lake's thermal structure to low frequency changes in the new surface heat flux that are often predicted by GCM's.

MILLER, G. S., J. H. SAYLOR, and M. J. McCORMICK. Detecting storm-generated suspended materials in Lake Michigan using ADCP echo intensities. Proceedings, IEEE Sixth Working Conference on Current Measurement, March 11-13, 1999. pp. 264-268 (1999).

Data from Acoustic Doppler Current Profilers deployed in the nearshore region of southeastern Lake Michigan provide evidence of sediment resuspension episodes and cross-shelf flux of materials during strong winter storms. Significant increases (+20 dB) in echo intensity and current velocities correlate well with satellite imagery of a sediment-laden plume transporting material in a cyclonic flow around the lake basinis perimeter. A decrease in echo intensity to near-background levels following resuspension events suggests that the larger particles settle out, leaving the very fine material that remains visible in satellite imagery for many days. Although there were no concurrent Total Suspended Material measurements during the event, the ADCP results suggest that resuspension events and plume movements can be detected.

NALEPA, T. F., D. J. HARTSON, D. L. FANSLOW, G. A. LANG, and S. J. Lozano. Declines in benthic macroinvertebrate populations in southern Lake Michigan, 1980-1993. Canadian Journal of Fisheries and Aquatic Sciences 55(11):2402-2413 (1998).

Densities of the major benthic macroinvertebrate goups declined dramatically at sites shallower than 50m in southern Lake Michigan between 1980 and 1993. Declines in Diporeia, Oligochaeta, and Sphaeriidae ranged from 40 to 75% at these depths. Total densities declined from 16 800•m-2 in 1980-1981 to 4800•m-2 in 1992-1993 at sites in the 16-30 m depth interval and from 21 300 to 11 300•m-2 at sites in the 31-50 m depth interval. Changes at sites deeper than 50 m were minimal; only sphaeriids declined to any extent. Declines in oligochaetes and sphaeriids were most likely related to reductions in phosphorus loads and a general decrease in productivity in the nearshore area over the sampling period. On the other hand, declines in Diporeia occurred mainly in the later portion of the sampling period and were greatest in the southeastern region of the lake. Densities at many sites in the southeastern region were <100•m-2 in 1993, down from 300-8000•m-2 in 1980-1987. We hypothesize that the filtering activities of large populations of Dreissena polymorpha in nearshore waters may be having a negative impact on Diporeia in deeper waters by decreasing the amount of food available to this surface-feeding detritivore.

NGHIEM, S. V., G. A. LESHKEVICH, and R. Kwok. Shipborne scatterometer measurements of Great Lakes ice. Proceedings, Fifth International Conference on Remote Sensing for Marine and Coastal Environments, San Diego, CA, October 5-7, 1998. II-406 to II-409 (1999).

The Jet Propulsion Laboratory C-band polarimetric scatterometer was used to measure radar backscatter of Great Lakes ice during the 1997 Great Lakes winter experiments. The scatterometer data are at the same frequency band, incident angles, and polarizations of operating satellite SARs such as RADARSAT and ERS or future multipolarization SARs such as ENVISAT and RADARSAT-II. During the experiments, in situ data for different ice types were obtained and accurate radar calibration measurements were conducted. We present backscatter results over the range of incident angles up to 60° for various ice types with different physical conditions, feature scale, thickness, snow cover, and concentration. The scatterometer data set is useful for the development of the Great Lakes ice mapping algorithm.

O'CONNOR, W. P., D. J. SCHWAB, and G. A. LANG. Forecast verification for Eta Model winds using Lake Erie storm surge water levels. Weather and Forecasting February 1999:119-133 (1999).

This article has two purposes. The first is to describe how the Great Lakes Coastal Forecasting System (GLCFS) can be used to validate wind forecasts for the Great Lakes using observed and forecast water levels. The second is to evaluate how well two versions (40 km and 29 km) of the numerical weather prediction step-coordinate Eta Model are able to forecast winds for the Great Lakes region, using the GLCFS as a verification technique. A brief description is given of the 40- and 29-km versions of the Eta Model and their surface wind and wind stress output. A description is given of the GLCFS for Lake Erie. This includes the numerical Princeton Ocean Model (POM), observed winds from surface meteorological stations and buoys, and water level guage data. The wind stresses obtained from both the 40-km Eta Model and the observed winds are used to force the POM for Lake Erie for several periods in 1993 when water level surges were recorded. The resulting POM water levels are then compared to observed water levels to provide an indication of the accuracy of 40-km Eta Model forecasts. The same experiments are made with the POM using wind stresses from the 29-km Eta Model and observed winds in 1997. Twin experiments are made with the GLCFS to determine: 1)how well it can predict (hindcast) water levels using observed winds as forcing, and 2) how well it can predict water levels using both the 40- and 29-km Eta Model forecast winds as forcing. The use of this forecast validation technique for other coastal forecasting systems is discussed.

