In a commentary also published online, Nancy Knowlton and Jeremy B. C. Jackson, coral experts at Scripps and the Smithsonian Institution, said the new work was notable because it produced data at sites “across a full spectrum of human impacts.” Without this kind of data, they write, studying coral reefs is like trying to discern the ecological structure of the Amazon rain forest by looking at the cattle ranches and soybean fields that have replaced much of it.

Image A small island near the atoll. Credit... Zafer Kizilkaya

Actually, they write, it is even worse. Scientists can still visit vast areas of intact rain forest and have decades of data from earlier researchers. “The situation is very different for the oceans,” Dr. Knowlton and Dr. Jackson wrote, because degradation of ocean ecosystems is so pervasive, and underwater observation is relatively recent. As a result, they said, scientists disagree over the relative importance for coral of local factors like overfishing and pollution as against global problems like climate change and the acidification of oceans it causes.

The Line Islands work will not settle those arguments. But the scientists noted great differences in the fish communities at inhabited and uninhabited reefs, which they attributed to fishing pressure on shark, grouper, snapper and other large predators, said Enric Sala, an ecologist formerly at Scripps and now at the National Council for Scientific Research in Spain.

Kingman is unpopulated  in fact, none of it is permanently above water. Palmyra was dredged extensively in the 1940s, the researchers said, and fishing has occurred there, but today both atolls are protected by the United States Fish and Wildlife Service as part of the Pacific/Remote Islands National Wildlife Refuge. A camp at Palmyra, with a capacity of 20, has its own sewage treatment center.

Tabuaeran, with a growing population estimated in 2005 at 2,500, and Kiritimati, with 5,100 people and growing even faster, are part of the Republic of Kiribati. People there subsist on fishing and have no sewage treatment facilities.