Lying along the border between the United States and Canada, Lake Superior is the northernmost of the Great Lakes. Its location has historically kept its waters cold, which in turn kept them clear. But The Conversation reports a disturbing trend of algal blooms within the last 12 years.
What's happening?
Algal blooms occur when harmful algae start multiplying out of control in a body of water. Excess nutrients, warm temperatures, and sunlight all contribute to the phenomenon.
In a small body of water such as a pond, algae can be controlled through measures such as pond dye that block sunlight. But Lake Superior is much too large and complex for that kind of intervention.
In the past, there were no recorded algal blooms at Lake Superior. But in 2012, The Conversation reported that its southern shore experienced a bloom, and more have occurred every year since 2016. Worse, blooms started on the northern shore in 2019.
The factors contributing to these algal blooms are human-caused. Heat-trapping air pollution has warmed the planet and made Lake Superior the fastest-warming lake in the world, according to The Conversation — reducing the time it's covered in ice by two months in the last 150 years. In 2024, only 12% of its surface froze, about one-fifth of the ice cover in a typical winter.
Also, the area is now taking on more nutrient-rich runoff from agriculture and urban areas.
Why do algal blooms matter?
The "algae" in these blooms is actually a type of bacteria called cyanobacteria, The Conversation explained. Not only does the cyanobacteria cloud the water and block sunlight from other plants, but in the right conditions, it can also produce toxins that harm people and the environment.
At best, an algal bloom in a body of water that people drink from causes an unpleasant taste and smell; at worst, it interferes with water treatment processes, causes digestive issues and liver damage in humans, and can kill pets and livestock.
What's being done about algal blooms?
Step one in dealing with algal blooms is monitoring; if you notice unusually murky and greenish water, report it to a local environmental office. Avoid spending time in the water since it's unknown what conditions will cause the cyanobacteria to produce toxins.
In the long run, the only way to protect our water from this phenomenon is to address the causes. That means using less fertilizer and reducing the use of dirty energy that pollutes the air and heats up the planet. You can also spread the word to your friends and family.
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