Don’t Feed the Algae

Green algae outbreaks are increasing in duration and frequency threatening our waterways and our health. In the spring and summer 2019, the St. Johns River experienced more than 90 days of outbreaks impacting more than 50% of our River.  Hotter temperatures, warming waters and runoff from frequent rainstorms during the summer could result in even more green muck coating our River. Unfortunately, there have already been several algae bloom sightings and reports in our River.

Nutrients? Aren’t those good for the River?

Algae blooms are visible symptoms of sickness and too much nutrient pollution in our waterways. Nutrients like nitrogen and phosphorus are naturally occurring in our environment.  However, in excess, they can undermine the ecological integrity of our waterways by depleting oxygen from the water, which negatively impacts plankton and causes fish die-offs, and hurting submerged grasses by blocking adequate sunlight. The River’s entire food web becomes severely harmed.

Join us as we take a deep dive into our River issues and summertime algae blooms. How are we connected to river pollution like algae blooms and what can we do to help? Watch all of our conversations and learn more. 

Health Impacts

Toxins produced by algae blooms can cause rashes, stomach cramps, nausea, diarrhea, and respiratory irritation. High exposure to toxins can affect the liver and nervous system. If skin contact occurs, wash off immediately and thoroughly with clean water and soap. Long-term exposure can potentially result in nerve or liver damage.

If citizens spot what looks like bright green paint-like, scum on the surface of the water, they should steer clear. Do not recreate, boat, swim, or fish near an algae bloom. 

Not all algae blooms are toxic, but active blooms should be avoided. 

So, 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.


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  REPORT@SJRK.ORG with photos, time, date and location.
  • To report fish that are either dead or sick, contact the Fish Kill Hotline 1-800-636-0511.


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:

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.

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.