Complete Guide to Red Tide in Florida

Last week I told you all about the stunning Beer Can Island my good friend Mackenzie and I stumbled upon a few weekends ago. What you didn’t know is that Beer Can Island, Siesta Key Beach and nearly every other Gulf Beach in the area was in the middle of Red Tide.

Red Tide in Florida In order to describe Red Tide I’ll need to use a certain amount of “science talk” and vocabulary. Don’t freak out, I’ll also be explaining it in layman’s terms.

What is Red Tide?

Red Tide is a common name for harmful algal bloom or HAB. Algae, that often green and usually slimy feeling substance that floats at the top of the water, plays a big role in the ecosystem of the ocean. The type of bloom that causes Red Tide happens when a species of dinoflagellate, or phytoplankton, known as Karenia brevis, blooms in excess. As the name implies, the bloom of this algae in high densities often turns the water a murky brown or reddish color.

Red TideVIA

Not all algal blooms are harmful, but a small percentage of algae produce powerful toxins that can kill fish, shellfish, mammals, and birds, and may even cause illness in people. Harmful algal bloom’s can also kill off large amounts of non-toxic algae. Without the algae the water becomes depleted of oxygen, thus causing a fish kill.

What is a Fish Kill?

A fish kill is one of the many effects Red Tide can have on an area. A fish kill is when a localized population of fish die-off. There are many many causes of a fish-kill but the most common is oxygen depletion.

The ocean is one of the most complex and (in my opinion) interesting ecosystems in the world. Just like a jungle or a desert there is a certain order to how the ecosystem functions. The sun, rain, animals and plants all (unknowingly) work together to make the ecosystem function in a natural way. The ocean works the same way, so when something causes the ecosystem to hit a snag, all of the plants and animals feel the that snag in varying degrees.

Fish KillVIA

Believe it or not, algae plays a huge role in keeping the ocean’s ecosystem stable. Algae use nutrients and produce oxygen through photosynthesis. Fish need oxygen to survive and most of the oxygen fish receive is from algae and this photosynthesis process. A disruption in this means the algae switches from the photosynthesis process to respiration, thus consuming the oxygen needed by the fish to survive.

So what causes the photosynthesis process to be interrupted? Well a lot of things, but most commonly a lack of sunshine. Sunshine is the one ingredient absolutely imperative to the photosynthesis process. Long periods of cloud cover and rain put a hold on the this process and cause an oxygen depletion in the water.

Fish Kill VIA

Fish can suffocate from lack of oxygen, but  most often the fish become stressed from a low oxygen level and become prone to viral or bacterial infections and die.

So do you spot a fish kill? Easy, the beach will be covered with dead fish that have washed up on the shore. More so than that, a strong and fowl smell of rotten fish will hit you well before you get even close to the beach.

What does Red Tide mean for travelers?

Red Tide not only makes the beach ugly and smelly, but it also makes it very unsafe. Getting in the water or eating seafood from the water during Red Tide can be extremely dangerous for people and animals.

Symptoms of people affected by Red Tide include abdominal pain, nausea, vomiting, diarrhea, reversal of hot/cold sensations, progressive sensations of tingling, pricking, or burning, muscle pain, headache, and vertigo. Swimming in Red Tide can lead to skin and eye irritation and rashes.

Red Tide WarningVIA

We didn’t let Red Tide ruin our day on Beer Can Island but we definitely kept away from dipping our toes in the water. We stopped at Siesta Key Beach after Beer Can Island and found that not only was the shore filled with dead fish, but the normal turquoise blue water was a dingy brown color. We again stayed out of the water. A few days later, I took my dogs to the Dog Beach at Venice Beach. The beach, which is normally very busy around sundown was almost vacant. After seeing all the dead fish on the beach, I put two and two together and realized the beach was probably empty because of the Red Tide.

What you should know

  • excessive blooming of the phytoplankton is Karenia brevis is what causes Red Tide
  • the blooming is natural and typically occurs in the late summer or early fall.
  • Red Tide can, and often does, cause a fish kill, which results in thousands of fish suffocating from lack of oxygen and washing up on the beaches or shores
  • Red Tide, as the name implies, turns the beautiful blue water to a murky brown or reddish color
  • people and pets should avoid getting in the water and eating seafood from the water during times of Red Tide
  • For a detailed and updated statewide status of Red Tide visit The Florida Fish and Wildlife Conservation Commission website.

Red Tide is naturally occurring in Florida, but there still is a lot to know and be aware about in regards to it. This read has gives you everything you need to know about Red Tide in Florida!

Have you ever heard of or experienced Red Tide?


  • Yuck! I had no idea that Red Tide was something that occurred quite often! It really is amazing how intricate all of the different ecosystems are all over the world and how if one thing is thrown off, it can really shake everything up.

    • I completely agree Ashley! Before I moved to Florida I had no idea about Red Tide. The thing is it usually happens in the late summer and early fall, and lets be real, florida is still miserably hot then so no tourists are visiting and even locals aren’t spending tons of time outside. So unless you live here (they talk about it on the news and there’s “red tide alerts” and such) you probably wouldn’t know about it.

    • ugh I know! the good part is unless you visit during the end of summer or beginning of fall you won’t ever have to deal with it. yay!

  • I studied a very small amount of marine ecology at university so I have a tiny understanding of this but enough to know that it’s definitely not something you want to swim in! I also didn’t know it happened so often that it regularly ruins your plans. That’s a bummer. It makes for a cool aerial shot but yeah… no.

    • lol. “yeah…no.” that pretty much sums it all up! I know some people who think the red tide stuff is overhyped, but I’m not getting anywhere near the water when it’s going on!

    • Marine biology is so interesting to me! How cool you got to take classes about it! I actually wanted to be a marine biologist when i was a little girl. I wanted to save dolphins and whales and stuff like that.

  • Megan Miller

    THE smelliest!!!