GLERL Publications Abstracts: FY 1977

ASSEL, R.A. Great Lakes ice thickness prediction. Journal of Great Lakes Research 2(2):248-255 (1976).

Weekly ice thickness data, collected from 24 bay, harbor, and river sites on the Great Lakes, were correlated with freezing degree-day accumulations to develop regression equations between ice thickness and freezing degree-days. The data base at ice measurement sites was 3 to 8 winters in length. The standard error of estimate varied for individual regression equations and averaged between 7 and 8 cm for five forms of regression equations. Because the regression equations are empirical, the range of input data used to predict ice thickness should be limited to the range of values used in the derivation.

ASSEL, R.A., and F.H. QUINN. Preliminary classification of Great Lakes winter severity, 1947-76. GLERL Open File Report, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (1977).

No abstract.

BENNETT, E.B., and J.H. SAYLOR. Physical limnology. In The Waters of Lake Huron and Lake Superior, Vol. III, Part B: Lake Superior, Upper Lakes Reference Group (eds.). International Joint Commission, Windsor, Ontario, Canada, 249-276 (1977).

This section discusses the characteristics of the physical limnology of Lake Superior as a whole with the objective of providing background for addressing the Reference Questions and, in particular, those relating to transboundary movement of materials in the lake. Included below are discussions of many physical processes and characteristics which do not directly influence the water quality of the lake, but, in each case, these processes are intimately connected with biochemical processes and factors bearing on water quality criteria and guidelines for Lake Superior and, hence, are relevant to this report.

BENNETT, J.R. A three-dimensional model of Lake Ontario's summer circulation. I. Comparison with observations. Journal of Physical Oceanography 7:591-601 (1977).

Observations of Lake Ontario during the International Field Year for the Great Lakes are used to develop a three-dimensional numerical model for calculating temperature and current. The model has a variable grid resolution and a horizontal smoothing which filters out small-scale vertical motion caused by truncation error but has little effect on the strong currents of the coastal boundary layer. Resolution of the shore zones and reduced horizontal smoothing improve simulation of both long-term mean flow and current reversal due to low-frequency waves.

BENNETT, J.R., and E.J. Lindstrom. A simple model of Lake Ontario's coastal boundary layer. Journal of Physical Oceanography 7(4):620-625 (1977).

An empirical forced wave model of currents and thermocline displacements in the coastal zone of Lake Ontario is derived from data from the International Field Year for the Great Lakes (1972). The model consists of three linear wave equations for predicting the depth of the thermocline, its slope and the longshore volume transport from the wind. The empirical phase speeds are consistent with internal Kelvin wave and topographic wave theory and the response to a unit longshore wind stress is consistent with cross-section models of long lakes.

BOLSENGA, S.J. The radiation balance over a continuous snow surface: A review. GLERL Open File Report, Great Lakes Environmental Research Laboratory, Ann Arbor, MI 33 pp. (1977).

A review of selected, comprehensive, and authoritative literature items pertaining to the radiation balance over a continuous snow surface is presented. Information is provided on the short-wave and long-wave fluxes, including the transmitted, absorbed, reflected, and emitted components. Measurements from a wide variety of geographical locations are described, but gaps exist, particularly with respect to the complex situation that applies to valley glaciers.

CHAPRA, S.C. Total phosphorus model for the Great Lakes. Journal of Environmental Engineering Division, ASCE 103:147-161 (1977).

No abstract.

CHAPRA, S.C., and A. ROBERTSON. Great Lakes eutrophication: The effect of point source control of total phosphorus. Science 196:1448-1450 (1977).

A mathematical model of the Great Lakes total phosphorus budgets indicates that a 1 milligram per litter effluent restriction for point sources would result in significant improvement in the trophic status of most of the system. However, because large areas of their drainage basins are devoted to agriculture or are urbanized, western Lake Erie, lower Green Bay, and Saginaw Bay may require non-point source controls to effect significant improvements in their trophic status.

