the great lakes and the greatest lake characteristics and processes physical and biological...

The Great Lakes and the Greatest Lake

Characteristics and processes

Physical and biological challenges

Local and global relationships

The Great Lakes System

• 18% of world’s fresh water [6 quadrillion gal]• Spread over “lower 48” states = 9.5 ft. deep• All among world’s top 20 lakes in surface area• Cover 94,000 sq mi• Drainage area (watershed) spans 100 of latitude

and 180 of longitude (750 miles W-E)• Home to 10% of US population and 25% of

Canadians

http://www.on.ec.gc.ca/glimr/images/maps/glbasin.gif

Formation of the Lakes

• Geologically very young

• Regional bedrock varies in hardness

• Forces of mountain building, volcanoes, metamorphism active in Pre-Cambrian around Lake Superior [1-2 BYA]

• Most of area sedimentary, Paleozoic age

Permian Period, 285 MYA(shale, Limestone, coal);Carboniferous Period, 320 MYA)(sandstone, shale, coal)

Devonian Period, 410 MYA(limestone, shale, sandstone)

Silurian Period, 440 MYA(Dolostone, some limestone)

Ordovician Period, 500 MYA(limestone, Cincinnati Arch)

Ohio Bedrock

Pleistocene Events shaped Ohio’s topography

Extent of glacial advance

Lake Superior

• Largest surface area of any lake in world

• Deepest of Great Lakes [1332 ft]

• Volume = all other lakes + 3 more Eries

• Retention time 191 years

• Watershed mostly forested, water quality high except for airborne transport

Lake Michigan

• The only GL entirely in the United States

• Cul-de-sac; water retention 99 years

• Same level as Huron; they act as one lake

• N is forested, S heavily urbanized (1/5 of basin population)

• Green Bay: productive fishery but contaminated by paper mills

• Home of world’s largest freshwater sand dunes

Lake Huron

• Includes Georgian Bay

• 30,000 islands! Manitoulin Island largest freshwater island in world

• Retention time 22 years

• Saginaw Bay fishery very productive

• Many shipwrecks, clear water for viewing

Lake Ontario

• 4x Lake Erie’s volume

• Niagara Falls flows into it

• Retention time 6 years

• Hamilton & Toronto, Ontario; not as dense on US side

Lake Erie

• Shallowest, smallest volume

• Retention time 2.6 years

• Most agriculture and urban effects on water

• Most productive in fish for human food

• “Poster child” for environmental concerns in 60s & 70s

Shipping importance

• More ships through Lake Erie in 9-mo season than through Panama,Suez, Manchester, and Kiel Canals put together

• Main commodities shipped: iron ore, grain, coal [bulk products]

• Most fuel efficient, environmentally friendly mode for transporting goods

• Seasonal [March 23-Dec 24, 2001]

• Declining in recent years

Regional environmental issues

• Non-native species– Ecosystem balance issues

• Water contamination– Bioaccumulation in food chain

– GLWQA, Areas of Concern

– Eutrophication

• Habitat loss and species change– Urban sprawl

– Fisheries changes

Fishery importance

• More fish from Lake Erie than all others together

• Economic changes from commercial to sport (stocked) fish in US waters

• Threatened by non-native species and environmental changes in

watershed

State of Lake Erie 2001

• Condition “mixed” to “mixed-deteriorating”– Contaminants– Nutrients– Non-native species– Habitat loss/alteration– Fisheries decline (walleye & perch)

Contaminants

• Toxic substances (PCBs, chlordane, DDT, dioxins, PAHs, pesticides, endocrine disruptors)

• Heavy metals (Pb, Hg)

• Nutrients (phosphates, nitrates)– Dead zone reappearing in recent years

– NO3 concentration increasing

Non-native species

Habitat

• Degraded wetlands, forests, beaches, dunes

• Land use issues in tributaries

• Open lake anoxic areas

Other organisms...

• Native unionid mussels– Abundance reflects ecosystem health– Absent from former habitats– ZM pressures, factory farms, herbicides

• Lake trout

• Scud• DELT (Deformities, eroded fins, lesions, tumors)

June 1997

July 1999

Lake Erie water levels at

Put-in-Bay, Ohio

Rich regional history & culture

• War of 1812: 2nd war for independence

• Civil War: John Brown, Johnson’s Island

• First Nations tribes (Iroquois, Walpole Island)

• Innovations in shipping: steamers, whalebacks, bulk carriers

• Burning river, dead lake success stories