A red tide, or harmful algal bloom, is a higher-than-normal concentration of microscopic alga. In Florida and the Gulf of Mexico, the species that causes most red tides is Karenia brevis.
At high enough concentrations, Florida red tide can discolor water a red or brown hue. Other algal species can appear red, brown, green or even purple. At lower concentration, the water color appears normal during a bloom.
Red tides were documented in the southern Gulf of Mexico as far back as the 1700s and along Florida’s Gulf coast in the 1840s. Fish kills near Tampa Bay were even mentioned in the records of Spanish explorers.
The duration of a bloom can be as little as a few weeks or longer than a year. In nearshore Florida waters, it depends on sunlight, nutrients and salinity. The speed and direction of the wind a water currents are also factors.
K. brevis cannot tolerate low-salinity waters for very long, so blooms usually remain in salty coastal waters and do not penetrate upper reaches of estuaries. However, other harmful algae, including cyanobacteria (blue-green algae), typically bloom in freshwater lakes and rivers.
Many red tides produce toxic chemicals that can affect both marine organism and humans. The Florida red tide organism, K. brevis, produces brevotoxins that can affect the central nervous system of fish and other vertebrates, causing these animals to die. Wave action can break open K. brevis cells and release these toxins into the air, leading to respiratory irritation. The red tide toxins can also accumulate in molluscan filter-feeders such as oysters and clams, which can lead to Neurotoxic Shellfish Poisoning in people who consume contaminated shellfish.
I spent last weekend on LGI (Little Gasparilla Island) and experienced the red tide up close and personal. We had a steady west wind with wave action rather than the glassy calm so often seen on the gulf coast. I now know these conditions were perfect for the respiratory irritation we all experienced
On Saturday, you could see the red tinge in streaks in Gulf waters. We escaped by boat to an intercostal sand bar but had to return to our cottage at day’s end. Although the sunsets were spectacular, we watched the last one from the safety of our cottage as you began to cough the moment you stepped out on the balcony.
My wife lost her voice and I suffered gastrointestinal symptoms in addition to the respiratory distress and skin irritation.
Monday morning we’re all back home safe and sound. The symptoms are slowly abating. We have been gargling with colloidal silver and taking Slippery Elm Bark to expel the toxins.
The Bottom Line:
Florida Red Tide is a fact of life for the west coast of Florida. Unlike most of the algae blooms, fresh water runoff from Big Sugar is not a major factor. Sure, the nutrients can feed the algae expanding the bloom, but the fresh water kills K. brevis. In my ignorance, I was too quick to blame our environmental mismanagement for the red tide. This one is a natural phenomenon.
Source: Florida Fish and Wildlife Conservation Commission