Blue-Green Algae Is More Than Ugly Water

On July 23, a dog died shortly after swimming in a slow, stagnant pool connected to California’s Eel River. Humboldt County health officials quickly warned residents to keep children, pets, and livestock away from water containing algae mats or scum. The county had issued a similar warning in 2024 after two dogs died shortly after swimming in another section of the Eel River. 

These were not industrial waste sites or remote bodies of water. They were the kinds of rivers, lakes, ponds, and reservoirs where families swim, fish, paddle, and let their dogs cool off on a hot afternoon.

Yet many people still see blue-green algae as ugly water, a seasonal nuisance, or an inconvenience that can be handled with another warning sign. That seriously understates the risk. Cyanobacteria can poison pets, make people sick, kill fish and wildlife, disrupt drinking-water supplies, close public waters, and damage the communities that depend on them. The risks are real, the harm is happening now, and by the time the public recognizes the danger, the bloom may already be established.

Blue-green algae is not actually algae. It is cyanobacteria, and some types produce powerful toxins. Blooms may resemble spilled green paint, pea soup, floating grass clippings, foam, or thick green, blue, brown, or black mats. Wind can push the material into coves and along shorelines, creating highly concentrated pockets in the same shallow water where children play and dogs drink. When water becomes discolored, develops a paint-like film, smells unusual, or collects thick scum along the shore, the problem is no longer cosmetic. It is a warning to stay out. 

The Risk Reaches Far Beyond the Shoreline

Dogs are often the first in the water and among the most likely to ingest dangerous levels of cyanobacterial toxins. Nothing tells them that green scum or discolored water may be unsafe. They gulp warm shoreline water, bite at floating mats, swim through scum, and then lick contaminated water from their coats. By the time an owner notices vomiting, excessive drooling, staggering, tremors, weakness, or difficulty breathing, the poisoning may already be severe. Depending on the toxin, symptoms can develop within minutes or hours. 

Many people are unaware of the different ways cyanotoxins can make them sick. They can cause skin and eye irritation, stomach illness, coughing, numbness, weakness, and damage to the liver or nervous system. Exposure can happen through swimming, swallowing contaminated water, or breathing tiny droplets produced by spray and wave action.     

Think you have to swim in contaminated water to be exposed? Maybe not. Researchers in Florida have detected cyanobacterial toxins and related compounds in the air near bloom-affected water, suggesting that wind and spray may carry the danger beyond the shoreline.  Scientists are still determining what repeated exposure may mean for people, but the finding is unsettling: someone may be breathing bloom-related toxins without ever stepping into the water. 

The questions do not end with rashes, vomiting, or liver damage. Scientists are now asking what repeated exposure could do to the brain. In a 2025 study of dolphins from Florida’s Indian River Lagoon, one cyanobacteria-linked neurotoxin was nearly 2,900 times more concentrated during bloom season. The dolphins also showed Alzheimer’s-like changes in their brains. The study does not prove that cyanobacteria cause Alzheimer’s in people, but it raises troubling questions about risks we may still be underestimating. 

And this is not just a U.S. problem. Toxic cyanobacteria are closing lakes, threatening drinking water, and putting people and animals at risk around the world. The World Health Organization now treats bloom prevention as an important public-health priority.  

Warning Signs and Closures Are Not Bloom Control

Across the country, health departments and water managers are already sampling water, posting advisories, closing beaches, and warning people to keep pets away when blooms are identified. That work is necessary and protects the public, but it begins after the problem has developed. By the time a sign goes up, cyanobacteria may already be established, pets and wildlife may already have encountered it, and families and businesses may already have lost access to the water. A warning protects the next visitor. It does not control the bloom, restore the water, or stop it from returning.

Monitoring tells us when the danger is present. It does not make the danger go away.

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A Fast Chemical Knockdown Has Consequences

Many lake, reservoir, and water-system managers go a step further and apply chemicals or algaecides to kill an active bloom. They can knock down visible growth fast. That speed is why they are widely used. But clearing the green water today is not the same as fixing what happens beneath the surface or preventing the bloom from coming back.  