CHAPRA, S.C., and S.J. TARAPCHAK. A chlorophyll a model and its relationship to phosphorus loading plots for lakes. Water Resources Research 12(6):1260-1264 (1976).

A model predicting the summer concentration of chlorophyll a in a phosphorus-limited lake is derived from simple empirical and semitheoretical relationships. The model is rearranged and expressed as a phosphorus loading plot which agrees closely with the predictions of Vollenweider's model. The model can be used to gain insight into the phosphorus loading concept. The primary conclusion is that a lake's tolerance to phosphorus loading is a function of two processes: sedimentation and flushing rate. At low areal water loads, in-lake forces which remove phosphorus to the sediments predominate. At high areal water loads, flushing of phosphorus through the lake's outlet is the factor governing eutrophication. The importance of the steady state assumption is also demonstrated by using data for Lake Washington.

Cline, J.T., and R.L. CHAMBERS. Spatial and temporal distribution of heavy metals in lake sediments near Sleeping Bear Point, Michigan. Journal of Sedimentary Petrology 47(2):716-727 (1977).

Q-mode factor and R-mode principal components analyses were used on heavy metal (Mn, Co, Cr, Cu, Zn, Cd, Ag, Ni) concentration gradients, grain size and organic carbon measurements to delineate time-spatial patterns and general principles in complex data. Three Q-mode factors account for 99.5% of the variance in 39 surface samples. Factor I accounts for 77. 1% of the total variation and is related to shallow-water samples with low metal concentrations. Factor II is associated with samples of high metal loading and profundal water; this factor accounts for 19.6% of the variance. Factor III accounts for only 2.7% of the variance and is related to samples intermediate to factors I and II. The sediment strata (i.e., slump and varve-like features) were grouped into geochemical clusters related to sediment type by Q-mode cluster analysis. R-mode principal components analysis of the chemical and physical parameters within each piston core are highly correlated (a = 0.05). Normalized heavy metal concentrations (weighted to grain size) show upward increasing metal concentrations in homogeneous slump units at depth suggestive of noncultural accumulations and metal migration. Simultaneous analysis of 10-cm surface cores show that Mn, Cd and Zn concentrations correlate the highest with depth of sediment, suggestive of upward migration and accumulation. The average metal concentrations, on a time-spatial basis, are grain size dependent (a = 0.05), but heavy metal distributions in the upper 10 cm are caused by geochemical and/or physical factors resulting in the chemical gradients. The geochemical factor accounts for 11% of the variance, while the physical factor accounts for 75% of the total variance as determined by principal component analysis.

**Cutchin, D.L., and D.B. RAO. Baroclinic and barotrophic edge waves on a continental shelf. Special Report No. 30. Department of Energetics and Center for Great Lakes Studies, the University of Wisconsin-Milwaukee, 53 pp. (1976).

No abstract.

DERECKI, J.A. Heat storage and advection in Lake Erie. Water Resources Research 12(6):1144-1150 (1976).

Heat content and net advection based on long-term monthly mean input data covering 17 yr (1952-1968) were derived for Lake Erie. The lake heat storage changes and net advection, with major components, are presented for the average monthly periods, indicating normal values for these parameters. Data limitations for the lake heat content precluded computation of monthly values by individual years. Derivation of the necessary input data (water temperature profiles, water supply and loss factors with appropriate temperatures, and ice conditions) is briefly described.

DERECKI, J.A. Lake Erie terrestrial radiation. Water Resources Research 12(5):979-984 (1976).

Terrestrial or long-wave radiation over a body of water consists of the atmospheric radiation, with incident and reflected components, and the radiation emitted by the water body. These three radiation components produce a net back radiation, an energy loss from the water to the atmosphere. Basic required data (air temperature, humidity, solar radiation, and water surface temperature) were derived, and long-term (17 years) average monthly radiation values were calculated for the Lake Erie incident and reflected atmospheric radiation and the radiation-emitted by the water body. The net result or the effective net back radiation averaged 100 Ly/d from 1952 to 1968.

