Before swimming or fishing in lakes, rivers, or oceans, check local water advisories.
You can’t tell whether an algae bloom is toxic just by looking at it, so the CDC advises, “When in doubt, stay out.” Don’t go into water that smells bad, is discolored, has dead animals floating in it, or has a foamy scum or paintlike streaks on its surface.
“You can tell a lake that has the algal blooms, that has that film on the top,” Erika Holland, an assistant professor of biological sciences at California State University, Long Beach, told BuzzFeed News. “As an experienced hiker, you’re always told not to drink from stagnant water.”
If you do come into contact with contaminated water, the CDC recommends that you rinse yourself as quickly as possible with clean fresh water. Seek medical treatment as soon as possible if you show any symptoms, or call the Poison Control Center.
For animals, be sure to also keep pets or livestock away from water experiencing harmful algal blooms.
If your dog does swim in a bloom, use clean fresh water to immediately wash them down, and stop them from licking any cyanobacteria that may still be on their fur. Call a veterinarian if the dog exhibits any stumbling, convulsions, foaming at the mouth, vomiting, or other unexplained symptoms.
Why are blue-green algae spreading?
Several human-induced factors are contributing to a spread in water conditions that lead to harmful algal blooms around the world.
The first is land management. Agricultural runoff, such as fertilizer, and urban runoff, such as sewage, are depositing extra nutrients into bodies of water, stimulating eutrophication. The construction of dams has also slowed water movement in some areas, creating stagnant bodies that foster cyanobacteria.
But climate change is also leading to hotter temperatures and warmer bodies of water that stimulate the growth of cyanobacteria. Droughts also lead to water and nutrients condensing in depressed lake levels.
“If we continue to see extreme warmth, if we continue to see droughts,” Caron said, “we will probably see more of these toxins produced and the potential for more animals and humans to get in the way of those toxins.”
