Robert Paine, a University of Washington professor, propounded his keystone theory in 1966 after studying ochre starfish, or sea stars, as they preyed on the mussel population along the rocky shore of Makah Bay.

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Robert Paine, a groundbreaking, hands-on ecologist who found that removing what he called a “keystone species” from an environment could profoundly affect the fortunes of neighboring species, died Monday in Seattle. He was 83.

The cause was acute myeloid leukemia, his daughter Anne Paine said.

Dr. Paine demonstrated in his field work that certain species exert a disproportionate impact on their ecosystems and that their elimination — as a result of climate change, pollution or some other natural or man-made factors — can produce unexpected and far-reaching consequences for the local environment.

A teacher and researcher at the University of Washington for 36 years, Dr. Paine propounded his keystone theory in 1966 after studying ochre starfish, or sea stars, as they preyed on the mussel population along the rocky shore of Makah Bay, on the tip of the Olympic Peninsula.

After he pried the starfish from rocks with a crowbar and hurled them into the sea, the mussels proliferated along the shore, displacing algae and limpets.

He found a similar chain reaction — or “trophic cascade,” as he called it — when sea otters vanished or were removed from an environment because of fur trading, pollution or marine predators. With the otters gone, sea urchins, which the otters had preyed upon, were free to gobble up a larger share of kelp, food that would otherwise have sustained fish and crabs.

He identified the predator starfish and the otters as keystone species, taking the name from the wedge-shape apex of an arch that keeps it from collapsing.

Dr. Paine, who had a passion for field work, conducted much of his own research on Tatoosh Island, an uninhabited rocky outcropping less than a mile off Cape Flattery, on the Olympic Peninsula. He discovered the spot in 1967 on a salmon-fishing trip.

Simon Levin, an ecologist and professor at Princeton University, wrote in an email that Dr. Paine’s “influence cannot be overestimated,” particularly his “notion that to understand systems one had to perturb them.”

“He helped make ecology an experimental science,” Levin wrote.

Dr. Paine quickly achieved a stature in the scientific community that matched his 6-foot-4 frame. Several months after he published his seminal paper on keystone species in the journal American Naturalist in 1966, he received a letter from Robert MacArthur, a leading ecologist at Princeton.

“This changes everything,” MacArthur wrote.

Robert Treat Paine III was born in Cambridge, Mass., on April 13, 1933. His father, also named Robert, was a curator at the Museum of Fine Arts in Boston and a descendant of Robert Treat Paine, a Massachusetts lawyer who was a signer of the Declaration of Independence. His mother, the former Barbara Birkhoff, was a writer and photographer.

His marriage to the former Alice Coleman ended in divorce. In addition to his daughter Anne, he is survived by two other daughters, Susan Paine and Nancy Paine; five grandchildren; a great-granddaughter; and a brother, Garrett.

“All my early childhood memories involve biology,” Dr. Paine said in an online interview with the University of Washington’s biology department. “I remember sitting in the dirt driveway when I was around 2½ years old and watching ants. I was utterly fascinated with nature from a very young age.”

That fascination, along with an interest in birding, propelled him toward a study of fossils as a paleontologist and geologist. After graduating with a bachelor’s degree from Harvard University in 1954, he served in the Army and then pursued graduate studies at the University of Michigan.

But at Michigan he shifted his focus, from extinct to animate objects, after taking a revelatory course on freshwater invertebrates given by the naturalist Frederick Smith, a faculty member. Inspired, he went on to earn a master’s degree and a doctorate in zoology.

He joined the faculty of the University of Washington in 1962 and was promoted to professor in 1971. He retired in 1998, but returned to campus regularly and established an endowment to support graduate research.

Dr. Paine preferred field work, as Jennifer Ruesink, a biology professor at the University of Washington, wrote in a tribute to him on the university’s website:

“Working on a remote island was not easy: leaps of faith across surge channels, slippery algae that could take down the most sure-footed, boats overturned and scientists bodily moved by rogue waves, all supplies hefted from the beach to the top of the island via a hundred homemade steps.

“Every two weeks during the summer,” she added, “when the tides reached their extreme lows, and at longer intervals in winter for tides in the dark, Tatoosh Island had its vital signs checked and challenged.”

Dr. Paine found great value in deliberately disrupting an environment in the interest of science, as he did on Makah Bay, when he threw the predator starfish into the waves, away from the shore. “Experimental manipulation is not only more interesting, it’s much more fun,” he told The Seattle Times in 2013. “And getting results you can interpret, if you test an idea — that’s what science is all about.”

He continued to teach well into his later years and produced a dynasty of ecologists. “All my students were smarter than me,” he was quoted as saying in a 2013 profile in The Atlantic magazine, “but just less knowledgeable.”

One former student, Peter Kareiva, director of the Institute of the Environment and Sustainability at the University of California, Los Angeles, wrote of Dr. Paine in an email: “He insisted on experiments in ecology at a time when others were content with simply explaining patterns. I think he turned ecology from quantitative natural history into a modern science.”

Later in his career, with his concerns about the impact of human activity on the environment growing, Dr. Paine came to recognize the most crucial keystone species of them all.

“Humans are certainly the overdominant keystones,” he said this year in the science journal Nautilus, “and will be the ultimate losers if the rules are not understood and global ecosystems continue to deteriorate.”