What are harmful algal blooms (HABs)?

Q: What are harmful algal blooms (HABs)?

A: When algae grows quickly, it’s called a “bloom.” Blooms can become large and dense, shading seagrasses and causing it to die off. Blooms can also deplete the oxygen in the water, emit gasses, and produce toxins. HABs are generally caused by one of three different types of phytoplankton: dinoflagellates, diatoms, and cyanobacteria.

Q: What causes a harmful algal bloom?

A: HABs are the product of environmental conditions. Abundant nutrients such as nitrogen and phosphorus, washed into waterways via farm runoff, urban runoff and leaky septic tanks are a key factor, as are warm temperatures, sunlight, slow-moving water and stable wind conditions. Lake Okeechobee water discharges also contribute to HAB conditions along the Caloosahatchee River, St. Lucie River, Indian River Lagoon, and Lake Worth Lagoon.

Q: Are there different types of harmful algal blooms?

A: Two main types of HABs cause problems in Florida:

Cyanobacteria, also called blue-green algae; these blooms devastated the northern estuaries in 2013, 2016 and 2018.
Dinoflagellates are a cause of red tide, which impacted Florida’s west coast in 2018 and 2022-23.

In addition, high levels of another type of toxic algae, cylindrospermopsin, was detected in the West Palm Beach drinking water supply in 2021.

Q: What are cyanobacteria?

A: Cyanobacteria are microscopic organisms that occur naturally in freshwater, salt/marine water and brackish water (a mix of fresh and saltwater). They are photosynthetic, meaning they can manufacture their own food; in warm, nutrient-rich environments they can multiply rapidly, creating massive blooms. Some freshwater blooms produce cyanotoxins, which can be extremely toxic and dangerous to people, pets and wildlife.

Q:What is red tide?

A: In saltwater environments, red tide is caused by Karenia brevis, a microscopic algae that produces highly potent toxins called brevetoxins, that can kill fish and other marine life, and cause harm to humans. As with cyanobacteria, they can grow rapidly, causing massive blooms. While they occur naturally, and have been documented along coastal Florida as far back as the 1700s, increased nutrient pollution/runoff contributes significantly to today’s blooms.

Q: What are the health effects of harmful algal blooms?

A: Exposure to the cyanotoxins in cyanobacteria can cause a variety of short-term symptoms including skin irritation, headache, sore throat, muscle and joint pain, stomach cramps, vomiting, nausea and diarrhea and mouth blisters. Longer-term effects can include liver and kidney damage. New studies suggest cyanotoxins may be linked to neurodegenerative diseases like Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis, known as ALS/Lou Gehrig’s Disease.

Red tide can cause irritation of the eyes, nose and throat; the symptoms are usually temporary.

Both cyanobacteria and red tide can be fatal to marine life, and blue-green algae can kill dogs and other mammals.

Q: How does the management of Lake Okeechobee expose citizens to harmful algal blooms?

A: When water is discharged to the St. Lucie and Caloosahatchee rivers and Lake Worth Lagoon, it delivers significant amounts of nutrient pollution to both estuaries, fueling algae blooms. When existing blue-green algae blooms in the fresh lake water is discharged into the normally saline estuaries, it creates conditions favorable for those blooms to both survive and grow in intensity. HABs that originate in Lake Okeechobee are sometimes physically transmitted to these estuaries during high-lake conditions, when the Army Corps of Engineers opens floodgates to draw down lake levels in the name of flood control. The new Lake Okeechobee System Operating Manual, scheduled to take effect in late 2023, acknowledges the risks of toxic algae in lake-management decisions and incorporates flexibility to mitigate the risk of exposure.

Q: What is the state of Florida doing about HABs to protect the public?

A: Not nearly enough. The Florida Legislature has allocated millions of dollars to study the problem, and funded “innovative technologies” to clean up and mitigate blooms. Enhanced water-quality monitoring seeks to better identify HABs. And in recent years the state has stepped up spending on and legislation encouraging septic-to-sewer conversions. Unfortunately, many efforts have fallen short. Gov. DeSantis created the Harmful Algal Bloom/Red Tide Task Force and Blue-Green Algae Task Force in 2019, but the Legislature has ignored most of the task force recommendations.

Q: How can we get rid of harmful algal blooms?

A: Experts say nutrient pollution must be drastically reduced to curtail the conditions that produce HABs, yet the Florida Legislature has shown little appetite to crack down on politically powerful polluters. “Legacy” nutrients in the muck at the bottom of key water bodies will continue to feed blooms. Ultimately the “answer” to HABs in Florida is multi-faceted, involving more water treatment and storage south of Lake Okeechobee, strict new pollution regulations on agricultural polluters, the completion of key water quality projects in the Everglades and elsewhere throughout Florida, more septic-to-sewer conversions and limits on new septic systems in sensitive areas, new requirements on the application of biosolids in vulnerable watersheds, and more.

Q: How does the sugarcane industry contribute to the HABs crisis in Florida?

A: State policymakers have protected the water interests of large sugarcane growers that use Lake Okeechobee as a de facto reservoir for cane fields in the Everglades Agricultural Area. Lake Okeechobee is kept artificially high during the dry season to ensure plenty of water for sugar farmers to irrigate the estimated 440,000 acres of sugarcane south of the lake.

During the rainy season, drainage capacity in the taxpayer-funded stormwater treatment areas (STAs) has historically been prioritized for sugarcane runoff instead of water from Lake Okeechobee. With little capacity to send Lake O water south, the Army Corps of Engineers (in consultation with state water managers), sends polluted, algae-carrying discharges from Lake Okeechobee to the St. Lucie and Caloosahatchee estuaries and Lake Worth Lagoon.