What is cyanobacteria and why is it a problem for irrigation systems?

Cyanobacteria — commonly known as blue-green algae — are microscopic organisms that form large blooms in freshwater bodies. For irrigation systems, they present two main risks: some species produce toxins (including liver-damaging hepatotoxins and nerve-damaging neurotoxins), and the algae itself can physically clog pipes, sprinkler heads, filters, and pump inlets. Because individual cyanobacteria are small enough to pass through many filter types, a bloom in an irrigation lake can infiltrate a system before it becomes visible to the naked eye.

How do I know if my irrigation lake has cyanobacteria?

A visible blue-green bloom or surface slime on the lake is the most obvious sign — but by that stage cyanobacteria have likely already entered the irrigation system. The only reliable way to confirm their presence, and whether toxic strains are involved, is water testing. The EPA lists several Florida laboratories that can test for cyanobacteria and cyanotoxins, including GreenWater Laboratories in Palatka, Everglades Laboratories in West Palm Beach, and Jupiter Environmental Laboratories in Jupiter.

How do you treat cyanobacteria in an irrigation lake?

There are three main treatment approaches. For system components (pipes, filters, sprinkler heads), manual cleaning with a hydrogen peroxide solution is recommended — it has an oxidising effect on cyanobacteria. For the lake itself, algaecides can kill a bloom quickly but are controversial: Florida data shows that 92% of lakes treated with algaecides in August 2023 saw a bloom recur post-treatment, and 32% still had toxicity above safe limits. Ultrasound devices are a chemical-free alternative; independent research has shown they can reduce algae by 80–90%, though results vary by algae type and device.

What causes cyanobacteria blooms in Florida irrigation lakes?

Blooms are primarily triggered by excess nutrients — particularly nitrogen and phosphorus — in the water. Common sources include fertiliser and pesticide runoff from surrounding land, stormwater carrying grass clippings and organic waste, agricultural and urban wastewater, and legacy nutrients already present in lake sediments. Florida's warm temperatures, seasonal rainfall patterns, and long coastline make it one of the global epicentres of Harmful Algal Blooms. Climate change factors — including warming water temperatures and increasing hurricane severity — are thought to be intensifying the problem.

How can I prevent cyanobacteria in my irrigation lake?

Prevention focuses on controlling nutrient levels in and around the lake. Test water regularly to keep phosphorus and nitrogen within healthy ranges; if levels are elevated, specialists can use products like Alum or Phoslock to rebalance them. Aeration — through a submerged pump or surface fountain — helps circulate oxygen and discourages bloom formation. Around the lake's edge, avoid fertilising right up to the shoreline and use phosphorus-free products where possible. Creating a buffer zone of dense turf or native plantings 3–6 feet from the water's edge helps absorb runoff before it reaches the lake.