WILLIAM J. BROAD


In 1953, when Sylvia A.Earle began studying algae, the marine plants and related microbes were often considered weeds or worse. Boaters ridiculed them as scum that turned patches of sea into pea soup.

Today, Dr.Earle notes that just one type - Prochlorococcus, so small that millions can fit in a drop of water - has achieved fame as perhaps the most abundant photosynthetic organism on the planet. It daily releases countless tons of oxygen into the atmosphere.

The tiny organism is estimated to provide the oxygen in“one in every five breaths we take,”Dr.Earle said in an interview. And it is just one of thousands of types of marine algae and photosynthetic microbes.

A student of the big and the small, Dr.Earle is a co-author of“Ocean: An Illustrated Atlas,”published recently by National Geographic. Its maps and graphs, prose and pictures detail how discoveries like the surprising ubiquity of Prochlorococcus are illuminating the sea, its immense impact on the planet and its habitability.

Dr.Earle, an oceanographer and former chief scientist of the National Oceanic and Atmospheric Administration, has participated in more than a half-century of ocean exploration and protection.

She was involved in former President George W.Bush’s designation in January of vast parts of the Americancontrolled Pacific Ocean as marine monuments. The new protected areas - including the ocean’s deepest spot, down nearly 11 kilometers - cover about 500,000 square kilometers.

Her knowledge makes her well qualified to reflect on what is still unknown, as she does repeatedly in the atlas.“What’s astonishing to me is how fast the insights are coming,”she said.“It’s the greatest era of planetary exploration in all of human history. And we’ve tried to cram it between two covers.”

She and her atlas have many fans.“There’s no one else like Sylvia,”said Marcia K. McNutt, director of the Monterey Bay Aquarium Research Institute in California.“She’s one of these rare combinations of energy, passion and eloquence.”

Sylvia Alice Earle, 73, grew up on a small farm in southern New Jersey and spent summers at the beach. For college, she went to Florida and fell in love with ocean research. She graduated in 1966 with a Ph.D. from Duke University in North Carolina.

Her love of plant life is reflected in the atlas’s portrayals of algae as well as a beautiful map that reveals the ocean’s highly variable concentrations of chlorophyll - the green pigments that power most photosynthetic organisms. Remarkably, the satellite map shows chlorophyll hot spots in the icy waters around the North and South Poles.

Beyond Florida, much of her early research focused on coral reefs, which live in symbiosis with tiny algae. On a 1964 voyage, she studied the western Indian Ocean.“We went to places where nobody had dived before,”she said.“There aren’t many like that today.”

In the 1980s, she helped found two companies to make innovative vehicles that could open the sea’s dark recesses to human exploration, and ever since has sought to illuminate the abyss.

So, too, the atlas looks at giant mountain chains of the seabed that spew hot lava and power bizarre ecosystems. The wonders include“Lost City,”an area of the Atlantic where volcanic geysers form ghostly spires up to 55 meters high.

While the maps reveal much hidden terrain, the atlas notes that the seabed“is still not as well imaged or mapped as the Moon or the surface of Mars.”

Over the decades, Dr.Earle has increasingly moved beyond exploration to spend time on issues of oceanic destruction and conservation.

Dead California sea lions dangle topsy-turvy from a gill net in a gruesome photo. The caption notes that more than 300,000 marine mammals are estimated to die annually in fishing gear. A mosaic shows the scores of debris removed from the digestive tract of an albatross chick after its diet proved fatal.

Recent events, Dr.Earl and her coauthor, Linda K.Glover, write in the atlas,“have shattered the notion that the ocean is so vast, so resilient, there is little humans can do to alter its nature.”

Echoing the arc of her career, the atlas details the growing efforts to create marine sanctuaries and protected areas around the globe. Research, it notes, reveals that fully protected areas can produce greater numbers of larger fish and greater diversity in only five years.

The explorer in Dr.Earle lives on, and she dreams of a vehicle that will carry her to the trench’s depths.“If you can go to the deepest place, you can go anyplace,”she said, clearly taken with the thought.“I want to see if we can go deep and learn more about the heart of the ocean.”


PHOTOGRAPHS BY SYLVIA EARLE/NATIONAL GEOGRAPHIC


PETER DaSILVA FOR THE NEW YORK TIMES


In an atlas of ocean geography and biology, Sylvia A.Earle showcases marine life like phylum phaeophyta, left, a brown algae, and phylum chordata, a sea squirt.