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Frequently Asked Questions

Contact us if you have questions about algae or harmful algal blooms not included below.

Algae are a large and diverse group of organisms that use the sun’s energy to grow through photosynthesis, just like plants.

Algae can be found all over the world on land and in the water. Aquatic algae live in freshwater environments like lakes and rivers and saltwater environments like estuaries and the ocean.
Algal blooms are a rapid overgrowth of algae that cause the water to become discolored and thick with algae. Algal blooms can occur naturally and can be beneficial to the ecosystem. However, harmful algal blooms can have negative impacts on ecosystems and people's health.
Harmful algal blooms (HABs) can appear as floating scum, slime, or mats on the surface of the water. They can also discolor the water, from shades of red to brown or blue to green. Toxins from HABs may be present in the water even if the water appears clear.
Algae occur naturally in bodies of water and are an essential component of most aquatic ecosystems. Harmful algal blooms occur when environmental conditions support excessive amounts of algae growth. Ample levels of nutrients such as nitrogen and phosphorus plus favorable weather conditions are necessary for many kinds of algal blooms to form. The exact conditions that trigger an algal bloom are difficult to pinpoint because they are complex and driven by a combination of natural and human influences that make it difficult to predict when a bloom will occur. Video 3. What Are Algal Blooms?  examines the causes of algal blooms.
Algal blooms have been occurring for thousands of years, but the recent rise in documented cases of algal blooms may be linked to increased nutrients from human sources. Excess nutrients including nitrogen and phosphorus can be introduced to bodies of water from agriculture runoff, residential runoff, and septic tanks. Video 3. What Are Algal Blooms? includes more information on sources of nutrient pollution.
Harmful algal blooms (HABs) occur in freshwater, estuarine, and saltwater environments throughout the country, including Hawaii and Alaska, as well as around the globe. HABs occur throughout Florida from the west coast to the east coast and Lake Okeechobee. This map shows the current status of algal blooms in Florida.
Because harmful algal blooms (HABs) require warm temperatures and sunlight, HABs usually occur during the warmer parts of the year when water temperatures are higher and the days are longer. However, HABs can occur year round, especially in warmer climates like Florida.
Harmful algal blooms (HABs) are not a new problem. One of the earliest anecdotal reports of harmful algal blooms comes from the Han Dynasty more than fifteen hundred years ago. However, the documented cases of algal blooms is on the rise. Researchers are examining why HABs appear to be occurring more frequently.
Harmful algal blooms (HABs) can have a wide range of impacts on people’s health, the economy, and ecosystems. Toxins produced by HABs can have minor to life-threatening health effects in people and animals. The increased costs associated with HAB events may be in the billions of dollars including medical expenses and loss of business. HABs can also be detrimental to aquatic ecosystems even without the production of toxins. The impacts of harmful algal blooms are covered in Video 4. Impacts and Examples of Harmful Algal Blooms.
Only some species of harmful algal blooms (HABs) produce toxins. The type of toxin produced also varies with HAB species. HABs and toxins production are discussed in Video 4. Impacts and Examples of Harmful Algal Blooms (HABs).
Toxins produced by harmful algal blooms (HABs) can have minor to life-threatening health impacts. Different types of toxins can affect specific systems within the body. For example, neurotoxins affect the nervous and respiratory systems, dermatotoxins affect the skin, and hepatotoxins affect the liver. Toxins can have a wide range of health impacts. Contact with the water can cause skin irritation; breathing in water droplets can cause respiratory irritation; and ingesting the toxins can cause gastrointestinal issues, liver damage, and neurological symptoms. Toxins can have more serious health effects in people with preexisting conditions. View the Resources Page to learn more about the health effects of HAB toxins.

Warmer temperatures will likely increase the frequency and severity of harmful algal blooms (HABs), especially if high nutrient levels are present. Increased extreme weather events including droughts and high precipitation events can also provide favorable conditions for HABs. View the Resources Page to learn more about the effects of climate change on HABs.

Removing all the algae in a large body of water is nearly impossible and would be detrimental to the aquatic ecosystem. Algae are a natural and essential component of most aquatic ecosystems because they are a food source for many species. Algae also produce large amounts of oxygen in our atmosphere through photosynthesis.
There is still much more to learn about preventing and managing harmful algal blooms (HABs). While much is known about the science behind algal blooms, there are still many unknowns about how we can prevent them and manage them during harmful algal blooms or HAB events. Reducing nutrient pollution is one way to help reduce the frequency and intensity of future harmful algal blooms (HABs), especially as global temperatures increase. There are many different methods to reduce nutrient pollution from agricultural runoff, residential runoff, septic tanks, and other sources. You can learn more about reducing nutrient pollution in Video 5. What Can We do About Harmful Algal Blooms (HABs).
Check your local advisories for beach closures and follow all beach closure signs. You should also avoid the water if you seen signs of a harmful algal bloom including discolored water and dead fish.

Avoid the area if you find signs of a harmful algal bloom (HAB) or if the beach is closed. Toxins may be present in the water and in the air surrounding the water. You and your pets should not swim, drink, or eat anything from the water. If you or your pet becomes ill, contact a healthcare provider or veterinarian. You can check for beach closures or report algal blooms to your local advisories or state departments of health/environment.

View our Understanding Algae in Florida Videos to learn more about algae and harmful algal blooms. Check out the Resources Page to learn more about specific topics. You can also contact us to ask an expert if you need more information.

 Last Modified 4/3/23