Red Tide Frequently Asked Questions
What Is Florida Red Tide?
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
Do Red Tides Occur Anywhere Else?
Yes. Although the organism that causes Florida's red tide is found almost exclusively in the Gulf of Mexico, blooms have been found off the east coast of Florida and a bloom was detected off the coast of North Carolina in 1987. 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 or HABs) in other parts of the world as well. HABs occur in both saltwater and freshwater.
How Long Does Red Tide Typically Last?
It can last days, weeks, months and it can change daily due to wind conditions. Thus, contact your local area for accurate and current conditions.
Is Red Tide a New Phenomenon?
No. The first official reporting of red tide in Florida was in 1844. Government officials documented discolored water and massive fish kills.
What Conditions Cause Red Tide?
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 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.
Is It Safe to Swim During a Red Tide?
Yes, for most people. However, for 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.
How Is Red Tide Related to Respiratory Irritation?
People experience respiratory irritation (coughing, sneezing and tearing) when red tide organism (Karenia brevis) is present along a coast and winds blow its toxic aerosol on shore. CAUTION: People with severe or chronic respiratory conditions (such as bronchitis, emphysema or asthma) are cautioned to avoid red tide areas.
Generally, symptoms are temporary and disappear within hours (once exposure is discontinued). Most people find air-conditioned facilities decrease symptoms quickly. Since the red tide toxin is particulate matter when airborne, wearing a particle filter mask may lessen effects while on the beach.
Is It Safe to Eat in Restaurants During a Red Tide?
Yes. Commercial seafood from local restaurants and grocery and seafood stores must be harvested from red tide free waters. This includes shellfish.
Can I Fish for Seafood During a Red Tide?
Yes and No! Shellfish must be avoided. There has been no reported human illness from eating filleted fish caught during a red tide.
Is It Okay to Eat Shellfish During a Red Tide?
No. If a shellfish-harvesting ban is in effect, it is not safe to eat mollusks (e.g. 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.
What Shellfish Are Included in a Shellfish-Harvesting Ban?
Harvesting of bivalve mollusks such and clams, oysters and coquinas is banned during red tides.
Is It Okay to Eat Fish, Crabs or Shrimp During a Red Tide?
Yes, because the toxin is not absorbed in the edible tissues of these animals. However, use common sense! Harvesting distressed or dead animals is not advised regardless of the cause of death or distress.
Does Cooking Destroy the Red Tide Toxin?
No.
Summary
It is important to realize that many people still enjoy the beaches during red tides. Respiratory irritation and dead fish are not always present.
Reprinted with permission from The Red Tide Alliance.
