At the end of a gravel road, tucked deep into the woods, bald cypress trees dot the shoreline of Bennett’s Mill Pond. Great blue herons wade in the shallows, searching for their next meal. It’s July in North Carolina, and time on the water would be the perfect way to enjoy some peace and quiet. But not today.
Haley Plaas pulls on a pair of rubber gloves. She lays on the dock and gently reaches her hand in. A mucus- like substance clings to her glove as she pulls back, leaving stringy threads on the water’s surface. While brilliant in color, the network of blue scum across the pond is dangerous cyanobacteria, a type of harmful algae.
Sometimes confused with aquatic plants like duckweed, cyanobacteria can vary from looking like green or blue-green opaque, thin mats to translucent paint or dye. Blooms pose a threat to the local environment — leading to fish kills, ecosystem damage, and drinking water contamination. They can also cause illness in humans and death among pets and wildlife.
Harmful algal blooms (HABs) occur naturally, but human activities increase their frequency and intensity. HABs feed on nutrient runoff — anything from leaky septic tanks to fertilizers and industrial waste. While the U.S. South has dealt with this for years, it’s a growing global environmental issue exacerbated by climate change. Increased surface temperatures lead to warmer waters, and more extreme storms are followed by periods of drought. That combination is a perfect recipe for the algae — storms increase nutrient runoff into waterways, and then drought leads to stagnant, warm water.
While cyanobacteria directly impacts water quality, less is known about how it affects air quality. Enter Plaas, a PhD candidate in environmental science and engineering at UNC-Chapel Hill.
HABs emit cells and chemical compounds that travel as tiny atmospheric particles, called aerosols. Plaas has partnered with the Chowan Edenton Environmental Group (CEEG) to deploy PurpleAir air sensors along North Carolina’s Chowan River, part of the Albemarle-Pamlico estuarine system. Their goal is to see if blooms correlate with poor air quality due to an increase in these aerosols, and generate a wealth of accessible data in areas that are underreported.
CEEG educates the public about environmental issues and supports research efforts in the area.
“Water quality is a key issue here. It’s a big part of our livelihood,” says Colleen Karl, chair of the CEEG. “It affects the economy — just look at the number of people that commercially and recreationally fish. Farming is tied into it because they use the water for irrigation, among a number of other reasons. There’s also a lot of people that buy houses in the area because they want to be on the water. So it’s a concern for a lot of people.”
In the study, funded by NC Sea Grant and the Water Resources Institute, Karl engages the community — finding volunteers to host sensors, scouting blooms, collecting water samples, and building local partnerships. Plaas serves as scientific oversight and determines areas to install sensors, conducts lab experiments, and builds statistical models for the data.
Collaborations like this are vital to Plaas’ research.
“By directly collaborating with community scientists you’re connected to a network of people who are seeing these environmental issues every day,” she says. “It’s really important to put community members in the driver’s seat. […] I know this can’t be possible for all research, but for a lot of environmental and public health research it’s crucial to get feedback from the communities that you’re hoping to have an impact in.”