Some algaecides rupture cyanobacteria cells, popping them open like water balloons and releasing the concentrated toxins stored inside them into the surrounding water. For dogs that drink directly from bloom-affected water, that sudden release can make an already dangerous situation worse. EPA guidance also notes that certain algaecides can harm zooplankton, other invertebrates, and fish. 

Just as concerning is the damage repeated chemical treatments can cause beneath the surface. Broad-spectrum algaecides often kill beneficial bacteria along with the bloom. These microbes are nature’s cleanup crew: they consume dead algae and sludge on the lake floor, reducing the nitrogen and phosphorus available to fuel more growth. Killing them can lead to faster, more aggressive bloom rebounds.

Copper sulfate, one of the most commonly used algaecides, creates another long-term problem: the copper does not disappear when the water clears. With repeated treatments, it can build up in bottom sediment, where it can harm fish and other aquatic life.    

Each chemical application sets off another cycle of purchasing, storage, handling, dosing, and retreatment. When the immediate effect fades, the phosphorus, nitrogen, warm water, and sunlight that fueled the bloom are still there. The water may look better for a time, but the conditions that created the problem have not disappeared.

We Cannot Keep Waiting for the Long-Term Fix

Years of fertilizer runoff, stormwater, wastewater, and decaying organic matter have filled many lakes, ponds, reservoirs, and other water systems with the excess phosphorus and nitrogen cyanobacteria thrive on. Stopping more fertilizer and polluted runoff from entering the water matters. So does dealing with the phosphorus already in the water and sediment, rebuilding damaged shorelines, improving stormwater controls, and using beneficial bacteria or circulation where they make sense. No two water bodies need exactly the same plan.  

The problem is that many of those improvements take years to plan, fund, and implement. Meanwhile, the bloom is already happening. Dogs are still playing in the water, beaches are still closing, fish and wildlife are still being exposed, and communities are still relying on repeated chemical treatments for temporary relief.

Long-term restoration is essential, but it cannot become an excuse for leaving the current risk unaddressed. Communities do not have to choose between immediate action and a broader restoration plan. They need both.

Ultrasound Can Be Deployed Now

SonicPure’s ultrasound technology can be deployed now and run continuously while the longer-term work moves forward. The Pulsar 4400 sends 4,400 targeted ultrasonic frequencies through the water, disrupting the buoyancy cyanobacteria need to remain at the sunlit surface and dominate the water. It combats active blooms and suppresses future blooms without adding algaecides or other chemicals to the water or leaving behind toxic residues. 

Unlike a fast chemical kill, SonicPure ultrasound does not burst the cells and dump their toxins into the water all at once. The cells sink, die, and break down gradually, avoiding the same sudden toxin release.

Pulsar 4400 — Ultrasonic Algae Control

4,400 targeted frequencies in a 360° pattern, 24 hours a day. Sound waves disrupt cyanobacteria and algae cells. They sink and die. Safe for people, pets, fish, wildlife, and aquatic plants.

Ultrasound also operates continuously. It keeps pressure on cyanobacteria as conditions change, breaking the cycle of visible bloom, emergency treatment, temporary relief, and renewed growth.

SonicPure ultrasound targets the algae and cyanobacteria causing the problem without harming people, pets, fish, birds, wildlife, zooplankton, or aquatic plants.      

It does not remove phosphorus or stop new runoff from entering the water. It is not the entire answer, and it does not replace the longer-term work. Ultrasound does give communities a way to combat the immediate threat while they reduce runoff, tackle nutrient-rich sediment, and carry out other lasting improvements. 

Green scum is not simply an unpleasant part of summer. It is a warning that cyanobacteria may put pets, people, wildlife, drinking-water supplies, and the surrounding community at risk. Monitoring tells us when the danger has arrived. Warnings and closures keep people and pets out of the water. Chemicals can knock it down temporarily. None of those steps provides continuous, long-term control.

SonicPure gives water managers and communities a way to break the cycle of harmful algae blooms, chemical knockdowns, and bloom rebounds while a broader water-quality plan moves forward.

Take action now. Contact SonicPure to discuss how continuous ultrasound can combat active cyanobacteria and suppress future blooms: sales@sonicpure.com or +1 (310) 955-4005.

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