Omair, M., H.A. VANDERPLOEG, D.J. Jude, and G.L. FAHNENSTIEL. First observations of tumor-like abnormalities (exophytic lesions) on Lake Michigan zooplankton. Canadian Journal of Fisheries and Aquatic Science 56:1711-1715 (1999).

Tumor-like abnormalities (exophytic lesions) were found on a variety of planktonic calanoid copepods and cladocerans (Diaptomus spp., Epischura lacustris, Limnocalanus macrurus, Polyphemus pediculus, Diaphanosoma sp., and Daphnia galeata mendotae) collected from inshore (3-m depth contour) and offshore (100- to IIO-m depth contours) stations of eastern Lake Michigan. The abnormalities, which were quite large relative to animal size and variable in shape, are documented in photographs. Abnormality incidences among species ranged between O and 72%. Predatory species of calanoids and cladocerans had higher incidences of tumors than herbivorous species. The abnormalities on some copepods were very similar to cysts described for calanoid copepods in Lago Maggiore, Italy, which like Lake Michigan is undergoing oligotrophication. The recent appearance of the lesions in Europe and North America may indicate an emerging global phenomenon that has a common cause.

QUINN, F. H. Anthropogenic changes to Great Lakes water levels. US Army Corps of Engineers, Detroit District, Great Lakes Update 136:1-4 (1999).

Most observers of Great Lakes water levels are familiar with the changes in Great Lakes water levels due to natural climate variability. These include the seasonal cycle, with the lakes peaking in the summer and falling to minimums in mid-winter, and the normal interannual variability which results in year-to-year changes including both high and low water level episodes. However, many people are not familiar with the anthropogenic or man-made changes to the system. These changes have resulted in either permanent alternation of water levels or a decreased range of levels. The former include diversions into, out of, or between the lakes, navigational dredging, sand and gravel dredging, filling, and infrastructure placed in the connecting channels. The latter includes the regulation of Lakes Superior and Ontario. While individual impacts may or may not seem significant, cumulative impacts of even small changes may be important.

QUINN, F. H. The potential impacts of climate change on Great Lakes water resources, a review. Specialty Conference on Potential Consequences of Climate Variability and Change to Water Resources on the United States, D. Briane Adams (ed.), Atlanta, GA, May 10-12 1999. American Water Resources Association, pp. 311-315 (1999).

The Great Lakes are one of North America's largest water resource systems with a basin area of about 770,000 km2, of which about one third is lake surface. It is one of the most intensively used fresh water systems inthe world, serving multiple interests including navigation, hydropower, recreation, water supply, food supply, and riparian. The outflows from Lakes Superior and Ontario are regulated by regulatory works in the St. Marys and St. Lawrence Rivers recpectively. The remainder of the system is naturally regulated through the large surface areas and limited outflow capacity. Great Lakes water levels change slowly due to the large lake surface areas and constricted outlet channels, which integrate short-term climate fluctuations. There is a likely potential for significant global climate change due to increased greenhouse gas concentrations in the atmosphere.

ROBBINS, J. A., K. R. Reddy, C. W. Holmes, N. R. MOREHEAD, M. Marot, and R. W. ROOD. Sediment core dating with 137Cs. Final Report to the South Florida Water Management District, Contract Number: C-5324. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 97 pp. (March 12, 1999).

