The Maryland Department of Natural Resources is identifying and controlling toxic algae several ways, from sophisticated imaging to sonic waves
Powered by solar panels, the sonicator buoy sits in Hunting Creek Lake in Frederick County. Photo by Joe Zimmermann/DNR
Robots in the water at Hunting Creek Lake are making it safe to swim.
That’s how Ranger Mark Spurrier said he explains the latest technology at the popular Cunningham State Park swimming hole to even the youngest visitors.
On Labor Day weekend in 2023, one of the year’s most popular times for swimming, the park had to close off all swimming access due to a bloom of cyanobacteria—blue-green algae that, in high concentrations, can be harmful to people and animals.
“That’s what prompted us to push to get these buoys,” Spurrier said of the park’s new tool to prevent harmful algal blooms. “We want to control it the best we can.”
In June, the park installed two buoys in Hunting Creek Lake, each with ultrasonic transmitters, called sonicators, that use the power of sound to disrupt cyanobacteria blooms before they form.
The lake usually gets a big cyanobacteria bloom in the fall, but so far, the sonicators have worked: There haven’t been any toxin-producing blooms this year at Hunting Creek Lake.
“With climate change, there’s the potential for this to get worse and become more than one in September or one in November. That was the fear,” Spurrier said. “That prompted us to say we have to get ahead of this sooner rather than later.”
At the Maryland Department of Natural Resources’ Science Week in September, department staff presented the sonicators and other technological methods they use to monitor algae and prevent harmful blooms.
Algae are a large and diverse group of organisms that are often very small and found in water. There are more than 1,454 species of algae in the Chesapeake Bay, and only about 2% produce toxins. While they’re commonly known as blue-green algae, cyanobacteria are not technically algae but a single-celled bacteria. Despite their differences in classification and structure, cyanobacteria are informally grouped with algae because of their ecosystem function and ability to photosynthesize.
High concentrations of algae, or blooms, are not always harmful, but some can be dangerous. Certain types of algae produce toxins that can cause serious health problems if touched or eaten. Cyanobacteria blooms can create skin irritants, liver toxins, and powerful neurotoxins, including anatoxin-a, known as “Very Fast Death Factor.” Algal blooms, such as the dinoflagellates that cause mahogany tides, also block sunlight and reduce oxygen in the water, sometimes leading to fish kills and harming plants and other aquatic life.
A microscopic image of Proboscia alata, a type of diatom, a single-celled alga. DNR
The sonicators in Hunting Creek Lake work by applying a low-power ultrasonic pulse to the photic zone, the top layer of water that receives sunlight. This creates a pressure barrier that makes cyanobacteria unable to float up and photosynthesize near the surface. DNR staff monitor the system with an online dashboard, and LG Sonic, the sonicator’s manufacturer, can alter waveforms based on water quality trends and the cyanobacteria species detected.
The technology has also proved successful at Camp Todd, a Girl Scout camp near Denton, Maryland. It was purchased with input from DNR Resource Assessment Services staff. UMD Institute of Marine and Environmental Technology and DNR fisheries biologists reviewed the technology to confirm it wouldn’t be harmful for fish at Hunting Creek Lake. The frequency range of the sonicators overlaps with those used by fishfinders.
The buoys cost $50,100 each, and Spurrier said they were worth the investment, keeping the water safe for swimming and protecting it as a drinking source for the campgrounds and day use area at the park.
High-tech tools for algae monitoring
Climate change and excess nutrient pollution can worsen the effects of harmful algal blooms, leading to more vigilance from DNR and other agencies in monitoring algae.
DNR Resource Assessment Service biologists routinely assess communities of algae, the microscope forms of which are also known as phytoplankton, at 92 stations across the Chesapeake Bay and Maryland’s Atlantic coast. They also monitor 12 state-owned lakes for harmful algal blooms, said Cathy Wazniak, DNR’s environmental program manager who oversees algae monitoring.
Traditionally, identifying harmful algal blooms involves microscopy, where biologists look through a microscope to identify types of algae. This requires highly trained taxonomists and is time consuming to perform. The department is putting several new tools into use to speed up that process.
One new technology is the FlowCam Cyano, a phytoplankton imaging machine that processes a water sample and uses a laser to detect fluorescent emissions from algae, taking micrographs—or microscopic photos—of thousands of algae in minutes. Once scientists build libraries of various types of algae, the FlowCam will be able to differentiate algae by type.
“The goal of getting the FlowCam is to reduce time at the microscope,” Wazniak said. “Detecting blooms will be the first big use for it. Once we have the libraries of algae, it will give us a quick and easy way to detect a bloom.”
DNR is collaborating with the University of Maryland, St. Mary’s College of Maryland, and research teams in neighboring states to build a combined set of algal libraries for the FlowCam.
A DNR staff member demonstrates the FlowCam during DNR’s September Science Week. Photo by AJ Metcalf/DNR
A library of microcystis, a type of cyanobacteria, imaged by the FlowCam. DNR
In addition to the FlowCam, which the department installed in January, DNR acquired another device called the PlanktoScope in June. The PlanktoScope operates similarly to the FlowCam, with a microscope and camera in addition to a computer that runs algae-identifying software, but it’s portable, modular, and can be used on a boat or a truck. The team is also experimenting with the BloomOptix app, which uses a digital field microscope and AI to identify potential harmful algal blooms.
Using traditional microscopy to identify blooms takes time, and with more blooms occurring it’s helpful to have more tools on hand, Wazniak said. When parks notice a potential algal bloom, they notify DNR’s algal bloom team, which tests the water. If the bloom is harmful, DNR will alert state and local health agencies and continue to monitor the area until the bloom has cleared. Most blooms that are harmful in the state are cyanobacteria.
Amy Hamilton, a DNR natural resources biologist monitoring algae, said the department’s algae monitoring tools will help to speed up the identification of harmful blooms and potentially allow for more areas of monitoring. But she said they also reveal the incredible forms and complexity of microscopic life.
Both algae and cyanobacteria are a critical part of ecosystems, providing a key food source for many organisms. Cyanobacteria even played a major role in increasing the oxygen in the Earth’s atmosphere more than 2 billion years ago.
“When you see the photos, you see how different they are and see how beautiful they are—it’s nature’s geometric beauty,” Hamilton said, describing the structures that algae create. “You can look and be amazed by what you wouldn’t be able to see without these tools, what you can’t see in a drop of water.”
DNR asks residents to report algal blooms on the department’s Eyes on the Bay website and to look out for foamy, scummy water of unusual color that may smell like rotting plants. People and pets should take caution and stay away from potential blooms, and people can take steps to reduce nutrient pollution to help prevent harmful algal blooms.
By Joe Zimmermann, science writer with the Maryland Department of Natural Resources.