Scientist, colleagues share ‘Paerls’ of wisdom

One by one, esteemed researchers stepped to the front of a packed classroom in the UNC Institute of Marine Sciences in Morehead City, North Carolina. Each had stories to tell — of trips to study microbes in the island waters of the Bahamas, warding off frostbite in tents on the Antarctic and combating toxic algae blooms in lakes all over the world.

All these stories centered around the one man being celebrated July 11 by roughly 40 people.

Legendary Carolina scientist Hans Paerl — the William R. Kenan Professor of Marine and Environmental Sciences — retired in July, leaving behind a legacy that extends well beyond his 50-page curriculum vitae and nearly 600 authored papers.

“Hans is an internationally recognized expert, and he’s a real asset to North Carolina and to the United States,” said former Paerl Lab collaborator Jay Pinckney, calling Paerl one of the most influential mentors of his life. “Hans has devoted his life to looking for practical solutions to a lot of water quality problems. Not only that, he’s educated a whole new generation of scientists that are out there being productive and making important contributions.”

The Paerl Lab has been one of the cornerstones of the institute since Paerl joined in 1978. In his 47 years at IMS — more than half of its existence — Paerl conducted pivotal research on eutrophication and harmful algal blooms. He collaborated with environment managers and lawmakers to establish long-term water-monitoring programs and to limit the over-enrichment of waters from agricultural, urban and industrial runoff.

“Hans has been absolutely one of the pillars of the institute,” said Rick Luettich, who directed IMS for two decades. “It’s hard to overstate the impact he’s had in the field. He has done an amazing job of identifying, understanding and documenting drivers of coastal water quality — with North Carolina being his primary laboratory.”

In this 2007 photo, Hans Paerl speaks to members of the Tar Heel Bus Tour about his research. (Melanie Busbee/UNC-Chapel Hill)

A worldly upbringing 

His parents didn’t share his gift for science, but Henri and Anna Paerl passed on an intrepid spirit of adventure to their son.

They hailed from Amsterdam, where they met and fell in love before the start of World War II, which separated the couple before they could marry. She participated in underground resistance efforts in Amsterdam, risking her own safety by hiding Jews and other persecuted people from Nazi soldiers.

Henri Paerl left the Netherlands to join the British army. Fluent in four languages, he volunteered to pose as a worker in Germany. For two years, he provided secret information to the Allies on where prisoners were being kept — until his identity was discovered.

“He escaped Germany, swimming across the Rhine River into Switzerland,” Paerl said. “I’ve been there, and it’s a very treacherous stretch of water. But my dad was a very good swimmer. He was on the Dutch Olympic water polo team.”

After the war, Henri and Anna married in Holland in 1945. Two years later, Hans Paerl was born.

The Paerl family immigrated to the United States when Hans was 11, settling in San Mateo, California. Though Hans and his sister never faced the dangers their parents did, they grew up with limited resources and quickly learned the value of hard work.

Paerl taught himself English by reading Dick and Jane books, and he worked various odd jobs throughout high school — flipping burgers, delivering packages, cleaning cars. To save money, Paerl attended junior college for two years before transferring to the University of California, Davis.

Working with renowned UC Davis professor Charles Goldman as a graduate student fanned Paerl’s interest in science into a passion for aquatic ecology and limnology, the study of lakes and other bodies of fresh water. Goldman studied many of America’s famous lakes and is an expert on eutrophication — the process by which humans over-enrich waters with nutrients, causing toxic blooms, fish kills and other negative ecological and environmental issues.

Together, Goldman and Paerl studied plankton, algae and the nutrients in Lake Tahoe and developed a nutrient management strategy to help protect its legendary clear, sky-blue waters.

“I thought, ‘This is not such a bad thing. Maybe this is something I want to do,’” Paerl recalled, laughing.

The Paerl Lab at the Institute of Marine Sciences has conducted key research on estuarine waters, where fresh water mixes with salt water from the ocean. (Institute of Marine Sciences)

Building the lab 

When Paerl started work at IMS in 1978, the institute was still a relatively small operation.

UNC-Chapel Hill established IMS in 1947. For the first 20 years, it was known as the Institute of Fisheries Research.

“It really was in that next decade when Paerl showed up that the program diversified into the marine sciences,” said current IMS director Joel Fodrie. “The mission of the institute has always been strongly tied to serving the state, primarily through research. Hans Paerl is an archetype of how you would do that.”

When he first arrived, Paerl had to borrow a microscope from a geologist on campus. But piece by piece, he built up the Paerl Lab into the backbone of the institute.

Much of the lab’s work has been focused on estuarine waters, where fresh water mixes with salt water from the ocean.

“I’ve always had this interest in both freshwater and marine largely because they’re connected,” Paerl said. “Studying them in isolation often is not the most productive way to look at and solve big-picture issues.”

In the mid-’80s, Paerl collaborated with local agencies and lawmakers to establish a long-term monitoring system for the Neuse River Estuary called MODMON. Years later, Paerl established FerryMon, which equipped two N.C. Department of Transportation ferries with devices to track water quality.

Both monitoring systems exist today and provide essential data to understand the impacts of various nutrients on water quality and changes to water quality over time. Through studying the data, Paerl and his team identified the impacts of nitrogen and phosphorous on developing harmful algal blooms and worked with the state to set limits — or a total daily maximum load — on the input of those nutrients.

This work has become even more critical during a time of intensified climate change. In 2008, Paerl co-authored a highly cited paper in the journal Science, “Blooms Like It Hot,” that showed a link between warmer temperatures and an increase in harmful algal blooms.

“Things are changing so fast in the coastal zone, and unfortunately we’re not even able to describe most of those changes,” said IMS colleague Nathan Hall, who will take over MODMON and FerryMon. “The only way you can see if something’s changing is if you have long-term monitoring.”

While Paerl retired from teaching, he’ll maintain his office and a research professorship at Carolina, where he’s worked for 47 years. (Institute of Marine Sciences)

‘My science dad’ 

The retirement party continued that evening, as Paerl played his favorite blues harmonica, surrounded by former students, colleagues and peers.

Among them was renowned University of Georgia marine scientist Mandy Joye ’87, ’89 (MS), ’93 (PhD), one of Paerl’s 68 graduate students and postdocs. At the lab she directs at UGA, Joye constantly talks about Paerl with her students.

“They’ve heard a lot of stories,” Joye said, laughing. “They probably see him as some oversized, almost cartoon figure that can’t be real — like a science superhero.”

Though Paerl retired from teaching, he’ll retain his office and a research professorship at IMS. He plans to spend plenty of time smoking fish, relaxing with wife, Barbara, and playing with his four grandchildren. But he’ll also still work on projects, consult with other scientists and answer phone calls and emails from all over the globe.

His former colleagues rave about his spirit of collaboration and his skill in inspiring people. Paerl believes in working hard and playing hard, as his rocking retirement party demonstrated. He encouraged his students to have fun with their research and offered to get dinner or take walks with them when they were overworked.

Joye said Paerl helped her develop her own belief in herself, encouraging her to make the phone calls that intimidated her, to leave her comfort zone, to take scientific leaps.

“He’s my science dad,” Joye said. “He’s the person I call when I need a sounding board, and he’s just always there. He’s an amazing person. There aren’t enough words to describe the impact that he had on my career. He’s not just an inspiration. He’s a guiding light.”