The principal aims of this study were to date additional soil cores from the Water Conservation Areas (WCAs) in south Florida using the 137Cs method and to assess its accuracy. The method is based on the assignment of the date of maximum atmospheric fallout of 137Cs (May, 1963) to single, sub-surface peaks in soil-core radionuclide activity profiles. Cores collected from WCA-1, -2A and - 3A betweeen January 1993 and December 1996 were anayzed for 137Cs and, selectively, for 210Pb as well as numerous stable elements. Additionally, bulk samples of soil and extracted interstitial water as well as samples of surface water and the dominant species of plants (cattails and sawgrass) from WCA-2A were analyzed for 137Cs. Selected soil samples were chemically fractionated to assess the present degree of binding of 137Cs to soil solids. Also, laboratory experiments were undertaken to characterize short-term (~100 day) solid-water partitioning of the radionuclide added as a carrier-free spike to soil-water mixtures.The study has provided 22 additional 137Cs profiles, many of which have yielded estimates of mean soil accretion rates that can be used by others to calculate net rates of phosphorus accumulation on transects along vegetational/nutrient gradients in the Water Conservation Areas. The study has demonstrated a considerable within-site variability in application of the method to obtain mean post-1960 accretion rates (ca 20-30%) and considerable discrepancies between1377Cs peak age assigments, based independently on 210Pb dating, and the maximum fallout date (ca 40%). Such lack of precision and accuracy can arise from many processes discussed in this report, including specification of the soil-water interface because of topographic relief, the variable occurrence of periphyton mats, post-depositional mobility of radiocesium in the soil matrix due to both diffusional and advective processes, down-core variation in the degree of binding of the radionuclide to soil solids, system-time averaging, which can cause up to 3-year lags between the atmospheric fallout maximum date and times of maximum delivery of 137Cs to soil surfaces, and variable accumulation rate effects. The study shows that roughly 30% of the radiocesium still remains in the Water Conservation Areas and that small amounts continue to be recycled by plants 30 years after the fallout period. Although large uncertainties attend the reporting of mean accretion rates based on 137Cs dating, past uses of the method to establish order-of-magnitude changes in soil nutrient accumulation rates along vegetation/nutrient gradients in the WCAs are acceptable. In these south Florida wetlands, the degree of penetration of 137Cs is far greater than that expected from the fallout record and the horizon (penetration depth) should not be used for chronological purposes at all. In addition, the method is of dubious value in cases where peaks are less than about 3 cm from the soil-water interface. Future studies reguiring chronostratigraphic information should rely on 210Pb dating and consider 137Cs as one among several methods for validating the 210Pb method.

RODIONOV, S., and R. A. ASSEL. Laurentian Great Lakes ice cover and atmospheric teleconnection patterns: A decision-tree analysis. Proceedings, Eighth Conference on Climate Variations, Denver, CO, September 13-17, 1999. American Meteorological Society, Boston, MA, pp. pp. 38-43 (1999).

Great Lakes ice cover affects the winter lake aquatic system, winter navigation and hydropower generation, winter recreational activity, and lake effect snowfall. Many factors determine the severity of an ice season and among the most important is atmospheric circulation. Advection of warm or cold air masses and wind speed affect latent and sensible heat exchange between the atmosphere and the lakes and thus the rate of winter cooling and ice formation.

Rudstam, L., J. K. HORNE, and G. Gleischer. Translation of acoustic data to fish abundance (and standardization of acoustic methods for the Great Lakes region). Report from the Great Lakes Acoustic Workshop III, Cornell Biological Field Station, February 11-12, 1999. 12 pp. (1999).

No Abstract.

Sae-Ma, B., P. G. Meier, and P. F. LANDRUM. Effect of extended storage time on the toxicity of sediment-associated cadmium on midge larvae (Chironomus tentans). Ecotoxicology 7:133-139 (1998).

The effect of the duration of spiked sediment storage on cadmium toxicity was studied. Sediment samples were spiked with cadmium to obtain concentrations of 0.6, 16.0, 29.0, and 53.0 µg Cd per g sediment (dry weight). The spiked sediment was then stored in sealed plastic containers at 4oC in the dark. Sediment bioassays, using Chironomus tentans, were conducted immediately and at periodic intervals for up to 4 months. Though the levels of cadmium in the bulk sediment samples from different stored periods were not significantly different, different toxicity levels to C. tentans were observed. The toxicity was significantly different between subsequent storage times. There was a significant decrease in the bioaccumulation factor (BAF) values with extended storage times, indicating a reduction in the bioavailability of cadmium. This study suggests that the storage of spiked sediment used in toxicity study can influence the results.

SAYLOR, J. H., G. S. MILLER, K. Hunkins, T. O. Manley, and P. L. Manley. Gravity currents and internal bores in Lake Champlain. In Lake Champlain in Transition: From Research Toward Restoration, Water Science and Application, Volume 1, T.O. Manley and P.L. Manley (eds.), American Geophysical Union, Washington, DC, pp. 135-155 (1999).

