Is St Johns River safe? Toxic algae status
Putnam County, Florida. Harmful algal bloom (blue-green algae) reports from the Florida Department of Environmental Protection (DEP).
Data checked 24 October 2026. Florida data is published as a yearly file; current sampling is shown on the DEP dashboard.
80
sampling visits since 2018
47
visits where a bloom was seen
0.91 µg/L
highest microcystin result
Year by year
Each box shows visits where a bloom was seen, out of all sampling visits that year.
Reports at St Johns River are most often logged in July, August and September.
Recent reports
| Date | Location | Result |
|---|---|---|
| 19 November 2025 | St. Johns River - Buzzard Island | No bloom seen · microcystin not detected |
| 6 November 2025 | St. Johns River - Buzzard Island | Bloom seen · microcystin not detected |
| 23 October 2025 | St. Johns River - Buzzard Island | Bloom seen · microcystin not detected |
| 15 October 2025 | St. Johns River - Buzzard Island | Bloom seen · microcystin not detected |
| 2 October 2025 | St. Johns River - Buzzard Island | No bloom seen · microcystin not detected |
| 25 September 2025 | St. Johns River - Buzzard Island | Bloom seen · microcystin not detected |
| 23 September 2025 | St. Johns River - Racy Point | Bloom seen · microcystin not detected |
| 16 September 2025 | St. Johns River - Buzzard Island | Bloom seen · microcystin not detected |
| 26 August 2025 | St. Johns River - South of HWY 17 Bridge | No bloom seen · microcystin not detected |
| 19 August 2025 | St. Johns River - Buzzard Island | Bloom seen · microcystin not detected |
| 13 August 2025 | St. Johns River - Buzzard Island | Bloom seen · microcystin not detected |
| 12 August 2025 | St. Johns River - Racy Point | Bloom seen · microcystin not detected |
What the results mean
Staff saw a bloom at the sampling site. A sample may then be tested for toxins.
Microcystin, a liver toxin made by blue-green algae, was found in the sample.
At or above the level where the US EPA recommends swimming advisories for microcystins.
Dogs and toxic algae
Dogs face the greatest risk because they swallow water and lick algae off their fur. If a bloom has been reported, keep dogs out of the water and away from scum on the shore. If your dog swims in water that might have algae, rinse it with clean water straight away and call a vet if it seems unwell.
Common questions
Is St Johns River safe to swim in?
The most recent entry in Florida's published data is from 19 November 2025: no bloom seen · microcystin not detected (St. Johns River - Buzzard Island). Blooms have been recorded at St Johns River in 6 different years, so treat green, scummy or discoloured water with caution. For current conditions, check the DEP Algal Bloom Dashboard and posted signs.
When does St Johns River get algae blooms?
In the state's records, reports are most often logged in July, August and September. Blooms are most likely in warm, calm weather, but they can appear at other times of year.
Source: Florida Department of Environmental Protection (DEP), official data. This page is independent and not affiliated with the State of Florida.