Environmental Observations

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· Water
· Pollution
· Plants
· Animals
· Weather and Climate
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Water
Water levels on the Great Lakes can vary by as much as 3 feet (1 meter) over periods of several years. During storms, the lake levels can rise or fall as much as 7 feet (2 meters), especially on the shallowest of the Great Lakes- Lake Erie. Long-term variations in the water levels are due to changes in precipitation. When lake levels are high, shoreline erosion is a major problem. When lake levels are low shipping, recreational opportunities, power generation, and wildlife habitats are threatened. Among the Great Lakes, Lake Ontario and Lake Superior are the only lakes whose water levels are regulated for hydroelectric power generation. A dam at Kingston, Ontario, controls Lake Ontario’s levels while gates at Sault Sainte Marie on the Saint Marys River regulate Lake Superior.

Lake Superior Water Levels 1860-2000
Lake Michigan-Huron Water Levels 1900-2000
Lake Erie Water Levels 1900-2000
Lake Ontario Water Levels 1900-2000
Lake St. Clair Water Levels 1910-2000

NOAA Great Lakes Water Levels Page
USGS Real-Time Water Data for Michigan
Historic Water Level Data From Great Lakes
GLIN Historical Great Lakes-St. Lawrence Water Levels
TEACH Water Levels on the Great Lakes
TEACH How Lake Levels and Flows are Measured

For additional information on the Great Lakes watersheds, please visit the Watershed page.

For health concerns related to the Great Lakes water, please visit the Health Issues page.

Pollution
Agricultural runoff, industrial discharges, and municipal sewage are the many sources of pollution in the Great Lakes. Increases in phosphorus levels generated considerable public concern in the lower lakes during the 1960s. The increased levels were caused by municipal wastewater discharges and agricultural use of fertilizers. Phosphorus gives rise to the growth of algae, which when decays causes oxygen depletion in the water; this in turn threatens many species of fish. In the meantime, other pollution-tolerant organisms thrive.

Lately, pesticides like dichlorodiphenyltrichloroethane (DDT) and industrial pollutants like polychlorinated biphenyls (PCBs) have been a big concern. Many residents around the Great Lakes are warned to limit the amount of fish intake from the lakes because these toxic contaminants accumulate within marine life. There have been several agreements between Canada and the United States that have addressed water-quality issues in the Great Lakes; among them are the Boundary Waters Treaty (1909) and the Great Lakes Water Quality Agreements (1927 and 1978). These agreements are implemented and regulated by the International Joint Commission on the Great Lakes, established under the Boundary Waters Treaty. The commission also has limited authority to adjust water boundary obstructions or diversions that might affect the natural water level or flow of the lakes.

For health concerns related to pollution in the Great Lakes, please visit the Health Issues page.

Plants

There are many native as well as non-native plants in the Great Lakes region. The most common non-native plant is the purple loosestrife. Because of its beauty, it was once used in landscaping. However, the purple loosestrife soon took over riverbanks and wetlands and invaded native plant areas.

Some common native plant species of the Great Lakes Basin are the white pine, the blue violet, and the white oak. The white pine is considered to be the largest conifer in the northeastern United States. It has soft blue-green to silver-green needles arranged in bundles of five. In the lower penninsula of Michigan and in Wisconsin, the eastern white pine forests were clear-cut for lumber from the mid to late nineteenth century. Current reforestation efforts are beginning the slow regrowth of the white pine. The blue violet inhabits the entire Great Lakes basin. Its colors can range from blue to lilac, green, yellow, and white. The white oak can grow to 100 feet tall and has grayish-white bark and brown-green acorns. When autumn arrives, the leaves on the white oak turn a variety of colors, such as red, gold, or purple.

Some rare species are Houghton's goldenrod and the American chestnut. The Houghton's goldenrod only grows along the shoreline of the Great Lakes; it can be found nowhere else in the world. The have a high concentration near the northern shores of Lake Huron and Lake Michigan. This goldenrod has been listed as a threatened species due to increased human activity along the shorelines. The American chestnut tree used to be abundant in the eastern Great Lakes region. However, a chestnut blight in the early twentieth century has practically rendered this species obsolete.

Brief Floral History of the Great Lakes Basin - TEACH Great Lakes
State and Provincial Flora

Animals

Exotic/Invasive Species

A major environmental problem facing the Great Lakes is the introduction of invasive species into the environment. Invasive species are non-native species that have been, in most cases, artificially introduced to the Great Lakes. Many of these organisms bring ecological instability and dominate native species they compete with, sometimes causing their extinction. Below is a list of common and notable invasive species in the Great Lakes, as well as information about them.

Sea Lamprey

The Sea Lamprey is one of the first exotic species to enter the Great Lakes, and one of the most destructive. They are primitive fish that have no bones or scales. Sea Lampreys are parasites that feed on other fish. They attach their mouths to fish and feed on its blood and body fluids with the help of a rasping tongue. A single sea lamprey destroys 40 lbs of fish in its lifetime. In the 1940’s and 1950’s sea lampreys devastated the fishing industry of the Great Lakes, reducing the amount of fish caught in Lake Huron and Lake Superior from 15 million lbs to 300,000 lbs annually. Methods for population control have been developed since then which include lampricide, spawning path barriers and male sterilization. Most areas have seen a 90% population reduction as a result, but population control still needs to be implemented.

Zebra Mussel

This invasive species was first found in the Great Lakes in 1988. They are the only fresh water mollusk that can attach firmly to any solid object. The mussels are very prolific in some areas, especially Lake Erie, where a square meter may contain 30,000 to 70,000. Colonies grow rapidly in areas where there is particulate food, ample oxygen and a current typically less than 6 feet per second. Zebra mussels act as water filters, with the ability to filter one liter of water per day. Nearly all particulate matter, which includes phytoplankton and zooplankton, is removed. As a result, water clarity has increased in the Lakes. As a result, more rooted aquatic plants have appeared in shallow bays due to increased sunlight penetration. Zebra mussels are causing many native mussels to become endangered and extinct. They also pose threat to industry, as they clog water intake systems of boats and industrial facilities. Research has been conducted that links zebra mussels with outbreaks of toxic blue-algae, due to the selective filtering by the mussel.

Minnesota Sea Grant

Spiny Waterflea

The spiny waterflea is a crustacean and carnivorous zooplankton that has most likely become a permanent member of the Great Lakes ecosystem. The waterflea competes directly with juvenile fish over other zooplankton, and as a result has been detrimental to fisheries.