ABOUT RED TIDE ...

On a sultry Fall morning of 1947, the community of Venice, Florida, awoke to thousands of dead fish along the beaches and a stinging, choking "gas" in the air. Some blamed nerve gas, others a chemical spill, but scientists soon discovered the cause : RED TIDE. Although this was the first scientific documentation of this catastrophic event along the Florida Gulf coast, reports of similar events have been recorded as far back as the mid 1800's.

 Red tides occur throughout the world, drastically affecting Scandinavian and Japanese fisheries, Caribbean and South Pacific reef fishes, and shell fishing along U.S. coasts. Most recently, it has been implicated in the deaths of hundreds of whales, dolphins, and manatees in North American waters. These red tides are caused by several species of marine phytoplankton, microscopic plant like cells that produce potent chemical toxins. The Florida red tide is caused by blooms of a dinoflagellate that produce potent neurotoxins. These toxins cause extensive fish kills, contaminate shellfish and create severe respiratory irritation to humans along the shore.

 Florida red tide blooms typically begin in the Gulf of Mexico 40-80 miles offshore and move slowly southeast with the prevailing ocean currents toward the Tampa Bay area. As the bloom progresses, the density of red tide organisms increase to several million cells in each liter of sea water, and the effected area expands to many square miles. The result is a mass of deadly toxin containing water sweeping toward the southwest Florida coast, leaving a wake of dead and dying fish.

 As the bloom approaches the shoreline, we begin to see and feel the obvious effects: dead fish, the characteristic burning sensation of the eyes and nose, and dry, choking cough. When the bloom is severe, fish die rapidly from the neurotoxic effects of the red tide which enter their bloodstream through the gills. Because the fish die so quickly, these toxins do not have time to build up in their tissue. Fish exposed to lower (sub lethal) concentrations, however, may accumulate these toxins in their body. New evidence from current research suggests that such bioaccumulation in fish eaten by dolphins may have been a major factor in the deaths of more than 700 of these marine mammals in 1987.

 Red tide populations well below the fish kill level pose a serious problem for public heath through shellfish contamination. Bivalve shellfish, especially oysters, clams and coquinas, can accumulate so much toxin that they become toxic to humans. Public health concerns also emerge from studies that show the presence of airborne toxins have an impact on the human respiratory system.

 Because of the severe economic and public health effects of red tides, much consideration has been given to controlling the blooms. Control is only feasible within confined areas, such as fish hatcheries and aquaculture ponds, and research is underway to assess various control methods. Control in the broad expanses of the Gulf of Mexico, however, is neither feasible nor desirable at this time.
 
 

Although coastal pollution has enhanced red tide blooms in other areas of the world, the Florida red tides represent a natural process not caused by pollution. These blooms serve a purpose in the ecology of Florida Gulf coastal regions. Our responsibility is to understand the purpose and function of red tides, directing our efforts toward alleviating the adverse effects without causing further ecological damage.

 The more we learn about red tide, the more intriguing this natural phenomenon appears. There is much more to this than is detected by our eyes and nose. The red tide organism plays a very important role in the conversion of solar energy to chemical energy (photosynthesis), a process essential to the survival of all animals. Why this little menace also produces neurotoxin is still a mystery. Mote is dedicated to research that will help us, not only understand the natural and man made factors that influence red tide, but also to minimize and mitigate the health effects to humans and marine life.

THE FACTS:

WHERE DOES IT COME FROM? G. breve blooms are initiated miles offshore of the Florida Gulf Coast, moving onshore with winds and ocean currents. Scientists believe that G. breve algae may enter a dormant state at some point in their life cycle, forming cysts which settle miles off the west coast of Florida in ocean bottom sediments creating a "seed bed" effect. They think that strong flows of warm water from the Gulf Stream may carry the algae up the East Coast and inshore to the Carolinas.
 
 

HOW DOES IT AFFECT HUMANS? Irritations of the eyes, nose, throat, tingling lips and tongue are common symptoms that often occur during red tides. Waves, wind and boat propellers in high concentrations of red tides disperse toxin particles into the air causing these problems for people along the shoreline. People suffering from severe or chronic respiratory conditions such as emphysema or asthma, should try to avoid red tide areas. Symptoms usually disappear within 24 hours once the exposure is discontinued.
 
 

HOW DOES IT AFFECT MARINE LIFE? G. breve produces potent neurotoxins. Filter feeding shellfish, such as oysters, clams, mussels and other bivalve mollusks, that consume G. breve concentrate the toxin in various organs. Whereas red tide toxins are deadly to fin fish, shellfish are uneffected. These toxins also are incorporated into the marine aerosol, which causes the respiratory irritation to people along the shore.
 
 

Shrimp, Crab, Scallops and Lobsters in red tides are SAFE to harvest and eat, since these shellfish do not accumulate the red tide toxin in the meaty or hard muscle tissue which we normally consume. It is NOT a good idea to eat liver, organs, or other soft tissue of shellfish.

 The muscle or "hard" meat of freshly caught fin fish in red tides are SAFE to eat, provided the fish behave normally. Although no evidence of harmful effects in humans from contaminated fish have been reported, it is NOT a good idea to eat liver, organs or other soft tissues.

 Oysters, Clams, Mussels, Mollusks, Whelks are UNSAFE to harvest & eat since they may accumulate red tide toxins in their tissues. This remains effective until the Department of Environmental Protection determines that the waters are clear of red tide & shellfish are free of red tide toxins, which may take several weeks after a red tide bloom is over.

 Swimming & Enjoying the Gulf Beaches are fine for most people however, some people have reported skin irritation after swimming. However, respiratory irritation and fish kill are not always present during red tide outbreaks. Use common sense -- if the red tide bothers you, avoid the area. For current conditions along the Southwest Florida coast, check out the Red Tide Update page.