Nancy Knowlton

Sant Chair for Marine Science

National Museum of Natural History


Coral reef biologist Nancy Knowlton had an epiphany that crystallized her understanding of the link between laboratory science and life in the sea. “I was swimming over a newly bleached coral reef,” she recounts, “when I suddenly realized that the patterns I was seeing were perfectly explained by the results we had been getting in the lab.”

She took that inspiration with her from the Smithsonian Tropical Research Institute in Panama to the Scripps Institution of Oceanography in San Diego, where she founded the Center for Marine Biodiversity and Conservation and started Masters and Ph.D. programs in the field. She also took a leadership role in the Census of Marine Life and authored the book Citizens of the Sea to celebrate the ten years of the census.

Now back with the Smithsonian as the Sant Chair for Marine Science at the National Museum of Natural History, Knowlton studies the diversity of coral reef ecosystems and oversees the use of Autonomous Reef Monitoring Systems (ARMS), a technique she pioneered to assess that diversity. 


Likened to condominiums for reef-dwelling organisms, the ARMS are layered stacks of PVC plastic plates that remain on the seafloor for one to three years. “They have lots of little cave-like structures where organisms can crawl in and hide, or they can attach themselves to the plates. It’s a well-defined artificial substrate that attracts both mobile organisms—like crabs and snails—and non-mobile organisms—like sponges and oysters—and is easy to sample.”

The original design of the ARMS used heavy cement structures that required about two weeks to be taken apart. Knowlton made them smaller, simpler to deploy, and easier to disassemble and analyze. “If it takes more than an hour to break down, things start dying,” she says. “The basic concept of the ARMS is to use identical structures that can be placed in all sorts of habitats. It lets us quantify the magnitude of invertebrate and microbial biodiversity across all of our MarineGEO sites and measure changes through time.”

Because the collection methods are standardized, scientists can compare sites around the world using exactly the same methods. “The information from all these individual studies, when taken as a whole, is much greater than the sum of its parts because you can learn from a comparative analysis in a way that you can’t with a single site compilation,” says Knowlton. “That’s the essence of the MarineGEO methodology, observing the same things in many places.” Indeed, the success of ARMS was an important inspiration for the broader concept of a network of sites using standardized research approaches that evolved into the MarineGEO initiative.”

Once the samples are collected, the next step is to analyze them using sophisticated molecular genetics methods to pick up evidence of species based on DNA signatures. “Using DNA to identify things and determine relationships among them has been going on for quite a long time,” says Knowlton. “Then, a number of years ago, we coalesced around a limited number of genes called barcoding genes. Sometimes the gene sequence links to an already discovered species, but if it doesn’t you can use the sequence to trace it to a broader group of relatives. Now, over the last decade, there’s been an explosive increase in the use of Next Generation Sequencing, which lets us target barcoding genes to get hundreds of thousands of sequences of a particular gene from just one sample, which is a major step forward. This research is on the cutting edge.”

Using a community barcoding approach on the ARMS from Florida, analysis of the wealth of tiny organisms turned up over 1,300 species, 90 percent of which were not in existing databases and are probably new to science.  
Taking a reoccurring baseline census of organisms via ARMS collection and DNA identification is one way that MarineGEO monitors environments and how they are performing, says Knowlton. “Quantifying a wide range of life-forms and studying how that diversity is changing through time and across various sites is a first step toward understanding biodiversity so that we can effectively promote resilience in reef ecosystems.” 
As Sant Marine Science Chair, Knowlton leads the Ocean Portal, part of the Smithsonian Institution’s Ocean Initiative to increase the public’s understanding and stewardship of the ocean. A recent inductee into the National Academy of Science and winner in 2009 of the Peter Benchley Ocean Award for Science in the Service of Ocean Conservation, Knowlton continues to break new ground to quantify, understand, and enhance the health of our vital ocean ecosystems.