Can an Ultrasonic Device Burst the Algal Bloom Bubble?

Massive swaths of blue-green in lakes, rivers, and oceans are now a common sign of an unhealthy aquatic ecosystem. The color comes from cyanobacteria, which thrive when agricultural runoff full of fertilizers mixes with warm water. As these blooms of cyanobacteria—commonly referred to as blue-green “algae”—spread, they consume the oxygen around them, killing fish and harming other aquatic life.

City, state, and federal agencies have some strategies to control the blooms: deploying algaecides, requiring no-till farming (which reduces runoff), and increasing circulation in slow-moving water. But these can be expensive, take a long time to implement, and in some cases have negative side effects. For an affordable, more immediate fix, some agencies are now rolling out ultrasonic algae remediation devices that kill cyanobacteria using sound.

How it works

Cyanobacteria and algae are different organisms, but both photosynthesize, emit similar hues, and can harm waterways. Cyanobacteria are more toxic and are responsible for most harmful “algal” blooms (a misnomer), which can cause skin irritation and respiratory issues in humans.

An ultrasonic algae remediation device targets air-filled compartments in cyanobacteria called gas vacuoles. These allow the organisms to float on the surface of water, where they can collect nutrients, photosynthesize, and duplicate. The device—a contraption that also sits on the water—emits sound waves at a low frequency that is harmless to aquatic life but shatters the vacuoles. Without buoyancy, cyanobacteria can’t photo­synthesize and eventually die.

The device can also measure water temperature, pH levels, and oxygen content, all of which influence cyanobacteria growth. Cyanobacteria grow faster than algae in warm water, so tracking rising temperatures helps agencies predict and proactively stymie blooms. It’s also a less expensive solution than copper-based algae­cides, which the Environmental Protection Agency warns can damage a lake’s ecosystem.  

How it doesn't work

The device works best in small bodies of water; the EPA notes that there are limitations on how many acres a single device can remediate. Ultrasonic remediation is no match for blooms in expansive bodies of water like the Great Lakes—even though these polluted, rapidly warming lakes could really benefit from the help. Lake Erie has blooms so profound that NASA can pick up the blue-green swaths from outer space.

Typically, harmful algal blooms occur during summer. Climate change is increasing the number of scorching days, causing lakes to warm at a rate of 0.61°F per decade. At the same time, the amount of nitrogen runoff from farms, golf courses, and yards is also growing. Cyanobacteria are on track to proliferate and will be harder to remediate.

How it could work

Ultrasonic algae remediation devices are a quick fix for the most immediately harmful symptoms of unhealthy waterways and buy time to implement heftier solutions. State environmental agencies from New York to Florida are already using them, some proactively.

After a heat wave in rural South Carolina in 2024, the Department of Natural Resources deployed an ultra­sonic device in a small lake with a history of cyanobacteria. It worked to suppress the anticipated harmful algal blooms as officials planned long-term infrastructure updates that would increase the circulation in the lake with running water.

Ultimately, however, we need to address the upstream conditions that allow cyanobacteria to flourish in the first place.