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The Great Lakes:
 An Environmental Atlas and Resource Book

Chapter One - Introduction: The Great Lakes

Chapter Two - Natural Processes in the Great Lakes

Chapter Three - People and the Great Lakes

Chapter Four - The Great Lakes Today - Concerns

Chapter Five - Joint Management of the Great Lakes

Chapter Six - New Directions for the Great Lakes Community

Conversion Table (Metric to Imperial Values)
References and Suggestions for Further Reading
Sources for Maps


Alga (pl. Algae)
Simple one-celled or many-celled micro-organisms capable of carrying on photosynthesis in aquatic ecosystems.
The absence of oxygen necessary for sustaining most life. In aquatic ecosystems, this refers to the absence of dissolved oxygen in water.
Area of Concern
An area recognized by the International Joint Commission where 1 or more of 14 beneficial uses are impaired or where objectives of the Great Lakes Water Quality Agreement or local environmental standards are not being achieved.
Atmospheric Deposition
Pollution from the atmosphere associated with dry deposition in the form of dust, wet deposition in the form of rain and snow, or as a result of vapor exchanges.
Biochemical Oxygen Demand
The amount of dissolved oxygen required for the bacterial decomposition of organic waste in water.
A cumulative increase in the concentration of a persistent substance in successively higher trophic levels of the food chain (i.e., from algae to zooplankton to fish to birds).
Total dry weight of all living organisms in a given area.
The use of organisms to test the acute toxicity of substances in effluent discharges as well as the chronic toxicity of low-level pollutants in the ambient aquatic environment.
Cancer-causing chemicals, substances or radiation.
Consumptive Use
Permanent removal of water from a water body. Consumptive use may be due to evaporation or incorporation of water into a manufactured product.
Dichloro-diphenyl-trichloroethane - a widely used, very persistent pesticide in the chlorinated hydrocarbon group, now banned from production and use in many countries.
Dissolved Oxygen
The amount of oxygen dissolved in water. See Anoxia and Biochemical Oxygen Demand.
Transfer of water from one watershed to another.
Drainage Basin
A waterbody and the land area drained by it.
The interacting complex of living organisms and their non-living environment.
Waste waters discharged from industrial or municipal sewage treatment plants.
The warm, upper layer of water that occurs in a lake during summer stratification.
The wearing away and transportation of soils, rocks and dissolved minerals from the land surface or along shorelines by rainfall, running water, or wave and current action.
The process of fertilization that causes high productivity and biomass in an aquatic ecosystem. Eutrophication can be a natural process or it can be a cultural process accelerated by an increase of nutrient loading to a lake by human activity.
Exotic Species
Species that are not native to the Great Lakes and have been intentionally introduced or have inadvertently infiltrated the system.
Food Web
The process by which organisms in higher trophic levels gain energy by consuming organisms at lower trophic levels.
Human Health
The state of complete physical, mental and social well-being and not merely the absence of disease or infirmity (World Health Organization).
Hydrologic Cycle
The natural cycle of water on earth, including precipitation as rain and snow, runoff from land, storage in lakes, streams, and oceans, and evaporation and transpiration (from plants) into the atmosphere.
The cold, dense, lower layer of water that occurs in a lake during summer stratification.
Materials suspended or dissolved in water and other liquids, usually from waste sites, which percolate through soils and rock layers.
Mass Balance
An approach to evaluating the source, transport and fate of contaminants entering a water system as well as their effects on water quality.
See Trophic Status
Agriculture that is based on a single type of crop.
Nonpoint Source
Source of pollution in which pollutants are discharged over a widespread area or from a number of small inputs rather than from distinct, identifiable sources.
A chemical that is an essential raw material for the growth and development of organisms.
See Trophic Status
Disease-causing agents such as bacteria, viruses and parasites.
PCBs - polychlorinated biphenyls
A class of persistent organic chemicals that bioaccumulate.
A process occurring in the cells of green plants and some micro-organisms in which solar energy is transformed into stored chemical energy.
Minute, microscopic aquatic plant life (see Alga).
Point Source Pollution
A source of pollution that is distinct and identifiable, such as an outfall pipe from an industrial plant.
The conversion of sunlight and nutrients into plant material through photosynthesis, and the subsequent conversion of this plant material into animal matter.
Resuspension (of sediment)
The remixing of sediment particles and pollutants back into the water by storms, currents, organisms and human activities such as dredging or shipping.
An oscillation in water level from one end of a lake to another due to rapid changes in winds and atmospheric pressure. Most dramatic after an intense but local weather disturbance passes over one end of a large lake.
Stratification (or Layering)
The tendency in deep lakes for distinct layers of water to form as a result of vertical change in temperature and therefore in the density of water. See also Epilimnion, Hypolimnion, Thermocline
A layer of water in deep lakes separating the cool hypolimnion (lower layer) from the warm epilimnion (surface layer).
Toxic Substance
As defined in the Great Lakes Water Quality Agreement, any substance that adversely affects the health or well-being of any living organism.
Trophic Status
A measure of the biological productivity in a body of water. Aquatic ecosystems are characterized as oligotrophic (low productivity), mesotrophic (medium productivity) or eutrophic (high productivity).
Wind Set-up
A local rise in water levels caused by winds pushing water to one side of a lake.
Minute aquatic animal life.

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Conversion Table

Metric to Imperial Values
1 metre = 3.28 feet
1 kilometre = 0.621 miles
1 kilogram = 2.2 pounds
1 square kilometre = 0.386 square miles
1 cubic kilometre = 0.24 cubic miles
1 litre = 0.264 U.S. gallons
1 cubic metre/second = 35.31 cubic feet/second
1 tonne = 1.1 short tons

References and Suggestions for Futher Reading

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Sources for Maps and Production Credits (Print)

Relief, Drainage and Urban Areas

Geology and Mineral Resources

Climate Maps

The Great Lakes Water System

Historical Map

Land Use, Fisheries and Erosion

Waterborne Commerce

Recreation and Sports

Employment and Industrial Structure

Transportation and Energy Maps

Distribution of Population

State of the Lakes

Ecoregions, Drainage Basins and Wetlands

Production of Print Version

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