EADIE, B.J., and A. ROBERTSON. An IFYGL carbon budget for Lake Ontario. Journal of Great Lakes Research 2(2):307-323 (1976).

A carbon budget was produced for each month of the International Field Year for the Great Lakes (IFYGL) year (April 1972 to March 1973) to determine the importance of the various sources and sinks of carbon. Major sources were found to be C02 which was fixed in organic matter during primary production and inorganic carbon in tributary streams, especially the Niagara River. The major sinks were found to be inorganic carbon outflow at the St. Lawrence River and net C02 gas exchange between the inorganic carbon pool and the atmosphere. Inflow and outflow of organic matter in rivers, sedimentation of organic and inorganic matter, ground water transport, and municipal and industrial perturbations accounted in total for less than 10% of the annual budget. The lake had an inventory of approximately 4.0 x 1010 kg of inorganic carbon and approximately an order of magnitude less organic carbon. The riverborne flux of inorganic carbon of 0.5 x 1010 was 13% of the lake's inventory, assuming complete mixing; a minimum mean residence time of 8 years can be calculated from that inventory. The seasonal cycle inherent in the fixation of carbon in primary production was primarily balanced by a complementary seasonal cycle in the air-lake C02 gas exchange system. The lake acts as a sink for C02 gas in the warm months when primary productivity is highest and as a source of C02 in the colder part of the year.
The IFYGL year had higher than normal rates of water flow, but this does not appear to have perturbed the inorganic carbon system. A comparison of IFYGL carbon budget results with corresponding estimates calculated for a typical year from historical data shows no major differences

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Annual Report for the Great Lakes Environmental Research Laboratory, FY 1977. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 33 pp. (1977).

No abstract.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Detailed technical plan for the Great Lakes Environmental Research Laboratory. Great Lakes Environmental Research Laboratory, Ann Arbor, MI 204 pp. (1977).

No abstract.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Technical plan for the Great Lakes Environmental Research Laboratory. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 56 pp. (1977).

No abstract.

GRUMBLATT, J.L. Great Lakes water temperatures, 1966-75. NOAA Technical Memorandum ERL GLERL-11-2 (Full Microfiche Edition), Great Lakes Environmental Research Laboratory (PB-275-469/5GI) 127 pp. (1976).

A 10-year bank of water temperature data has been accumulated from a network of stations located at intervals along the United States shores of the Great Lakes and is presented in various tables. For each station, summaries of hourly, daily, and monthly mean data are included as well as tables of the frequency distribution of daily mean water temperatures on an annual basis.

GRUMBLATT, J.L. Great Lakes water temperatures, 1966-75. NOAA Technical Memorandum ERL GLERL-11-1, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB-275-468/7GI) 127 pp. (1976).

A 10-year bank of water temperature data has been accumulated from a network of stations located at intervals along the United States shores of the Great Lakes and is presented in various tables. For each station, summaries of hourly, daily, and monthly mean data are included as well as tables of the frequency distribution of daily water temperatures on an annual basis.

GRUMBLATT, J.L. Heat advection in Lake Ontario, 1972-73. GLERL Open File Report, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (1977).

No abstract.

HAGMAN, J.C. Environmental information requirements: GLERL user study. GLERL Open File Report, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (1977).

No abstract.

HUANG, J.C.K. A general circulation model for lakes. NOAA Technical Memorandum ERL GLERL-16, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB-281-834/2GI) 43 pp. (1977).

