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Understanding Algal Blooms: A Guide for Outdoor Enthusiasts

June 17, 2026 · The Clime Team
Understanding Algal Blooms: A Guide for Outdoor Enthusiasts

As outdoor enthusiasts, it's essential to be aware of harmful algal blooms (HABs) that can impact water quality and safety. These blooms occur when algae grow rapidly, producing toxins harmful to humans, animals, and the environment. Recognizing and avoiding HABs can help ensure your outdoor activities remain safe and enjoyable.

What Are Harmful Algal Blooms?

Harmful algal blooms are overgrowths of algae in water bodies, such as lakes, rivers, and oceans. Some algae produce toxins that can harm people, animals, and the environment. These blooms can change the water's color to green, blue, brown, or red and may appear as scum, foam, or mats on the surface. (cdc.gov)

How to Recognize a Harmful Algal Bloom

Before engaging in water activities, look for signs of a harmful algal bloom:

  • Discolored Water: Water may appear green, blue, brown, or red.

  • Surface Scum or Foam: The water's surface may have scum, foam, or mats of algae.

  • Unpleasant Odors: Decaying algae can release gases that smell like rotten eggs or rotting plants.

  • Dead Fish or Animals: The presence of dead fish or other animals along the shoreline can indicate a harmful algal bloom. (cdc.gov)

Health Risks Associated with Harmful Algal Blooms

Exposure to water contaminated by harmful algal blooms can lead to various health issues, including:

  • Skin Irritation: Contact with contaminated water can cause rashes or other skin problems.

  • Respiratory Issues: Inhaling airborne toxins from the water can lead to coughing, sneezing, or difficulty breathing.

  • Gastrointestinal Illnesses: Swallowing contaminated water can result in nausea, vomiting, or diarrhea.

  • Neurological Symptoms: In severe cases, exposure can lead to headaches, dizziness, or even more serious health effects. (cdc.gov)

Preventing Illnesses Caused by Harmful Algal Blooms

To protect yourself and others: (cdc.gov)

  • Check for Advisories: Before visiting bodies of water, look for swimming, fishing, or shellfish advisories from local authorities.

  • Avoid Contact: Stay out of water that appears discolored, has scum, foam, or emits an unpleasant odor.

  • Keep Pets and Livestock Away: Ensure that animals do not drink or come into contact with contaminated water.

  • Rinse Off After Exposure: If you come into contact with water that may be contaminated, rinse off immediately with clean water.

What You Can Do to Help

You can contribute to reducing harmful algal blooms by:

  • Reducing Nutrient Pollution: Limit the use of fertilizers, pesticides, and herbicides on your lawn or garden to prevent nutrient runoff into water bodies.

  • Planting Native Vegetation: Native plants require fewer chemical treatments and help maintain a balanced ecosystem.

  • Proper Waste Disposal: Dispose of pet waste properly to prevent nutrient pollution in water bodies. (epa.gov)

Staying Informed

Regularly check local advisories and stay informed about water quality in areas you plan to visit. By being proactive and aware, you can enjoy outdoor activities safely while protecting yourself and the environment.

Highlights:

  • How to Spot and Avoid Algal Blooms - Consumer Reports, Published on Monday, August 12
  • I Didn't Know That!: Harmful Algal Blooms (U.S. National Park Service), Published on Sunday, December 22

Frequently Asked Questions