Spring – a time for blooms of many kinds


Spring brings blooming flowers, frequent rainfall, and often – a subsequent increase in algal blooms in our lakes. Algae blooms have been around for billions of years, but blooms today are increasing in intensity, frequency, and duration as a direct result of human activity, population growth, and climate change. Lately, it seems these ‘algal’ bloom events are making the news from the Great Lakes to Florida and beyond. Many people find this information confusing and hard to understand – and for good reason.
Ironically, harmful algal blooms are not caused by true algae. Harmful algal blooms, or HABs, is a catch-all term used to define a sudden production of microorganisms called cyanobacteria, or blue-green algae. Cyanobacteria are the oldest organisms on earth, and their presence dates to 3.5 billion years. HABs can occur in oceans, lakes, rivers, streams, and estuaries – even in polar regions of the planet. (Cyanobacteria are not associated with red tide, though. Dinoflagellates are another type of microorganism responsible for red tide that occurs in coastal areas.)


Cyanobacteria thrive in warm nutrient-rich waters, produce oxygen in our atmosphere that we need to breathe, help plants grow, serve as food for humans in some parts of the world, and play a critical role in fertilizer and oil production. And, these highly specialized but primitive organisms can adjust their buoyancy in the water column, turn on and off toxin production, and even produce ‘sunscreen’ to protect from damaging ultraviolet rays from the sun making them exceptionally resilient and complex.
The reason why they make the news, though, is that cyanobacteria can and do produce toxins – some of which are harmful to humans, pets, and wildlife, and these toxins have top of the food chain effects when they accumulate in prey species. The toxins can and do damage neurologic and respiratory systems, cause liver impairment, and damage muscle and skin tissues. Toxins are not able to be detected visually, and our body of knowledge surrounding HABs is growing significantly, so that means we will be hearing more about them.


Cyanobacteria are a natural part of every lake and wetland system, and they are a critical part of the food chain. However, under certain environmental conditions, these cells multiply rapidly and a ‘bloom’ occurs. Cyanobacteria prefer waters that are warm, shallow, calm, and where there is plenty of sunlight and nutrients. When a cyanobacterial bloom is present, the water may resemble pea soup, or it may look like someone has dumped brightly colored paint into the water. The presence of cyanobacteria alone does not mean the lake is hazardous, so testing is necessary to determine if the bloom is producing toxins. Toxins cannot be confirmed with a visual inspection.

What should I do if I suspect a bloom?

If you see a suspected bloom on your lake, refrain from irrigating, swimming, and recreating until the water has been sampled. It is important to keep pets away from the water during this time as well.


The Florida Department of Environmental Protection (FDEP) monitors and responds to reports of suspected blooms. Once a report is made, staff will respond and collect a sample for testing to determine if a toxin is present and if an advisory needs to be placed on that waterbody. If a toxic bloom is confirmed, the Florida Department of Health (FDOH) and Orange County Environmental Protection Division (EPD) will send out an advisory. Residents and visitors can report potential blooms here.

In addition, you can sign up to receive weekly updates from FDEP here.


Register for EPD’s Advisory Notices here.

How can I reduce my risk of exposure?

Toxins from HABs can be problematic when ingested, inhaled, or in direct contact with skin.

  • Ingestion – Keep an eye on kids and pets to prevent them from ingesting water while swimming. Remember, that pets will tend to groom their fur after swimming, and that can be a source of ingestion if a toxin is present. Toxins can accumulate in and sometimes concentrate in the tissues of fish, so it is always important to check on the status of a waterbody before fishing for consumption.
  • Inhalation – If a bloom is present, refrain from spending time in or on the water recreating. Certain species of cyanobacteria produce toxins that become airborne and cause respiratory distress when inhaled.
  • Direct contact – It is always best to wash with soap and tap water after swimming in any surface waters. The same is true for pets and their water toys.

What can we do to get rid of HABs?

Cyanobacteria are a natural and essential part of the community of microorganisms in a lake, so they cannot be ‘removed’ or removed with chemicals. However, by reducing nutrient pollution (nitrogen and phosphorus from fertilizers, pet waste, grass clippings, landscape debris, etc.) and making sure that lakes have plenty of submersed, floating, and emergent native plants present, we can help minimize the conditions that cause HABs to form. Plants and vegetation not only take up nutrients that would otherwise fuel cyanobacterial growth, but they also provide shade which cools water temperatures and makes it harder for HABs to occur.


Orlando gets >75 M tourists annually and with an economy based on recreation, eco-tourism, and fishing, there is a lot of interaction with our lakes. Orlando’s population was 3x greater in 2010 than in 1960, and Central Florida’s population is growing at an alarming rate. Even as cities and counties work to mitigate the impacts of this growth, technology for HAB mitigation is lagging population increase. Florida has sandy soil, septic tanks, an abundance of pavement and sunlight, increasing temperatures, and plenty of water. We have to all work to suppress and reduce our nutrient footprint and hopefully keep these HABs at bay.

Additional resources:

Orange County, FL – EPD Concerned about Algae
FWC Cyanobacteria, Redtide
Florida Health – Aquatic Toxins


March outreach submitted to Town of Windermere
Text and photos by Amy L. Giannotti, MS, CLM, AquaSTEM Consulting, LLC


Amy L. Giannotti, MS, CLM, (amy@aquastemconsulting.com) is the founder of AquaSTEM Consulting, LLC – an environmental consulting company specializing in lake and aquatic plant management, aquatic habitat restoration, and science outreach initiatives. Amy is an Environmental Scientist and Certified Lake Manager and has over 20 years of experience working in marine and freshwater systems, including coastal and freshwater vegetation dynamics, exotic species management, impacts of nutrient enrichment and remediation efforts, stormwater management and watershed hydrology, and public speaking on environmental issues affecting lakes, estuaries, springs, and karst community ecology. Amy has a Bachelor of Science degree in biology from Marietta College, and she earned her Master of Science degree in Environmental Sciences from the University of Virginia. She is currently serving as the Town of Windermere’s Lakes Management Consultant.