A red tide is a higher-than-normal concentration of a microscopic alga (plant-like organisms). In Florida, the species that causes most red tides is Karenia brevis.
This organism produces a toxin that can affect the central nervous system of fish. At high concentrations (called a bloom), the organisms may discolor the water. However, red tides are not always red. They can appear greenish, brownish and even purple in color. Or, the water can remain its normal color.

Red tides have been reported worldwide from China, the Pacific Northwest to the Atlantic Northeast in the USA. The organism that causes the Florida red tide is found almost exclusively in the Gulf of Mexico, blooms have been found off the east coast of Florida and coast of North Carolina. Scientists believe the Florida Current and Gulf Stream Current carried Karenia brevis out of the Gulf of Mexico, around South Florida and up to the Carolina coast. Other types of microorganisms cause different kinds of red tides (now called harmful algal blooms) in other parts of the world as well.

No. The first official reporting of red tide in Florida was in 1844. Government officials documented discolored water and massive fish kills.

A red tide outbreak usually lasts several months but is sporadic and patchy. Blooms have, under more unusual situations, lasted for more then one year.

The red tide organism, Karenia brevis, is a part of the Gulf of Mexico ecosystem and can be found in low concentrations at any time. Blooms or red tides occur when very high concentrations of red tide cells occur. Blooms are most likely to occur from August through November although there have been red tides in every month of the year. Scientists are working to develop a complete understanding of the physical, chemical and biological parameters that lead to red tide’s formation and persistence. Parameters such as temperature, salinity, currents, nutrients and competing species all may contribute to bloom conditions. One recently published theory regarding bloom initiation involves the transport of iron on dust particles from the Sahara desert (Walsh and Steidinger, 2001). The iron is essential to growth of the blue-green alga, trichodesmium. It is thought that trichodesmium, through its cellular activity, provides nutrients needed for the Florida red tide organism to grow. Scientists continue to collect data to in an attempt to validate this theory.

Walsh, J. J. and K.A. Steidinger, 2001. Saharan Dust and Florida red tides: The cyanophyte connection. Journal of Geophysical Research 106:11597-11612.

Not yet, but we are working on it! Both Mote Marine and FMRI takes samples of water off the gulf coast searching for red tide and report it weekly on the FRMI web site. The RTA hopes that the predictability of red tide will be accomplished through further research depending upon continued funding from the public/private sector.

CAUTION: People with severe or chronic respiratory conditions (such as emphysema or asthma) should consult their physician as to whether or not to avoid red tide areas during times of outbreaks. Use common sense.

Generally, symptoms are temporary and disappear within hours (once exposure is discontinued).

It is OKAY to eat fish, crabs and shrimp during a red tide because the toxin is not absorbed in the edible tissues of these animals. However, regardless if red tide is in the area, eating distressed or dead animals is discouraged; the cause of the organism’s strange behavior or death cannot be absolutely known. The cause of an organism’s dealth could be something unrelated to red tide.

If a shellfish ban is in effect, it is not safe to eat mollusks ( eg. clams and oysters) and gastropods that feed on bivalves (e.g. whelks). However, edible parts of other animals commonly called shellfish (e.g. crabs, shrimps and lobsters) are not affected by the red tide organisms and can be eaten. Scallops are ok to eat as long as you only eat the muscle of the scallop, do not eat whole animals.

Seafood purchased in local restaurants and grocery stores is safe to eat as all commercial seafood must be harvested from red tide free waters.

Cooking DOES NOT destroy red tide toxin.

Yes, for most people. However, in some people, red tide can cause skin irritation and burning eyes. Use common sense-if you are particularly susceptible to irritation from plant products, avoid red tide water. If you experience irritation, get out and thoroughly wash off. Do not swim among dead fish because they can be associated with harmful bacteria.

It is important to realize that many people still enjoy the beaches during red tides. Respiratory irritation and dead fish are not always present.