Midsummer 1980 saw one of the strongest hurricanes ever recorded in the Atlantic basin. Hurricane Allen wrought damage across the Caribbean, Mexico and the southern US, shattering windows, dismantling houses and flooding roads. But for Dr. Nancy Knowlton, who had been researching snapping shrimp in Jamaica, the experience with Hurricane Allen led to a cascading series of events that would have a lasting impact on her work—and change the field of coral reef science.

The coral reefs in Jamaica were severely damaged in the hurricane. Overnight, the reefs went from a forest of complex shapes to a mostly flattened pavement. When Knowlton saw the damage, she recalls thinking, “Well, I can’t really just keep doing my business as usual, I really need to do something to understand the effects of the hurricane.”

In light of this, she started to shift her research focus from shrimp to corals. But what began as a study of reef recovery became a study of reef collapse as many of the survivors of the hurricane continued to die. Along the way, she realized that what was long considered a single dominant coral species was actually three species. This in turn led to research with Dr. Rob Rowan and then PhD student Andrew Baker on the symbiotic algae, known as zooxanthellae, that live within coral tissues. 

Rowan had discovered that there was an enormous amount of hidden diversity in the zooxanthellae, and so the idea was to study the diversity of zooxanthellae within the newly discovered coral species. Analysis of a handful of samples Knowlton had in her freezer from the earlier work suggested that one of the zooxanthellae types lived only in deeper water, which prompted a large-scale survey in Panama to determine where on the reef the different zooxanthellae types were found.

Then came a coral bleaching event on the very reefs where they had been conducting their survey. Coral bleaching happens when water temperatures get too high, stressing the zooxanthellae and causing the symbiotic relationship to break down and the corals to turn white as the zooxanthellae leave. Without the food provided by zooxanthellae, corals can starve to death, which is why bleaching has been worrying reef scientists for decades. Knowlton compares corals to trees: they are essential to reefs in the way trees are essential to forests, and like trees, they grow really slowly. If they’re harmed, it takes them a long time to regrow. This implies a potentially irreversible degeneration once water temperatures get too high due to climate change.  

Deciphering the puzzling responses of the corals in Panama to the warm temperatures—that some bleached and some didn’t—would become a watershed discovery. It turned out that the hidden diversity of the zooxanthellae explained the bleaching patterns they observed, as the different types of zooxanthellae, which lived in different places, had different sensitivities to warm temperatures.

It is this research that would propel Knowlton’s career to where she would eventually become one of the world’s top experts on coral reefs. It revolutionized the field: it was the foundation of a new discipline, one focused on how increased temperatures from climate change affect coral reefs.

But Knowlton emphasizes that these discoveries were the result of unforeseen shifts—a pattern that she has followed throughout her career, to great success. “I look for the odd things that puzzle me,” she says. “The exceptions are often what lead to scientific breakthroughs.”

In fact, she prefers not knowing exactly what she’s going to work on next.

Favorable Serendipity

After earning her AB in biology from Harvard University and her PhD in zoology from the University of California at Berkeley, Knowlton spent more than 20 years as a researcher in the Caribbean and Latin America. After a stint teaching at Yale, she joined the Smithsonian Tropical Research Institute in Panama, and then, as a professor with the Scripps Institution of Oceanography at University of California San Diego, she founded the Center for Marine Biodiversity and Conservation in 2001. In 2007, she returned to the Smithsonian as the Sant Chair for Marine Science at the National Museum of Natural History. Throughout her career, Knowlton’s research interests were extensive; using snapping shrimp and coral as models, she has studied symbiosis, sexual selection, how species form, molecular evolution, conservation, and more. 

Knowlton achieved this scientific success in spite of the difficulties associated with being a woman in a male-dominated field.  By the time she began her doctoral work in 1972, she says most of the “really conspicuous obstacles” were gone, thanks to women she referred to as pioneers. “But I wouldn’t say it dominated my career,” Knowlton says, adding, “In that sense I think I was lucky.”

One such pioneer Knowlton describes is Ruth Turner, a marine scientist who earned her PhD from Radcliffe College at Harvard in 1954, and whom Knowlton worked for as a research assistant after she graduated from college. Because of the sexist attitudes prominent in science fields at the time, Turner had trouble getting permission to go on research vessels and to have students as a professor at Harvard.

Although Knowlton says her timing getting involved in marine biology enabled her to avoid some of the overt problems other women had faced in the past, she added that that didn’t mean problems were absent. “I felt like I was flying under the radar, and like a lot of decisions were being made in back rooms with no women in the rooms,” she recalls. “It was stressful, actually.”

Knowlton encourages young people considering careers in science to be strategic about where you exert your energy. “Sometimes it’s better to simply put yourself in a more supportive environment than it is to fight a battle.”

 A Legacy of Advocacy

After establishing herself in a male-dominated field (she is the first female recipient of the International Coral Reef Society’s Darwin Medal), Knowlton’s career took yet another unexpected turn: she began focusing on sharing knowledge about the ocean with the public. The reason for this shift in focus, she says, was learning about the importance of positive perspectives.  

While teaching at Scripps, Knowlton noticed that constantly talking about the problems in ocean science wasn’t motivating anyone to make a difference. She described her job as “teaching our students to write ever more refined obituaries of nature,” and knew she had to make a change.

In 2009, she started a lecture series called "Beyond the Obituaries: Success Stories in Ocean Conservation," which was eye-opening for attendees. “People wrote me and said it really changed the way they thought about teaching and research,” she recalls.

The lecture series eventually snowballed into the #OceanOptimism twitter campaign and a global movement called Earth Optimism. The movement encourages people to make a difference by sharing the stories of conservation successes. Run annually since 2017, the Earth Optimism Summit has reached over a billion people worldwide.

“‘Doom and gloom’ pervades the public discourse of ocean conservation,” she says, but focusing on the achievements conservation has made is an important and necessary shift in order to get support.

Her interest in communication has evolved into more general outreach that helps convey the importance of conservation, like authoring a book about marine life called Citizens of the Sea (which inspired her to take up Twitter under @SeaCitizens) and managing the Ocean Portal. She also worked to enhance ocean conservation messages at the National Museum of Natural History with the Hyperbolic Crochet Coral Reef exhibit in 2011 and during the 2013 renovation of the Sant Ocean Hall.  

Knowlton offers some advice for young scientists and conservationists: be flexible, and open to new challenges. “It wasn’t as if I knew exactly what I wanted to do when I was ten years old and went out and did it. I had a very meandering career.”

“You definitely don’t have to figure everything out,” she laughs. “I certainly didn’t.”