Annie Bourbonnais has traveled the world to study how elements move through water and affect life in the ocean and on land. She’s been to the Arctic Ocean and Easter Island. But most recently, she’s visited a lot of stormwater detention ponds in South Carolina. 

These ponds nestled behind shopping centers and near parking lots are easy to overlook. But besides preventing floods and reducing erosion, they help keep pollution out of larger waterways. Bourbonnais’ most recent research shows that surrounding a stormwater detention pond with plants can keep nitrogen from going downstream. 

“The plants act like a natural filter,” Bourbonnais explains. “They remove nitrogen, which is both a nutrient and a pollutant. Too much nitrogen in the water can lead to excessive algae growth, which depletes oxygen and harms aquatic life.” 

To reach this conclusion, Bourbonnais, an assistant professor in the School of the Earth, Ocean and Environment, and her Ph.D. student Darcy Perin collected sediment samples and measured the rate at which nitrogen is removed from water.  

Preliminary results have shown that ponds with more vegetation around them have higher rates of nitrogen removal. On the flip side, their research showed that poorly vegetated ponds can contribute more nitrogen back into the water, making them a source of pollution instead of a solution. 

“The more vegetation, the better the pond can filter out pollutants,” Bourbonnais says. “Unfortunately, many ponds are managed with herbicides to keep them clear of plants, but our results show that this can be counterproductive.”

Decoding lake floor mysteries 

But what is the problem with nitrogen anyway? To see for yourself, travel with Bourbonnais to Lake Wateree, a popular recreation spot in South Carolina that has been grappling with toxic algae blooms. High levels of nitrogen in the lake, caused by sewage runoff and other pollutants, have fed these massive growth spurts of algae, which produce toxins harmful to both humans and animals. 

“Algal blooms create a cycle of destruction,” Bourbonnais says. “As the algae grow, they consume oxygen, making the water uninhabitable for fish and other marine life. The sediment at the bottom of the lake becomes oxygen-depleted, which releases more nutrients like phosphorus, and the cycle continues.” 

To combat this downward cycle, Bourbonnais is working with graduate students Archana Venkatachari and Melissa Shugart. They collect water samples from Lake Wateree monthly to better understand how the problem develops. 

“It's a huge challenge, but it’s also an opportunity to use science to improve the quality of life for the community,” Bourbonnais says. “If we can figure out the balance between net nitrogen removal or input within the lake versus input from tributary rivers and streams, we can prevent these blooms from happening.” 

Back to big water 

Looking ahead, Bourbonnais’ research is set to return to larger waterways soon. In the summer of 2025, she will embark on two major research cruises—one in the Bay of Bengal and another in the Gulf of Mexico. The focus of these expeditions is on studying how nitrous oxide, a potent greenhouse gas, is produced in low-oxygen regions of the ocean. 

“This is an exciting area of research because we’re looking at how nitrous oxide emissions and associated microbial communities change under different ocean chemistry conditions,” Bourbonnais says. “Understanding how nitrous oxide is produced and cycled in the ocean can help us better predict and mitigate the effects of climate change.” 

This research involves some deep knowledge of the chemical processes, and it’s easy for the details to muddy the water, but Bourbonnais is working to make her science accessible to a broader audience. She is the liaison at USC for the citizen-run water quality monitoring program WaterWatch on Lake Wateree, and she answers question in the Lake Wateree Association annual meeting.  

She’s also collaborating  with an author to write a children’s book about her research, aiming to inspire the next generation of environmental scientists. 

“I want people, especially kids, to understand that the health of our water systems is vital to all life on Earth,” she says. “The work we do today will shape the future of our planet.”