Climate Change’s Potential Effects on Lake Ontario, USA and Canada43.6N 78.1W
Climate change threatens Lake Ontario (center) in a variety of ways, including a change in the distribution of fish species, the spread of invasive species, an increase in Summer stratification, loss of Winter ice and the release of nutrients and contaminants.
Stratification of lakes occurs when a warm surface layer of water develops over cooler, deeper water. A warming climate increases the duration of summer stratification in the deep lakes. This, in turn, makes frequent and larger “dead zones”—areas of water depleted of oxygen and unable to support life—more likely to occur, a risk especially for Lakes Erie and Ontario. Persistent dead zones can result in toxic algal blooms; foul-smelling, musty-tasting drinking water; damage to fisheries; and massive fish kills—known as “summerkill”.
Declines in the duration of winter ice on lakes are expected to continue. The loss of winter ice may be a mixed blessing for fish, reducing winterkill from oxygen deficits in shallow lakes but also jeopardizing reproduction of whitefish in the Great Lakes bays, where ice cover protects the eggs from winter storm disturbance.
Lower oxygen and warmer temperatures promote greater microbial decomposition and subsequent release of nutrients and contaminants from bottom sediments. Phosphorus release would be enhanced, and mercury release and uptake by biota would also likely increase—exposing humans to higher mercury levels via fish consumption (click here for more information).