Algae are plant organisms that support marine life. They contribute to the food chain and oxygen that keep bodies of water healthy, but sometimes when conditions are right – often warm water and more nutrients – some algae can quickly grow and overpopulate .
These masses of foam or foam are called blooms and can be pushed ashore by winds, waves, tides and currents. Some flowers release toxins that make ecosystems, animals and people sick. Scientists call these harmful algal blooms, known as HABs. In Florida, HABs can be found in our saltwater, freshwater, and brackish bodies.
HABs usually occur in summer or early fall and can affect small and large areas of a body of water. Blooms can move and change in a body of water due to tides, winds and naturally fluctuating amounts of algae. Even if a specific location does not bloom constantly, the flowering itself may continue for weeks, months, or more than a year.
As some HABs decompose, they give off a bad odor due to hydrogen sulfide, a foul-smelling gas that is a natural, colorless decomposition product. It may smell like rotten eggs. The human nose is very sensitive and can smell the unpleasant odor of hydrogen sulfide at very low levels.
The Florida Department of Health conducted tests in 2016 and 2018 to detect the presence of hydrogen sulfide in the air during HAB events. The results of both studies indicated very low levels, non-hazardous levels. The odor may cause respiratory tract irritation, but is not harmful to health.
- If you are irritated by the strong odor or have difficulty breathing, move away from the source of the odor.
- Symptoms should disappear shortly after the odor disappears or exposure to the odor ends.
Animals can also be affected by harmful algal blooms. For more information available to veterinarians and pet owners, see Education and Resources.
There are many species of HAB in the Gulf of Mexico. Karena Short (K. brevis), a naturally occurring single-celled organism belonging to a group of algae called dinoflagellates, is the common cause of red tide in Florida.
Red tide can discolor water and make it appear red or brown, and it produces powerful neurotoxins, called brevetoxins, which can be harmful to the health of people and animals. Brevetoxins can be released into the air or water when wind and waves break down algae cells. Respiratory irritation may occur upon exposure to brevetoxins.
Health impacts
Even if you are not prone to respiratory problems, remain careful. Red tide can cause coughing and sneezing and irritate the eyes, nose and throat. Reactions to red tide may be worse in people with asthma, emphysema, bronchitis, or any chronic lung disease.
- You can relieve respiratory symptoms by being in an air-conditioned space.
- For people without asthma or chronic breathing problems, over-the-counter antihistamines can help.
If your symptoms do not improve, contact or consult a doctor or call the Florida Poison Information Center at 1-800-222-1222.
Avoid exposure
Do not swim in or around red tide, as the toxin can cause skin irritation, rashes, burns and eye pain. If you come into contact with red tide, rinse with soap and water, especially if your skin is easily irritated.
The fish kills
Red tides can kill fish and other marine life. Avoid areas where dead fish can be seen – do not swim or walk in these areas. Additionally, keep your pets away from these areas.
Consume fish
Do not harvest or eat distressed or dead fish (or other animals) because of or near red tide.
Fish caught alive and healthy can be eaten if cut into fillets and rinsed thoroughly in fresh water.
Consume shellfish
Check local harvest status on Florida Department of Agriculture and Consumer Services.
Bivalve molluscs, including clams, oysters, mussels and scallops, are filter feeders that can concentrate toxins. These and other shellfish, if harvested in red tide areas, can be contaminated with brevetoxins. The scallop muscle is generally free of toxins, but the rest of the scallop is not. Marine gastropods, commonly called sea snails (conch, whelk, etc.), feed on bivalves and can also be contaminated with brevetoxins during a red tide.
Your safest choice is not to harvest or eat marine molluscs or gastropods in areas affected by red tide.
You could suffer from neurotoxic seafood poisoning (NSP) if you eat contaminated seafood. Symptoms of NSP include:
- Nausea and vomiting
- Tingling in the mouth, lips and tongue
- Troubled speech
- Dizziness
Neurological symptoms can progress to partial paralysis and breathing problems.
There are severalthe species of bread-green algae (also known as cyanobacteria) which can be found in fresh or brackish bodies of water in Florida., many of which have the potential to produce toxins.
If people or animals splash in the water or boats create wakes, algae cells can be broken and cyanotoxins can be released into the air. The toxins mix with water droplets and sprays, causing people and animals to inhale the toxin.
Although contact with algae can cause skin irritation, these toxins cannot easily pass through your skin, so ingesting large amounts of contaminated water can usually cause illness.
Blue-green algae blooms can be described as discolored water in a variety of colors such as blue, bright green, brown or red, and appear as paint-like streaks on the surface water, dense scum or foam which can emit unpleasant odors.
Health impacts
For some people, exposure to blue-green algae can cause skin rashes, stomach cramps, nausea, diarrhea, and vomiting. People who are very sensitive to odors may experience respiratory irritation. Sometimes high exposures to toxins can affect the liver and nervous system.
Pets can get sick from blue-green algae, so keep them out of these areas and away from contaminated marine animals and fish.
If you come into contact with blue-green algae or think that blue-green algae has made you sick, contact your health care provider or call the Florida Poison Information Center at 1-800-222-1222.
Avoid exposure
Water from areas with blue-green algae can make people and animals sick, so it is advisable to stay away from these areas.
Do not cook or clean dishes with water contaminated with algae blooms. Boiling water will not remove toxins.
Do not swim in or around blue-green algae. If you come into contact with blue-green algae, rinse with soap and water, especially if your skin is easily irritated.
Consume fish
Fish tested in waters containing blue-green algae show that cyanotoxins do not accumulate significantly in the edible parts (muscle or fillet) of the fish but can do so in other organs.
Before eating, rinse the fish fillets in tap or bottled water, discard the guts and cook the fish thoroughly.
Do not eat shellfish in waters where blue-green algae grows.