Don’t Feed the Algae

Toxic blue-green algae outbreaks, or harmful algae blooms (HABs), are increasing in duration and frequency threatening our waterways and our own health.  Nutrient pollution, warming waters and runoff from frequent rainstorms during the summer could result in even more green muck coating our River.

Aren’t nutrients good for the River?

Nutrients and blue-green algae, or cyanobacteria, are naturally occurring in our environment.  However, too much nitrogen and phosphorous (see sources of nutrient pollution below) can cause excessive algae growth that severely impacts the ecological balance and health of our waterways. Algae blooms can prevent sunlight from reaching underwater plants, clog fish gills, and deplete oxygen from the water, harming aquatic life and potentially causing fish kills.

Learn more about algae blooms what you can do to help. 

Health Impacts

If you encounter a green scum coating the surface of the water or green flecks or clumps suspended in the water column, it may be an algae bloom.  Avoid boating, swimming, or fishing in this area.

Toxins produced by some algae blooms can cause rashes, stomach cramps, nausea, diarrhea, and respiratory irritation.  

High exposure to some algal toxins can potentially even harm the liver and nervous system. 

If you or your pet come in contact with a bloom, wash off immediately and thoroughly with clean water and soap. 

Contact a veterinarian if your pet suddenly becomes lethargic or shows signs of poisoning including vomiting, diarrhea, or seizures.


Where are all the excess nutrients coming from?

Some of the major sources of nutrient pollution (phosphorous and nitrogen) in the St. Johns River:

  • The application of sewage sludge (also known as biosolids) on agricultural lands surrounding our River’s Headwaters at Blue Cypress Lake
  • Fertilizer run-off from agricultural, urban, and residential lands
  • Septic tanks
  • Industrial wastewater discharge and sewage spills
  • Aquatic spraying
  • Reclaimed water
  • Atmospheric deposition

Where can I find the locations of recent algae blooms?

Before you get out on the water, visit the Florida Department of Environmental Protection’s website to see an interactive map of algae bloom samples and results in our waterways.

Take Action

Report Algae Blooms

There is no standard duration for a bloom and no way to determine visually whether a bloom is toxic.

  • Report blooms to the Florida Department of Environmental Protection at or call toll free at 1-855-305-3903.
  • Email with photos, time, date and location.
  • To report fish that are either dead or sick, contact the Fish Kill Hotline 1-800-636-0511.


Contact Your State Legislators

Let your state legislators know that we need more protective regulations in place to prevent sewage sludge and other nutrient sources from causing algae blooms and polluting our waterways. Tell them to get the job done next session by stopping pollution at its source. Find your legislators:

Contact Your Local Leaders

Tell your Mayor, City Council, or County Commissioners that we need to enact stronger fertilizer ordinances and enforce the ones we have! Let’s lead by example in our parks and homes to stop pollutants from reaching our creeks, lakes, canals, and waterways.

Be River Friendly

Eliminate or reduce your use of fertilizer and reduce your impact on the health of our river. Learn how to live a more River Friendly lifestyle.

Educate yourself and others by attending one of St. Johns Riverkeeper’s educational programs and events.

Spread the word! Share what you know with your friends and family and encourage them to be more River Friendly. Follow us on Facebook.