St. Lawrence Seaway
Ecology

To create a navigable channel through the Long Sault rapids and to allow hydroelectric stations to be established immediately upriver from Cornwall, Ontario, and Massena, New York, Lake St. Lawrence was created behind a dam. This required the condemnation and acquisition by the government of all the properties of six villages and three hamlets in Ontario; these are now collectively known as The Lost Villages. The area was flooded beginning on July 1, 1958, creating the lake. There was also inundation on the New York side of the border, and the village of Louisville Landing was submerged.

A notable adverse environmental effect of the operation of the seaway has been the introduction of numerous invasive species of aquatic animals into the Great Lakes Basin. The zebra mussel has been most damaging in the Great Lakes and through its invasion of related rivers, waterways, and city water facilities. Invasive species and artificial water level controls imposed by the seaway have had a negative impact on recreational fishing.

The seaway, along with the St. Lawrence River it passes through, also provides opportunities for outdoor recreation, such as boating, camping, fishing, and scuba diving. Of note, the Old Power House near Lock 23 (near Morrisburg, Ontario) became an attractive site for scuba divers. The submerged stone building has become covered with barnacles and is home to an abundance of underwater life. The seaway passes through the St. Lawrence River, which provides a number of diveable shipwrecks within recreational scuba limits (shallower than 130 ft (40 m)). The region also offers technical diving, with some wrecks lying at 240 ft (73 m). The water temperature can be as warm as 75 °F (24 °C) during the mid- to late-summer months. The first 10 ft (3 m) of Lake Ontario is warmed and enters the St. Lawrence River, as the fast-moving water body has no thermocline circulation.

On July 12, 2010, Richelieu (owned by Canada Steamship Lines) ran aground after losing power near the Côte-Sainte-Catherine lock. The grounding punctured a fuel tank, spilling an estimated 200 tonnes (440 thousand pounds) of diesel fuel, covering approximately 500 square metres (5,400 sq ft). The seaway and lock were shut down to help contain the spill.
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