The shape of lake basins, with a large variety of configurations, plays a strong role in determining the current and circulation patterns within them. Elongated and narrow basins such as Lake Champlain can exhibit extremely large thermocline displacements and oscillations in response to wind forcing during seasons of density stratification. Time series of currents and temperature variations in Lake Champlain were recorded during the season of thermal stratification for three consecutive years. The measurements were made using arrays of Acoustic Doppler Current Profilers and thermistor chains moored along the lake's thalweg. The long axis of the lake is oriented approximately north-south and is nearly 120 km long. The lake is about 6.3 km wide and has a mean depth of about 30 m. The depth decreases monotonically toward its north end from a maximum depth of 120 m at a locadon in the south. During seasons of weak thermal stratification in early summer and fall, strong winds from the south were observed to transport much of the less dense surface layer toward the north end of the basin and cause upwelling in the south. The resulting density distribution is similar to that observed in a lock exchange flow. A gravity current flows northward along the lake floor after the wind stress relaxes. The propagation of the current was monitored as it progressed through instrument moorings placed in the lake's shoaling north end. Evolution of the gravity currents into bore-like waves traveling on weak near bottom stratification occurred at the northemmost measurement location.

Schertzer, W. M., and T. E. CROLEY. Climate and Lake Responses. In Potential Climate Change Effects on Great Lakes Hydrodynamics and Water Quality, D.C.L. Lam and W.M. Schertzer, American Society of Civil Engineers, Reston, VA, pp. 2.1-2.74 (1999).

The study on the effects of climate on basin hydrology and lake responses, using examples primarily drawn from the Great Lakes region, is explained in three parts. Firstly, the base case 'current' climate elements are constructed from more than 30 years of records (Sections 2.1 to 2.4). Secondly the climate change case is examined through modeling studies using extreme variations in the observations, steady-state Global Circulation Model (GCM) scenarios and trasnposition climates (Section 2.4 to 2.7). When compared to the base case observations, these preliminary Great Lakes results indicate increases in evaporation, runoff reduction, and disruptions to lake thermal stratification characteristics due to climate warming. Thirdly, preliminary results from other lake systems reinforced findings determined from the Great Lakes case (Section 2.8). These results are preliminary and their interpretation requires caution, particularly on the limitations and capabilities of the models used which is discussed in subsequent chapters.

SCHWAB, D. J., and D. BELETSKY. Lake Michigan Mass Balance Study: Hydrodynamic modeling project. NOAA Technical Memorandum ERL GLERL-108, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, (NTIS# not yet available) 53 pp. (1998).

This report describes the hydrodynamic modeling framework for the U.S. EPA Lake Michigan Mass Balance Study. It consists of a three-dimensional lake circulation model, surface flux model for atmospheric input, and a wind wave model. These models provide a description of the physical environment for sediment resuspension and transport models, as well as eutrophication and toxic contaminant models. The models are validated using an extensive array of long-term measurements of temperature, currents, water levels, and wind waves in Lake Michigan during the 1982-83 calibration period and the 1994-95 Mass Balance Study period.

SCHWAB, D. J., and D. BELETSKY. Propagation of kelvin waves along irregular coastlines in finite-difference models. Advances in Water Resources 22(3):239-245 (1998).

In this paper, we examine the behavior of internal Kelvin waves on an f-plane in finite difference models using the Arakawa C-grid. The dependence of Kelvin wave phase speed on offshore grid resolution and propagation direction relative to the numerical grid is illustrated by numerical experiments for three different geometries: (1) Kelvin wave propagating along a straight coastline; (2) Kelvin wave propagating at a 45° angle to the numerical grid along a stairstep coastline with stairstep size equal to the grid spacing; (3) Kelvin wave propagating at a 45° angle to the numerical grid along a coarse resolution stairstep coastline with stairstep size greater than the grid spacing. It can be shown theoretically that the phase speed of a Kelvin wave propagating along a straight coastline on an Arakawa C-grid is equal to the analytical inviscid wave speed and is not dependent on offshore grid resolution. However, we found that finitedifference models considerably underestimate the Kelvin wave phase speed when the wave is propagating at an angle to the grid and the grid spacing is comparable with the Rossby deformation radius. In this case, the phase speed converges toward the correct value only as grid spacing decreases well below the Rossby radius. A grid spacing of one-fifth the Rossby radius was required to produce results for the stairstep boundary case comparable with the straight coast case. This effect does not appear to depend on the resolution of the coastline, but rather on the direction of wave propagation relative to the grid. This behavior is important for modeling internal Kelvin waves in realistic geometries where the Rossby radius is often comparable with the grid spacing, and the waves propagate along irregular coastlines.

SELLINGER, C. E. La Nina and the Great Lakes Region. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (1998).

No abstract.

SELLINGER, C. E., and F. H. QUINN. Proceedings of the Great Lakes Paleo-Levels Workshop: The Last 4000 Years. NOAA Technical Memorandum ERL GLERL-113. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, (NTIS# PB99-166308/XAB) 43 pp. (1999).

