Sunday, November 28, 2021

Red Tide – Marco’s in bloom

Karenia brevis.

Karenia brevis.

Nancy Richie

Marco Island is currently experiencing a red tide event caused by a harmful algae bloom (HAB) of the algae species, Karenia brevis. Karenia brevis is a microscopic algae species that naturally occurs in the Gulf of Mexico and Florida Atlantic Ocean waters. The “bloom”, or a higher than normal amount or concentration of this algae in the water, creates decreased dissolved oxygen in the water, immediately causing fish to die and wash ashore onto the beaches and float in the bays and canals. The higher than normal concentrations of Karenia brevis in the water also has caused mild complaints of upper respiratory irritation by beach goers and islanders. The irritation is a result of the neurotoxins released by Karenia brevis into the air. The neurotoxins, in this case called brevetoxins, if produced at very high concentrations, can cause damage to nerve cells or tissues and can kill a large number of shellfish, fish and other marine animals as well. The concentrations of Karenia brevis offshore Collier County and in the inlets and passes of Marco Island have been in the low to medium ranges which have caused the outcome we are experiencing for the past two weeks. The winds are helping to keep most of the impacts offshore, but unfortunately, the dead shellfish and small fish arrived in high numbers, still lingering in some waterways of the island. In the past couple of weeks, many residents, especially if boating south of Marco Island in the 10,000 Islands, have noted the thousands of Black Vultures circling, hunting and doing their job as the “waste management” of the Everglades by feeding on the fish carcasses.

The effects of Florida’s red tide were first recorded in the logs of Spanish sailors and explorers and is seen in coastal Florida somewhere almost every year. As the population of Florida grows, more awareness and impact (aesthetically, physically and economically) from red tide grows, too. If a bloom lasts for an extensive period of time or it has very high concentration of the algal species, public health is at risk as well as the economy that is dependent on tourism and fisheries. With these impacts in mind, the Florida Fish and Wildlife Commission’s Fish and Wildlife Research Institute (FWC-FWRI) directed $1,000,000 each year between 2007-2009 to find environmentally acceptable technology to control Karenia brevis blooms and the effects they have on Florida. Grants issued with this money, created twelve projects that specifically addressed red tide in Florida, including alleviating human health impacts; economic impact studies; investigating biological, chemical or physical control of blooms and/or their toxins and outreach and education strategies for coastal communities. Though some projects are ongoing, many projects have halted due to budget cuts.

One of the most current and helpful projects that was created is the Beach Conditions Reporting System by Mote Marine Laboratory. It is “real time” reporting of beach conditions by park rangers and volunteers, twice a day. Wind direction, surf status, respiratory irritation, and water color are reported and recorded for beach goers who can access the information in “real time” via a hotline (941-BEACHES) or website ( This allows beach goers to make informed decisions on which beach to visit with minimal exposure to red tide. Since 2008, on Marco Island, the Collier County Park Rangers give reports at Tigertail Beach, South Beach and Caxambas Pass locations twice a day, 365 days a year.

There are also ongoing, hopeful studies of biological controls regarding the toxicity of Karenia brevis being conducted at the Georgia Institute of Technology (GIT) and by the Smithsonian Institute. The study at GIT has a goal to identify which phytoplankton (microscopic plant organisms naturally present in the waters) can be a natural biological control of Karenia brevis toxicity and whether the phytoplankton could also benefit other marine life. The Smithsonian study is looking at micro parasitic species that could be introduced to red tide blooms to control and shorten the bloom.

As an islander and coastal resident of Florida, one of the most important factors to remember to contribute to the control and mitigation of red tide blooms in the coastal waters is to know what is being applied to your yard and swales. Nutrient introduction to the surface waters from run off from yards and streets can contribute to more intense and longer lasting red tide blooms. Following Florida Friendly Landscape best management practices and principles by planting the right plants in the right place, using minimal fertilizer and chemicals, and conserving water, all contribute to improved water quality in the adjacent water bodies.

Important Information: To report dead fish or red tide symptoms, please call the Collier County Pollution Control and Prevention Dept. at (239) 252-2502. To speak to a health professional anytime, toll free, call the Aquatic Toxins Hotline at 1-888-232-8635. Collier County Red Tide Updates are also available on the Red Tide Hotline at (239) 252-2591. This is an automated recording with the most recent Red Tide information for Collier County available 24 hours a day, 7 days a week.

For more information on red tide or Florida Friendly Landscape, please contact Nancy Richie, Environmental Specialist, City of Marco Island, at 239-389-5003 or

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