The model is based on time integration of the finite difference form of the primitive equations. Fresh water density is approximated as a quadratic function of temperature. Lake circulation is driven by imposed meteorological conditions. The flux form of a mass, momentum, and energy conservation numerical scheme is used for the finite difference equations of the model. Based on the simulated energetics, the major physA time-dependent, three-dimensional numerical dynamic model for a large lake, possessing the actual coastal configuration and bottom topography of the lake and with a flexible number of vertical layers, has been developed to simulate the organized water motion and temperature structure throughout the annual cycle of the lake and to understand the physical nature of the lake in response to atmospheric forcing. Typical processes and dominant dynamic mechanisms responsible for variations and fluctuations in lake properties are identified. Test runs have been carried out with the geometry and bathymetry of Lake Ontario on a 5-km grid with four vertical layers. Reported here are two cases with surface winds and heat similar to the mean state of July and November. Results show that the whole lake response is dominantly barotropic and gradually becomes baroclinic. The vertically integrated stream functions for southwest and northeast winds form a two-gyre circulation pattern. There is an elongated anticyclonic gyre in the north and a cyclonic one in the south in the former case, and reversed circulation in the latter case. The surface layer currents show strong coastal jets, about 10 cm/s, in the direction of the wind in the shallow regions and a weaker return flow in the middle of the lake. Lower layers contain return flows along the bathymetry of the deep lake to balance the pressure gradient due to the wind set-up. Some comparisons are made with International Field Year for the Great Lakes data and further improvements for the model are pointed out.

Hunt, G.W., and A. ROBERTSON. The effect of temperature on reproduction of Cyclops vernalis fischer (copepoda, cyclopoida). Crustaceana 32:169-177 (1977).

No abstract.

LESHKEVICH, G.A. Great Lakes ice cover, winter 1975-76. NOAA Technical Memorandum ERL GLERL-12, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB-271-255/2) 35 pp. (1977).

From ice-cover data received at the Great Lakes Environmental Research Laboratory during the past winter, 19 composite ice charts were produced to illustrate estimated ice distributions and concentrations on the Great Lakes at weekly intervals from mid-December 1975 through mid-April 1976. According to the definitions of mild, normal, and severe winters set forth by Rondy (1971), freezing degree-day accumulations indicate that the 1975-76 winter was normal for all lakes. Accumulations were at their seasonal maximum on 21 March in the northern portion of the Great Lakes and on 8 February in the southern portion. Skim ice was reported during lake November and early December at various sites around the Great Lakes. Freeze-over was reported in late November on some bays and protected areas of Lake Superior and the lower St. Marys River and near mid-December at other sites on the Great Lakes, including portions of Green Bay, Saginaw Bay, and Lake St. Clair. Responding to lower average weekly temperatures, ice growth continued on these and other protected shore areas during the week ending 21 December. During the next 2 weeks slightly warmer temperatures retarded ice growth, especially on the northern lakes. Ice growth increased substantially during the week ending 11 January, reflecting colder air temperatures. On the average, ice covers increased during lake January, reaching their maximum extents during early February on all lakes except Lake Superior, where it reached maximum near mid-March. Maximum ice extent was estimated to be approximately 40 percent on Lake Superior, 20 percent on Lake Michigan, 50 percent on Lake Huron, 95 percent on Lake Erie, and 20 percent on Lake Ontario. Warmer temperatures during the week ending 15 February caused substantial loss of ice cover on most of the Great Lakes and , except for short periods of relatively stable conditions, started the period of ice deterioration on the southern portion of the Great Lakes. On the northern portion of the Lakes ice covers continued to grow or remain relatively stable until the week ending 21 March, when warmer temperatures started a period of ice deterioration that continued to the end of the season. Last reports of significant ice on the northern lakes came near mid-April.

LIU, P.C. Applications of empirical fetch-limited spectral formulas to Great Lakes waves. Proceedings, 15th Coastal Engineering Conference, American Society of Civil Engineers, New York, 113-128 (1976).

Two episodes of Great Lakes waves for which both wind and wave data are simultaneously available are used to examine the applicability of the empirical fetch-limited spectral wave formulas developed by JONSWAP, Mitsuyasu, Liu, and Sverdrup-Munk-Bretschneider. Comparing the results hindcast from the formulas with those recorded shows that, for hindcasting significant wave heights, Liu's formula gives better results for less than fully developed waves, while formulas by JONSWAP, Mitsuyasu, and Sverdrup-Munk-Bretschneider give better results for fully developed waves. In hindcasting average wave periods and peak-energy frequencies, all the formulas result in a deviation of up to 2 s and 0.5 rad s-1, respectively. These results can be used as a reference in evaluating and interpreting wave predictions made by these formulas as applied to the Great Lakes.

