Algal Blooms

According to National Oceanic and Atmospheric Administration's (NOAA), harmful algal blooms, or HABs commonly refer to as red tide, are algae that grow very fast and can form dense populations or "blooms". A small percentage of blooms produce toxins or grow excessively, harming humans, other animals, and the environment.  This occurs when colonies of algae that live in the sea grow out of control.  Wave action can break open Karenia brevia cells and release these toxins into the air, leading to 

respiratory irritation.


There are three types of algae associated with red tides, Alexandrium fundyense found on the Atlantic coastline from New England into Canada, Alexandrium catenella common throughout the Pacific, and Karenia brevia found in the Gulf of Mexico, particularly along the coast of Florida and the Texas shore but has gone as far as North Carolina.


At high enough concentrations, Florida red tide can discolor water a red or brown hue. It doesn't always appear as a dark red and brown color, Karenia brevis can give a yellowish cast to the water at moderate levels. The water can also remain its normal color during a bloom.



When and Where Does Red Tide Occur?

Red tide takes place almost every summer along Florida's Gulf Coast, typically between July and October, although Karenia brevis is always present at low concentrations in the Gulf of Mexico. Most of the toxin blooms last a few weeks but can linger to a year or longer. They can even subside and then reoccur.  


Several factors can cause an algal bloom to grow. Low salinity, a high nutrient content in the water and warmer-than-usual surface water temperatures are usually cited as contributing to a red tide's formation.


The Florida red tide can be found in bays and estuaries but not in freshwater systems such as lakes and rivers. Because Karenia brevis cannot tolerate low-salinity waters for very long, blooms usually remain in salty coastal waters and do not penetrate upper reaches of estuaries. 



Is it Safe to Swim in the Water or Eat the Seafood?

No human deaths have been attributed to red tide or red tide allergy, however respiratory and skin and eye irritations have been reported. However, these symptoms usually subside after leaving beach areas. The Florida Department of Health advises people with severe or chronic respiratory conditions, such as emphysema or asthma, to avoid red tide areas. Offshore winds usually keep respiratory effects on the shore to a minimum.

 

Swimming is safe for most people. However, the Florida red tide can cause some people to suffer skin irritation and burning eyes. People with respiratory illness may also experience respiratory irritation in the water. It is advised that you get out of the water and thoroughly wash off if you experience any irritation. Avoid any areas with dead fish as they can carry harmful bacteria.


Store-bought and restaurant-served shellfish are safe to eat during a bloom because the shellfish are monitored by the government for safety. If harvested locally, they are tested for red tide toxins before they are sold.


Recreational harvested or illegally harvested shellfish are dangerous and should never be consumed during any closure of a shellfish harvesting area. To determine whether if harvesting of shellfish is permitted in an area, visit the Florida Department of Agriculture and Consumer Services, Division of Aquaculture website.  


It is okay to eat local finfish as long as the fish are filleted before eaten. Although toxins may accumulate in the guts of fish, these areas are disposed of when the fish are filleted. 


Keep in mind that the toxin cannot be seen or tasted and cooking or freezing will not destroy the red tide toxin. 



Will Florida red tide affect my pets?


Pets may be affected by the Florida red tide. The algae linked to red tides contain a toxin that affects the nervous and digestive systems of animals. Red tides are usually accompanied by a massive die-off of fish, 

as well as the birds and other animals that feed on fish.  If you live close to the beach, consider bringing outdoor pets inside during a bloom to prevent respiratory irritation. Do not allow them to play with dead fish or foam that may accumulate on the beach during or after a red tide.  


If your pets swim in red tide, rinse them off as soon as possible to prevent them from licking any of the toxins from their fur.


Although the occurrence of a red tide cannot be predicted, scientists can forecast its movement using wind and water current data once a bloom is located. Scientists also monitor the concentration of the red tide organism by collecting water samples routinely and in response to blooms. 


Before planning a trip to the beach, visit NOAA's tides and currents forecast. It provides an overview of the Gulf, forecasts, and links to state sites with more information.



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