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Nuts About Nitrogen: AAAS Fellow Deborah Bronk Detangles the Ocean’s Food Web and Pushes for Climate Action

A photo of a woman smiling
Deborah Bronk. Credit: Rachel Kaplan

As a child growing up in landlocked Tennessee and having never actually been to the beach, oceanographer Deborah Bronk collected shells at garage sales and marveled at the adventures of famed explorer Jacques Cousteau.

“I didn’t know any scientists growing up at all. It’s bizarre I’d choose to be a scientist. I just saw them on television,” says Bronk, an AAAS Fellow known for her research advances on the marine nitrogen cycle and leadership in the ocean science research community.

Technically, Bronk explains, “Cousteau isn’t really an oceanographer,” but his Sunday night broadcast and dives into unknown worlds fueled her passion for the deep blue yonder at a young age. 

After high school, Bronk studied marine science and biology at the University of Miami before earning a Ph.D. in marine estuarine and environmental sciences from the University of Maryland.

Along the way, she grew interested in how nitrogen – “the best element in the world,” she says – supports the growth of phytoplankton, microscopic organisms at the base of the ocean’s food web. Phytoplankton are eaten by smaller ocean animals which are then gobbled up by bigger ones.

Nitrogen in the ocean takes different forms. Inorganic compounds, including ammonium and nitrate, exist alongside organic ones, such as the amino acids and DNA left behind when an animal excretes waste or dies. 

Organic nitrogen, originally thought to be unimportant to phytoplankton, exists in high concentrations at the ocean’s surface. Scientists assumed that if organisms could consume them then they wouldn’t persist in such high volumes.

By analyzing nitrogen levels in the water, Bronk uncovered a hidden cycle – cells were taking in the organic compounds, using the nitrogen and then releasing it.

“We need to refine our understanding about the types of nitrogen out there and how they’re used,” Bronk says. “They’re not all the same. Some of them can cause problems.”

For example, she says, nitrogen-rich fertilizer used by farmers in the agriculture hubs of the midwestern United States eventually ends up in the Gulf of Mexico. The nitrogen boom prompts a rapid overgrowth of phytoplankton, which release oxygen when they die and sink to the bottom. This causes bacteria to thrive as they devour the dead phytoplankton and consume all the oxygen. Eventually, the bacteria overtake entire areas and create “dead zones” where nothing else survives.

Healthy levels of nitrogen, however, breed robust phytoplankton and promote the ocean’s overall health, Bronk explains. Through photosynthesis, phytoplankton absorb carbon dioxide – a catalyst for global warming – just like trees and other plants.

“Discovering why climate change is happening and how to fix it is great, and we need to put our money into that,” says Bronk. “But then we need to make the jump from discovery to solution.”

Motivated to do more for the Earth, Bronk took a leave from academia to go to the National Science Foundation where she served as director for the Division of Ocean Science, managing a budget of $356 million.

“When I took the job, I thought it was more money than God,” she said. “It became very apparent that – for a country this size – to only invest $356 million dollars in ocean science is a travesty.”

Adequate funding for ocean research is of the utmost importance to Bronk, currently President and CEO of Bigelow Laboratory for Ocean Science in East Boothbay, Maine.

The lab, funded by grants and private donations, takes an entrepreneurial approach to both research and crafting solutions to problems that can be taken to market.

“When I was in high school, people wanted to go into medicine to save lives,” Bronk says. “Right now, we’ve got to save the planet. We’ve done so much damage for so long and kicked the can down the road.”

One of the lab’s latest projects involves the creation of a supplement for cows to reduce their release of methane – a potent greenhouse gas.

The challenge, Bronk says, is getting the idea from the lab into production and into the hands of thousands of farmers. In contrast, the study of medicine has a defined pipeline for scientists to approach pharmaceutical companies with their ideas.

That clear path for scientists to pitch their innovations to industry doesn’t exist for all fields of work, Bronk notes. 

“We can design a supplement that we think is great scientifically, but if nobody buys it, it’s not going to do what we need,” Bronk says. “If we had the right pipelines already, we could just hand it off to someone.”

As climate change continues to pose a threat for the future, time is of the essence, Bronk adds, emphasizing the urgent need for commercialization of scientific discoveries for global impact.

“There are no easy solutions. I really do believe we’re out of time. It’s only going to get worse, and it’s getting worse a lot faster,” says Bronk. “What better way to spend your life than to figure out how to fix the future?”