**LIU, P.C. Temporal spectral growth and nonlinear characteristics of wind waves in Lake Ontario. Ph.D. dissertation, The University of Michigan, Ann Arbor, University Microfilms, Ann Arbor, MI, 154 pp. (1977).

No abstract.

NALEPA, T.F. Freshwater macroinvertebrates. Journal of Water Pollution Control Federation 49:1206-1218 (1977).

No abstract.

PICKETT, R.L. The observed winter circulation of Lake Ontario. Journal of Physical Oceanography 7:152-156 (1977).

Observations of Lake Ontario's monthly mean properties during the winter of 1972-73 suggest that currents and temperatures are nearly constant with depth and that the lake-wide mean circulation pattern consists of either one counterclockwise or two counterrotating gyres.

PICKETT, R.L., and D.B. RAO. One- and two-gyre circulations in homogeneous lakes. IFYGL Bulletin 19:45-49 (1977).

No abstract.

PINSAK, A.P. The role of Maumee Bay in level B planning strategies. Great Lakes Basin Commission, Communicator 7:5-6 (1977).

No abstract.

QUINN, F.H. Annual and seasonal flow variations through the Straits of Mackinac. Water Resources Research 13(1):137-144 (1977).

The present emphasis on Great Lakes water quality studies requires a knowledge of the average and variability of the net flow between Lakes Michigan and Huron. Average annual and average monthly flows through the Straits of Mackinac were computed for the 1950-1966 period by use of a water budget technique applied to Lakes Michigan and Huron. In addition, water budget computations were compared with a 100-day period of current meter observations taken in 1973. The computations and measurements agreed quite closely, within approximately 2%. A variation of greater than 500% was found between the maximum and minimum annual flows observed during the 17-year computation period. The gross residence or flushing time for Lake Michigan was determined by two methods. The first determination used the mean annual flow through the straits, resulting in a flushing time of 137 years. The second procedure using the results of the current study, which found a deep return flow into Lake Michigan through the straits during stratification, gave a flushing time of 69 years.

QUINN, F.H. Pressure effects on Great Lakes vertical control. Journal of the Surveying and Mapping Division, American Society of Civil Engineers, ASCE 102:31-37 (1976).

No abstract.

QUINN, F.H., and J.C. HAGMAN. Detroit and St. Clair River transient models. NOAA Technical Memorandum ERL GLERL-14, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB-272-132/2GI) 45 pp. (1977).

A series of hydraulic transient models have been developed for the St. Clair and Detroit Rivers to simulate hourly and daily flow rates. These flows are necessary for water quantity and quality studies of the Great Lakes. This memorandum describes the mathematical models, their calibration, sensitivity, and applications so that modelers and water resource planners can make use of them in their studies.

RAO, D.B. Calculating useful products from an oceanographic data base. Marine Sciences Directorate Manuscript Report Series No. 45. Marine Sciences Directorate, Ottawa, Ontario, Canada, 35 pp. (1977).

Some well-known methods are described for an analysis of available temperature and other data to obtain useful products; the importance of each of these products is pointed out. Also presented are an objective analysis technique that can resolve frontal characteristics and a procedure to predict the movement of oil slicks under the influence of random wind fields.

ROBERTSON, A. Availability of information for mapping plankton distributions in the Great Lakes. In Workshop on Environmental Mapping of the Great Lakes, D.R. Rosenberger and A. Robertson (eds.). International Joint Commission, Windsor, ON, 121-126 (1977).

No abstract.

Rosenberger, D.R., and A. ROBERTSON. Proceedings, Workshop on Environmental Mapping of the Great Lakes, Windsor, Ontario, Canada, November 8-10, 1976. International Joint Commission Great Lakes Research Advisory Board, 224 (1977).

No abstract.

SAYLOR, J.H. Physical limnology. In The Waters of Lake Huron and Lake Superior, Vol. II, Part B: Lake Huron, Georgian Bay, and the North Channel, Upper Lakes Reference Group (eds.). International Joint Commission, Windsor, Ontario, Canada, 295-350 (1977).