The Great Lakes are one of North America’s largest water resource systems with a basin area of about 770,000 km2, of which about one third is lake surface. It is one of the most intensively used freshwater systems in the world, serving multiple interests including navigation, hydropower, recreation, water supply, food supply, and riparian. The outflows from Lakes Superior and Ontario are regulated by regulatory works in the St. Marys and St. Lawrence Rivers, respectively. The remainder of the system is naturally regulated through the large surface areas and limited outflow capacity. Great Lakes water levels change slowly due to the large lake surface areas and constricted outlet channels, which integrate short-term climate fluctuations. Because of the relatively small range in lake levels, about 1.8 m, significant uses have become dependant upon small changes in water levels and outflows, resulting in system sensitivity to relatively small changes in climate variability and change. The Great lakes water levels constitute one of the longest high quality hydrometeorological data sets in North America with master gage records beginning about 1860 with other sporadic records back to the early 1800’s. However, from a longer term perspective under the current system hydraulic regime, which has been in place for about 3000 years, we have only observed/measured about 5 percent of the time series. There is a highly likely probability that we could experience runs of high and low lake levels with extremes significantly higher than our present measurements would indicate. For example, few if any envisioned in the 1960’s that we would have a 30 year run of well-above-average high lake levels and set two record highs within 13 years. A longer term lake level perspective can only be obtained by examining paleo information from the geologic record, or in a more limited fashion, from stochastic hydrologic analysis based upon the historic record.The workshop was convened to place the historical lake level measurements in a longer term perspective through a series of papers and discussion by highly qualified experts in the specialized field of Great Lakes paleo lake level reconstruction. This perspective will serve a broad range of uses from evaluation of potential Great Lakes shoreline damages to the development of more robust lake level regulation and water resource policy.

Tenzer, G. E., P. A. Meyers, J. A. ROBBINS, B. J. EADIE, N. R. MOREHEAD, and M. B. LANSING. Sedimentary organic matter record of recent environmental changes in the St. Marys River ecosystem, Michigan-Ontario border. Organic Geochemistry 30:133-146 (1999).

Lake George, located in the St. Marys River, has been heavily impacted by human-induced environmental changes over the past century. The effects of human impacts starting in the late nineteenth century and of natural, gradual diagenesis can be distinguished in the bulk organic matter and molecular contents of the sedimentary record. Organic carbon concentrations increase from 0.5% in sediments deposited 200 years ago to ~4% in recent sediments. A fourfold increase in organic carbon mass accumulation rates accompanies the change in concentrations. Elevated C/N ratios in near-modern sediments indicate that increased delivery of land-derived organic matter has been responsible for much of the recent increases in sedimentary organic carbon. Organic d13C and d15N values change significantly and cooincidentally with the environmentalchanges, reflecting depressed algal productivty since the introducation of industrial effluents to the aquatic system, increased delivery of land-derived organic matter and some impacts of acid rain. Increases in microbial and petroleum hydrocarbon contributions occur in sediments deposited since 1900. Fatty acid distributions provice evidence of substantial microbial reworking of organic matter throughout the sedimentary record.

TYLER, J. A. GRP Map Maker: A User's Guide to Spatial Models of Fish Habitat Combining Acoustic Data and Bioenergetics Models. NOAA Technical Memorandum ERL GLERL-110, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, (NTIS# PB99-114837/XAB) 51 pp. (1998).

No abstract.

ZHU, Y., and B. M. LOFGREN. Spatially distributed water surface temperature modeling for the Great Lakes. Proceedings, 14th Conference on Hydrology, Dallas, TX, January 10-15, 1999. American Meteorological Society, pp. 431-434 (1999).

A growing concern over the potential effects of a possible change in the future climate continues to motivate research into cycles, variability, and trends in the temperatures of the Great Lakes. These temperatures have a major influence on the water balance of the Great Lakes watershed through evaporation and the forcing of atmospheric effects. Before a future temperature structure and cycle can be estimated, the present water temperature climatology must be sucessfully simulated. On the other hand, evaporation estimates for the Great Lakes require water surface temperature data over long time periods. The simulation of water surface temperature has long been recognized as an important tool for lake resource management. Models with varying degrees of complexity have been generated to fill this role. GLERL developed a one-dimensional heat storage model and one-dimensional ice thermodynamic model for the Great Lakes (Croley, 1989, 1992; Croley and Assel, 1994), which provides multiple, long-period and continuous simulations for mixed-layer development, water column turnover, heat-temperature hysteresis, seasonal heating and cooling cycles, ice thickness, and ice concentration. Hostetler and Bartlein (1990) presented and validated a one-dimensional eddy diffusion model for simulating the seasonal variation in lake temperature and evaporation.

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