Microscopic Summer Water Dangers
- Jackie Lochridge
- Sep 28
- 2 min read
What Are Harmful Algal Blooms (HAB)?
Harmful algal blooms occur when warm conditions and high nutrient content meet, creating ideal conditions for existing algae to explode in number and volume. Cyanobacteria blooms, also called "blue-green algae", occur in similar conditions, and are commonly considered harmful algal blooms. HAB can arise in a variety of aquatic environments including fresh and saltwater. There are a large number of organisms which can create HAB. Summer is a popular time to hit the water, but a run-in with a harmful algal bloom can ruin the fun. Exposure to HAB toxins by swallowing water is very dangerous for pets — if your pet becomes sick after being in or around water, seek veterinary care immediately. Eating fish or shellfish from waters with HAB and consuming contaminated blue-green algae supplements can also cause illness. Symptoms vary based on what organism is present in the bloom, but can include headache, nausea, diarrhea, and numbness.
How are HAB Identified?
Some algal blooms, like red tide, can be forecasted similar to a hurricane, allowing officials to direct testing efforts to high-risk areas. Cyanobacteria are monitored by various state and local agencies, and independent organizations offer plans and standards to create monitoring and hazard communication programs. Before you head to the ocean, lake, or river, be sure to check the status of the water.
What Can You Do?
While prediction (based on previous blooms) and testing for HAB are available, test results are not instantaneous. In the case of cyanobacteria, not all blooms produce toxins, so it's impossible to tell if the water is safe until testing has been conducted. If a body of water has a film, looks scummy, or smells bad, stay out. Report the potential HAB to your state's responsible department (this can be an environmental protection or wildlife agency) and/or to the Center for Disease Control's One Health Harmful Algal Bloom System (OHHABS).
Staying out of the water (e.g. in a boat) is safe, but direct contact with affected water carries higher risk for toxin exposure. If you, your pet, or someone you know has direct contact with suspicious water, wash well with warm soapy water. Be cognizant of fertilizing in the late summer, as runoff from lawns can increase nitrogen and phosphorous levels in bodies of water receiving rainwater, leading to algal blooms. Enjoy the water safely this and every summer by avoiding harmful algal blooms.
References
NOAA. What Is a Harmful Algal Bloom? Noaa.gov. Published April 27, 2016. https://www.noaa.gov/what-is-harmful-algal-bloom
CDC. Harmful Algal Blooms and Your Health. Harmful Algal Bloom (HAB)-Associated Illness. Published January 9, 2024. https://www.cdc.gov/harmful-algal-blooms/about/index.html
US EPA. What Are the Effects of HABs. www.epa.gov. Published August 16, 2018. https://www.epa.gov/habs/what-are-effects-habs
ITRC. Monitoring – HCB-1. Itrcweb.org. Published 2016. https://hcb-1.itrcweb.org/monitoring/
Lilly Center for Lakes and Streams. Blue-Green Algae Expert Guide. Lilly Center for Lakes & Streams. Published June 28, 2024. https://lakes.grace.edu/research/blue-green-algae/
Assessed and Endorsed by the MedReport Medical Review Board
