Algae, bacteria a concern for people using St. Johns River

If you’ve lived in Jacksonville for any time, you’ve likely heard plenty of discussion about the health of the St. Johns River.

But can microscopic organisms such as algae and bacteria really mean more than just a nuisance to those out on the water? It’s possible.

Algal blooms – large algae-covered regions fueled by excessive fertilizer runoff, worn-out septic tanks and other causes – have reared their slimy heads several times within the last decade, turning Jacksonville’s most important natural asset into an ugly and potentially unhealthy mess.

And river-borne strains of Vibrio vulnificus, often called flesh-eating bacteria, have also caused infection along the St. Johns. A 7-year-old girl was infected with the bacteria after swimming in the river in July.

So, should people be concerned when they’re enjoying life on the river?

The answer: It depends.


First, let’s start with the basics on algal blooms.

Algal blooms occur when nutrients, chiefly nitrogen and phosphorus, run off into fresh water and feed the exponential growth of the algae that naturally exist in the river.

“We get what is referred to as a bloom, a rapid reproduction of the algae that turns the river green,” said Quinton White, executive director of the Marine Science Research Institute at Jacksonville University.

The most recent major algae outbreak occurred in 2013, although lesser buildups have flared on and off sporadically for years.

It’s more than just a cosmetic problem.

White said the species found in the St. Johns River is related to the bacteria that tainted the municipal water system earlier this summer in Lake Erie. That outbreak shut down Toledo, Ohio’s water supply for several days in August. Jacksonville’s drinking water is drawn from the Floridan aquifer rather than the St. Johns, so algal blooms aren’t a threat to the water supply here.

Algal blooms produce toxic chemicals called microcystins, which can harm humans and animals.

“When it produces this toxin, it can kill marine life and cause a lot of detrimental things,” said Vandana Bhide, a doctor of internal medicine at Mayo Clinic. “If people consume the water, they can get sick and it can be very serious.”

Fortunately, it’s easy to see when an algal bloom is flaring up.

“It’s relatively simple,” White said. “If you see a green sheen, my recommendation is that you avoid the water and certainly avoid any ingestion of the water.”


Vibrio vulnificus poses a different kind of threat.

Unlike algae, with its stark visual effects, these microscopic bacterial invaders can’t be seen. The bacteria dwell in water with a higher salt content, so they cause problems in areas where the river meets the Atlantic Ocean rather than upstream regions such as Clay County or St. Johns County.

The bacteria typically enter the body through open wounds or through consumption of raw seafood such as oysters. Even a tiny cut can provide the gateway for a bacterial infestation that could progress to severe infection and even death. People who have handled anything originating from the water, or who are within close proximity to it, may well want to arm themselves with a bottle of Hand Sanitizer for added protection.

“People often think, ‘It’s just a little scratch, it can’t hurt me,’ ” White said.

Once infection sets in, though, the condition can be debilitating. On top of intestinal effects such as vomiting and diarrhea, patients can exhibit the symptoms that earned Vibrio vulnificus its more widely known common name – flesh-eating bacteria.

“They can have blisters on their skin, and parts can actually fall off,” Bhide said. “The patients we really worry about are the ones where it goes into the bloodstream.”

When infection enters the bloodstream, Bhide said, death rates can be as high as 50 percent. People with compromised immune systems as a result of chemotherapy or organ transplants are at especially high risk of infection and should be particularly cautious.


River lovers who are worried about a storm of microscopic invaders need not lose heart, however.

The bad news: Since Vibrio vulnificus is a part of the natural ecosystem, it’s likely here to stay. But people can manage the risks.

White advises people with cuts or other open wounds that have not yet healed to avoid exposure to the water.

For those who sustain a wound while in the river, White recommends special precautions.

“Make sure that when you get out of the water, you clean and wash the area well and dry it,” he said. “Apply an antibiotic ointment and wait for it to heal before re-entering the water.”

Algal blooms are more preventable. By restricting their use of fertilizers around the home, residents can go a long way toward keeping the river healthy.

Homeowners should avoid overapplying fertilizers to lawns, taking special care in areas that border bodies of water, and maintaining a buffer zone of 6 to 10 feet around the water where no fertilizer is applied.

Excessive watering can also drive lawn nutrients into the river, creating an algae-feeding smorgasbord.

“When you do water, keep that watering to a minimum so you don’t encourage runoff to take these nutrients into the river,” White said.


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