Physical limnology is the study of the physical processes occurring in freshwater lakes, including the physical interactions between the lakes and the overlying atmosphere. Knowledge of the physical processes is basic to the understanding of the chemical and biological processes occurring simultaneously. For example, currents affect the distribution of chemical substances and biological communities, and temperature affects chemical and biological processes. This section will discuss the following physical processes: water budget, thermal regime, circulation and water movement, interlake water exchange, and optical properties of the water. Each of these processes affects the pollutional status of the water bodies in some way. These effects will be discussed in general at the beginning of the appropriate section, then in detail as to how the processes specifically affects Lake Huron proper, Georgian Bay, and North Channel.

SAYLOR, J.H., and L.J. DANEK. Wind-driven circulation of Saginaw Bay. Proceedings, 15th coastal engineering conference, American Society of Civil Engineers, New York, 3262-3275 (1977).

A combination of Lagrangian measurements and fixed current meter moorings were used during the summer of 1974 and the winter of 1974-75 to determine the circulation patterns of Saginaw Bay. Because the bay is shallow, the water responds rapidly to wind changes. Distinct circulation patterns were determined for southwest and northeast winds. These directions parallel the major axis of the bay and were the prevailing wind directions during the study. A typical exchange rate between the inner and outer bay during moderate winds aligned with the bay axis is 3700 m3 s-1. If sustained, this flushing rate would completely exchange the water of the inner bay in about 26.5 days. However, winds perpendicular to the axis of the bay cause little water to be exchanged and the residence time of water in the bay is much longer. Comparison of measured currents with the results of an independently-developed numerical model for the bay indicates there is good agreement between the observations and the simulation of the circulation in the shallow inner bay. Agreement is poor in the deeper outer bay, where specification of proper boundary conditions at the open mouth of the bay is important for meaningful model simulations. Ice cover during winter shields the water surface from wind stress. Currents are sluggish and driven almost entirely from interactions with the lake-scale circulation of Lake Huron.

SAYLOR, J.H., and G.S. MILLER. Winter currents in Lake Huron. Technical Memorandum ERL GLERL-15, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB-275-847/2GI) 107 pp. (1976).

Twenty-one current meter moorings were deployed in Lake Huron during winter 1974-75. The moorings were set in November 1974 and retrieved approximately 6 months later. The stations were configured on a coarse grid to measure the lake-scale circulation during winter. Water temperature was also recorded in nearly all of the 65 current meters deployed. Results reveal a strong cyclonic flow pattern in the Lake Huron Basin persisting throughout the winter. The observed winter circulation was in essence very similar to what is now believed to be the summer circulation of empilimnion water, although the winter currents penetrated to deeper levels in the water column and were more intense. Winter cyclonic flow persisted in a nearly homogeneous water mass, while summer currents exhibited an almost geostrophic balance with observed water density distributions. This suggests that the current field driven by prevailing wind stresses across the lake's water surface may be largely responsible for establishing the horizontal gradients of water density observed in the lake during summer. Analyses of energetic wind stress impulses reveal the prevailing wind directions that drive the dominant circulations. The winter studies permit a description of the annual cycle of horizontal current speed variation with depth in Lake Huron, and in the other Great Lakes as well. The effects of ice cover are examined and the distribution and movement of the ice cover with respect to lake current and temperature fields are discussed.

SCAVIA, D., and S.C. CHAPRA. Comparison of an ecological model of Lake Ontario and phosphorus loading models. Journal Fisheries Research Board of Canada 34:286-290 (1977).

Predicted responses of Lake Ontario to phosphorus loads from two empirical relationships and an ecological model were compared. Predictions of annual average concentrations of total phosphorus and chlorophyll a by the ecological model were consistent with those predicted by the simpler models. We concluded that the use of a particular type of model is governed by the nature of the problems being addressed rather than an inherent superiority of either approach.

