In lakes, rivers and other fresh water, harmful algal blooms are most often caused by cyanobacteria, also called blue-green algae. They can make toxins that sicken people and animals, with symptoms ranging from mild to serious depending on the amount and type of toxin.
Image from CDC's page on symptoms caused by freshwater harmful algal blooms.
Symptoms in people
| How you're exposed | Possible symptoms |
|---|---|
| Skin contact with the water, or breathing in tiny droplets from a bloom | Rash; eye or nose irritation; sore throat; cough |
| Swallowing water, fish, shellfish or dietary supplements containing the toxins | Stomach pain, vomiting, diarrhea, headache, muscle weakness, dizziness, liver damage |
If you think a bloom made you sick, contact a health care provider or Poison Control at 1-800-222-1222 for advice.
Harmful algae can make different toxins that contaminate water and food. Image from CDC's page on symptoms caused by freshwater harmful algal blooms.
Long-term effects
The long-term effects on people and animals are still unclear. One compound cyanobacteria make, BMAA (beta-N-methylamino-L-alanine), has been linked in some animal research to harm to the brain, raising concern that it might contribute to brain and nervous system diseases. More research is needed, but a 2017 review by the U.S. Environmental Protection Agency concluded that current data do not show BMAA causes brain disease in humans.
Deadly for animals
Call a veterinarian immediately if pets or livestock seem sick after being in or near water: animals can become very sick or die within hours of swallowing cyanobacterial toxins.
Dogs, livestock, wildlife and birds can swallow the toxins by swimming in or drinking bloom water, or by eating algae, fish or other animals that contain them. Watch for:
- vomiting;
- loss of energy;
- staggering;
- excessive drooling;
- difficulty breathing;
- tremors and seizures.
Fish and other water life
Blooms harm aquatic animals in several ways:
- the toxins can kill them directly;
- when bloom cyanobacteria die and decay, they can use up the oxygen in the water, suffocating fish;
- dense cyanobacteria can make it hard for animals with gills to breathe.
Sources
Based on "Symptoms Caused by Freshwater Harmful Algal Blooms," Centers for Disease Control and Prevention; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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