Written by Lake Ontario Waterkeeper
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Lake Ontario’s name comes from the Iroquoian language and means “lake of shining waters.” The First Nations were the first to live in the watershed, arriving some 7,000 years ago. Today, Lake Ontario is home - and a source of drinking water - to 9-million people living in Ontario, Canada and New York State, USA.

Because of the size of the lake and its connection to the Atlantic Ocean, Lake Ontario is an ecological wonder. All of the water in the Great Lakes flows through this lake. Fish travel back and forth from the ocean to the freshwater lake. Different parts of the lake offer different habitats, ranging from dunes to wetlands to forest to rocky cliffs.

Overfishing in the 1800s and pollution and development in the 1900s took their toll on Lake Ontario’s fish. Before dams on the St. Lawrence River restricted passage, fish like the eel and the sturgeon used to migrate between the lake and the ocean in enormous numbers.

Because of human activities, at least 10 species of fish have gone extinct and at least 15 exotic species have been introduced in the last 200 years. While some damage is irreparable, much of the restoration work being done around Lake Ontario is intended to bring some of the lake’s natural biodiversity.

The Great Lakes offer some of the best beaches in the world. Sandbanks Provincial Park in Prince Edward County, for example, is home to the largest freshwater dune system on earth. These unique beach ecosystems are also important habit for plants, animals, and migrating birds.

In the 1980s, 43 communities on the Great Lakes were designated “Areas of Concern” because of severe environmental degradation. The Lake Ontario Areas are: Bay of Quinte, Eighteen Mile Creek, Hamilton Harbour, Metro Toronto, Oswego River, Port Hope Harbour, and the Rochester Embayment. Today, the greatest threats to Lake Ontario come from urban development, electricity generation, and sewage and stormwater pollution.

Lake Ontario Waterkeeper works to restore and protect the lake because it is vital to the survival of our communities. Nine-million people rely on the lake for drinking water. Roughly 1 in 4 Canadians lives in the watershed. Few bodies of water are as important to so many people, which is why we work to ensure it will be swimmable, drinkable, and fishable for everyone.

Glacial History

The Laurentide Glacier once covered all of Canada. About 14,000 years ago, it began melting. As it retreated, the glacier left behind Lake Iroquois, a larger version of present-day Lake Ontario. If you have ever driven across Davenport Road in Toronto, you may have noticed the high ridge that separates the north side of the road from the south. This is Lake Iroquois’ original shoreline.

When part of the Laurentide Glacier in the St. Lawrence River valley melted away, water from Lake Iroquois rushed out to the Atlantic Ocean. A smaller lake, Lake Admiralty, was left behind. The old Lake Admiralty shoreline is underwater now, a “scarp” or bluff that runs from the Scarborough Bluffs to offshore of Hanlans Island in Toronto. Eventually, the rock under the lake and the Thousand Islands east of Kingston settled, and the Lake Ontario we know today was formed.

Quick Facts

  • Lake Ontario provides drinking water to 9-million people.
  • More Canadians live in the Lake Ontario watershed than any other watershed in the country.
  • The lake never completely freezes because it is so deep. The surface of Lake Ontario has frozen over at least five times, the last time in 1934.
  • Lake Ontario has a “seiche”, a natural rhythmic motion as water sloshes back and forth every 11 minutes.
  • Glaciers formed the lake between 14,000 and 10,000 years ago.
  • The lake is one of the 5 Great Lakes, which 21% of the world’s surface freshwater.
  • Lake Ontario is the 14th largest lake in the world.
  • All Great Lakes water flows through Lake Ontario before it flows to the Atlantic Ocean.
  • Water takes about 6 years to flow through Lake Ontario to the St. Lawrence River
  • Lake Ontario is the most threatened Great Lake.
  • Niagara Falls pours into Lake Ontario.
  • Iroquois and Huron First Nations lived on the lake for thousands of years before Europeans arrived.
  • “Lake Ontario” means “lake of shining waters”.
  • Commercial fishing peaked in the late 1880s; 130 years later, government and NGOs are still working to restore the lake’s native fish populations.
  • Lake Ontario is partially in Canada, partially in the USA.
  • There used to be 150 species of fish in the Great Lakes.
  • The most common fish in Lake Ontario used to be the American Eel.
  • There are over 100 beaches on Lake Ontario.

For More Information

Courtesy of Lake Ontario Waterkeeper

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