SCHWAB, D.J. An objective analysis scheme for lake currents. IFYGL Bulletin 19:50-52 (1977).

No abstract.

SCHWAB, D.J. Internal free oscillations in Lake Ontario. Limnology and Oceanography 22:700-708 (1977).

A numerical procedure is used to calculate some of the internal free modes of oscillation in a two-layer model of Lake Ontario, assuming a uniform equivalent depth. The modes fall into two categories, one set resembling Kelvin type waves and the other resembling Poincare-type waves. Observational evidence from Lake Ontario agrees qualitatively with the properties of these two types of modes.

SCHWAB, D.J., and D.B. RAO. Gravitational oscillations of Lake Huron, Saginaw Bay, Georgian Bay, and the North Channel. Journal of Geophysical Research 82:2105-2116 (1977).

Periods and structures of gravitational free oscillations in Lake Huron, Saginaw Bay, Georgian Gay, and the North Channel are determined from theoretical calculations. The calculations take into account the bathymetry and shape of the Huron system and also the effect of the earth's rotation. Time series analyses are performed on water level data from 13 stations around the lake. The power and coherence spectra exhibit peaks corresponding to diurnal and semidiurnal forcing and various modes of free oscillation of the lake. Both theory and observations show that Saginaw Bay, Georgian Bay, and the North Channel each have a fundamental frequency of oscillation lower than the frequency of Lake Huron's first longitudinal oscillation. There is reasonable agreement between theoretical and observed characteristics for several of the free modes of the Lake Huron system.

**TARAPCHAK, S.J., and E.F. Stoermer. Environmental status of the Lake Michigan region, Volume 4. Phytoplankton of the Lake Michigan region. Report No. ANL/ES-40 prepared for the U.S. Energy Research and Development Administration. GLERL and the University of Michigan under Contract No. W-31-109-Eng-38, Ann Arbor, MI, 211 pp. (1976).

For nearly 100 years, studies on the phytoplankton of Lake Michigan have provided a wealth of information on the flora, its quantitative composition, and the effects of cultural eutrophication on algal abundance and species composition. The flora, consisting of over 2000 known taxa, contains species characteristic of oligotrophic and eutrophic environments. Phytoplankton abundance and primary productivity vary seasonally and generally are higher and more variable inshore than offshore. Seasonal phytoplankton development is bimodal in the southern and nearshore water of the central basin but exhibits a unimodal pattern (a peak in summer) offshore in the central basin. These dissimilarities are attributed to differential effects of critical water temperatures, higher nutrient concentrations in the southern basin, and differences in critical mixing depths. The phytoplankton of the Lake historically has been dominated by diatoms. Recently there has been a significant increase in algal abundance inshore near Milwaukee and Chicago and a shift to a significant fraction of green and blue-green algae in the offshore community in the southern basin. This observation is one line of evidence suggesting that the Lake is undergoing serious cultural eutrophication due to increases in phosphorus loading rates. The trophic state of Lake Michigan, in general, is intermediate between Lake Superior and the western basin of Lake Erie. The present-day loading rate of phosphorus into the Lake is tolerable, according to Vollenweider's (1971) nutrient loading model; however, on a limited scale, southern Green Bay and certain inshore regions in the southern and central basin are receiving unacceptable loadings.

TARAPCHAK, S.J., and R.F. Wright. Three oligotrophic lakes in northern Minnesota. In North American project--A study of U.S. water bodies, L. Seyb and K. Randolph (eds.). U.S. Environmental Protection Agency, Corvallis, OR, 64-90 (1977).

No abstract.

Thomann, R.V., and D. SCAVIA. Some comments on a water quality model for deep reservoirs. Journal of the Water Pollutution Control Federation 49:507-509 (1977).

No abstract.

Ordering GLERL Publications:

To order a copy of GLERL publications not available for downloading at this site, please contact:

Nicole Rice
Publications Office
NOAA Great Lakes Environmental Research Laboratory
4840 S. State Rd.
Ann Arbor, MI 48108-9719 USA
734-741-2055 (FAX)